How to Level a Plywood or OSB Subfloor Using Asphalt Shingles & Construction Felt

December 10, 2011 | by Fred (email) |

This article is part of our series on How to Install Hardwood Floors.

While preparing to lay 1100 square feet of hardwood flooring, we discovered significant variation in the OSB subfloor that will serve as the nailing surface for the hardwoods. This article provides detailed instructions for leveling a subfloor based on our project.

Project Overview: Uneven OSB Subfloor

subfloor-300The subfloor beneath our first floor is 5/8″ oriented strand board (OSB) laid over 2 x 10 joists that are spaced 16 inches on-center (o.c.). The joists run from the front of the house to a steel I-beam in the middle of the house, and then from that I-beam to the back wall. Each span is approximately 14 feet.

Before we pulled up the previous flooring surfaces (carpet and vinyl), we knew there were some spots on the subfloor with significant peaks and valleys.  Our kitchen, for instance, had a noticeable dip around a cabinet peninsula.  We think the house was built with ‘green’ lumber that may have been exposed to moisture before it was installed. When it dried, the bowing became very noticeable.

Also, every piece of dimensional lumber has a natural crown to it (the direction it bows along the long edge of the wood). The joists should have been laid such that all the wood was “crown up,” but we suspect that several of the joists were incorrectly installed “crown down.” When this happens between two joists that are “crown up,” the depression can be significant.

The depth error in the worst spots on the floor was as much as 3/4″ over about 4 feet. This is well outside the tolerance for hardwood flooring, which should be no more than 3/16″ variation over 8 feet. You can see the dramatic slope on just one part of the floor in this picture. The level is sitting on the crown peaks, with the same measure in a depression between them.


What is surprising about this floor is that the actual OSB is in very good shape. Sometimes, you’ll find OSB swelling at the joists where moisture contacted the subfloor. This wasn’t the case in this house. We did have to replace one piece of OSB due to wood rot where a persistent leak existed, but the rest of the floor was in pristine condition.

If you’re dealing with a swelled OSB situation, we think the best course of action is to use a belt sander to grind down the swelled edge. Just make sure this doesn’t cause any structural instability. If the piece is rotted or just beyond reasonable repair, the best course of action is replacement.

The Solution for Leveling a Subfloor

Searching around the internet for solutions, we eventually landed on this article from Ask the Builder that suggests using construction felt and asphalt roofing shingles to level an uneven plywood or OSB floor for hardwood installation. This was a novel idea to us, but it made sense.  Both roofing shingles and construction felt are dense, not prone to compression (a key element for leveling), and sufficiently thin that they can be used as incremental steps to get to a flat surface.

Since we have such dramatic slopes on the floor, we decided to use the shingles and construction felt solution along with a new layer of 3/8″ plywood. We chose 3/8″ plywood because it is rigid enough to absorb very minor depressions underneath it, and not so heavy as to be unwieldy.

We are planning to lay 3/4″ exotic hardwoods on top of the plywood, so what we’re looking for from the new plywood isn’t an “ultra-rigid” surface, it simply needs to bond to the layer beneath it, absorb very small gaps where the leveling provided by the construction felt and shingles isn’t perfect, and allow sufficient “grab” by subfloor screws to get a tight bond with the 5/8″ OSB below.

To fasten the plywood to the OSB, we considered using a combination of 2″ subfloor screws and construction adhesive (i.e., Liquid Nails for Subfloors). This is generally referred to as “gluing and screwing,” and you’ll see it suggested on some ceramic tiling sites as a method to increase the rigidity of a floor for tile installation. Since we’re going to be laying the 3/4″ hardwoods on top, which itself will entail 15 gauge staples more or less every 18 inches on the floor, we decided to omit the construction adhesive and instead go just with the screws. Our primary motivation was speed and less mess, and so far after walking on the floor, we’re happy with the result.

For the subfloor screws, we used a Senco Screwgun (reviewed at that link) to fasten the 3/8″ plywood to the OSB. The screwgun is an absolute must for this job. We put a screw in approximately every one foot square, which means approximately 1100 screws on this floor. Driving with a drill-driver is simply not an efficient option.

Alternatives to Shingles and Plywood for Leveling

Before getting into all the details of the leveling job, I should say there are other options for leveling a floor. For instance, we could have pulled up the OSB, shimmed the joists underneath, and refastened the OSB to the shimmed joists. This would have the advantage of not putting any additional load on the subfloor, and addressing the cause of the problem directly at the root.

In our situation, however, we believed that this effort would be much more significant than a new layer of 3/8″ plywood, because the problem was pervasive throughout the floor in varying degrees, and as you’ll see from the pictures below, the shingles give a lot of options for how to address a slope over a wide range of floor.  If we were dealing with a single, significant depression in one or two parts of the floor caused by joists being incorrectly crowned, we probably would have opted for this solution since it is much less expensive.

There’s also self leveling concrete as an option for leveling a subfloor. We used self leveler to level the concrete slab in our basement with great success. We opted against this solution on the first floor because most self levelers aren’t rated for installation over OSB, and because they are expensive and messy. Plus, we figured we would need to install 3/8″ plywood over the self leveler to prepare for hardwoods (this may have been overkill, but we weren’t comfortable with the solution of driving staples directly through the leveler). Effectively, the asphalt shingles in our solution are a rigid leveler that we think works as well as any liquid self leveler would have, and they are easier to control.  If you’ve never worked with self leveler, it is a miracle product, but it has its drawbacks, including short work times.

Tools Required for Leveling a Floor with Plywood and Shingles

  • 8 foot level – for getting an idea of where the high and low spots are on the floor.
  • 4 foot level – for moving in tighter areas and judging how level a local area is.
  • String and nails – for pulling a string above the floor both before and after the installation to get floor-wide perspective on the problem.
  • Utility knife with roofing blade (2 knives are nice if you’re working with two people).
  • Tape measure
  • Circular saw (recommended) and/or table saw for cutting plywood.
  • Screwgun (we like this Senco Screwgun with square head driving bit).

Materials Required for Leveling a Floor

  • Asphalt roofing shingles – the 3-tab kind that are about 1/16″ thick (cheapest available is best). You can find these at Home Depot, Lowes, roofing supply stores, and other home stores.
  • 3/8″ plywood – this will be sold as 11/32″ plywood. You will need a sufficient amount to cover the subfloor.
  • 2″ or 2.5″ collated subfloor screws for the screwgun – we used square-head screws – expect 1 screw per square foot.
  • 30 lb. construction felt.

Steps for Leveling a Subfloor

Preparation: Ensure the subfloor is clear, clean, and free of debris, with plenty of space to work. Remove molding and baseboard at the edges so you can get the plywood close to the walls.

Step 1: Determine and mark high and low spots across the floor. We did this two ways, first by dragging our 8 foot level across the floor to try to determine where the high and low spots were in local areas, and then by stretching a string across the whole floor, secured by a nail on each end.  The string does a better job of showing high and low areas across the whole floor. We marked high and low spots using a non-scientific method, sharpie marker on the floor with the words “high” and “low” and sometimes “very low” in the worst spots.


Step 2: Set a strategy for filling in low spots to “even out” the floor. The floor doesn’t have to be level, it has to be flat. Also, it doesn’t have to be perfectly flat – 3/16″ rise or fall over an 8-10 foot area is acceptable.  We decided to start at one end of the floor near the fireplace that had a significant low area and a nearby high area. Near the front of this fireplace, the depression is almost 3/4″, so we’ll have to stack the shingles over one another.


Step 3: Fill in low spots with shingles and construction felt. For our efforts, we decided to use shingles exclusively under the 3/8″ plywood, with the possibility of using the construction felt between the 3/8″ plywood and the hardwoods if necessary.  This can be hard to get perfect, and we found ourselves frequently going back and forth between our 8 foot and 4 foot levels.


If you picture the floor as a topographical map, the idea is to try to fill in the low spots, which may require overlapping some shingles to get to the right depth, and will certainly require cuts… especially since you are always leveling in two dimensions. You can picture that if you were filling a perfectly round depression, you would probably start in the very middle and work your way out, layering shingles until you get a perfectly flat surface.


Step 4: Once the low spots are filled in with shingles, fasten 3/8″ plywood to the surface using 2″ or 2.5″ subfloor screws. Try to hit the joists as often as possible and put the screws about every 12-14″ along the perimeter and about once every square foot in the field. In this picture, Ethan is checking to sure that the shingles underneath my feet are filling the gap in the floor correctly.


We found it best to “dry fit” the plywood in place first, walk on it and have another person use the level to check for uniform flatness.  Once you start putting screws in, you’ll eventually create a very difficult sheet to remove (remember, each piece of plywood ends up with about 45 screws in it if you screw every 12 inches square and along the perimeter).


Step 5: Continue moving out from the first piece of plywood, continually leveling and re-evaluating extended areas of the floor. It is a good idea to regularly check and re-check the height of the floor and to make sure that seams between the pieces of plywood do not create ridges.  Much like regular tongue-and-groove plywood on joists, we recommend staggering the joints on the long edge.


Step 6: Repeat steps 3-5 throughout the rest of the floor.

Floor Loading / Weight Considerations

Any time you are adding weight to a floor, there can be a loading concern.  Most modern homes are built to handle 40 lbs. / square foot average loading, but every house is different, and your individual situation could be very different.  3/8″ plywood weighs about 1.5 lbs. / square foot, so we were not concerned about it.  Asphalt shingles can get heavy, however, especially when filling in a low spot. We think the most weight that would be placed across a single joist with the shingles is about 15-25 lbs along the span, or about 3-4 lbs. per square foot.

In general, plywood does not add strength to a floor, except that it can help distribute the load from the center of a floor to the edges and to nearby joists, which tends to increase strength a bit. If you are at all concerned, it is wise to consult with a structural engineer before trying this in your own home.

Additional Thoughts & Tips

  • Try to avoid relying on the 3/8″ plywood to level the floor. 3/8″ plywood will span about a 1 inch gap before it exhibits considerable localized weakness… Instead, try to use the shingles and/or construction felt to eliminate air gaps between the true subfloor and the additional 3/8″ plywood layer.
  • Remember that the subfloor being “level” is considerably less important than being “flat” – if there’s a slight incline (3/16″ or less) over 8 feet, that will likely be imperceptible to visitors and you especially once furniture is placed in the room.
  • Think of the project as trying to “smooth out” hills and valleys in the floor to acceptable tolerances. Nothing has to be perfect.
  • Plan to lay the hardwood floors across the joists rather than parallel to them. This will further reinforce an even flooring surface.

Does it Work?

Absolutely. Take a look at the finished floor in this space. It’s beautiful, and almost perfectly flat. We’ve had the floor installed for 1-1/2 years now and have had no problems with leveling. Guests marvel at the new floor, not knowing all the work that went into the installation.

117 Responses
  1. Steve says:

    Would expandable foam have a place here? Or is it simply not dense enough to support the weight of the floor? It seems to me that a quantity of expandable foam could be sprayed onto a depression and then you could lay your 3/8″ plywood across it. Allow it to dry before walking on it and it would be okay, right?

    This is just off the top of my head. I’ve never tried anything like that. It just strikes me that it might be lighter than all of that asphalt.

    • Charles Rupert says:

      I thought of the same thing, BUT you have to come up with a way to hold the plywood level until the foam set up. I would use minimally-expanding foam, as you don’t want it pushing your plywood up.

      You could drive indexing screws into the depression to create a series of level support points. You have to fasten the plywood over the foam with screws at some point to keep it flat and secure. Driving screws right next to your indexing screws (so you don’t pull your plywood back into the depression) would work. Not sure it’s worth the effort, but it would likely work.

  2. Deborah says:

    Just the post I needed to see! Thanks so much. We are going through the same thing with The Stone House.

  3. Robin says:

    Great post!! I’m bookmarking this for later. We have a lot of floor leveling to do next year. We were thinking of removing the subfloor and adjusting the joists like you mentioned but this would be a good alternative in some areas.

    Can’t wait to see how your renovation turns out!

  4. Fred says:

    Steve, great question on expandable foam. We thought of that too – seems like something like dense closed cell foam should be an option. Here’s the issues: (1) The stuff you get in a can of “Great Stuff” isn’t hard enough to support flooring traffic. You’d have to get something much more dense, in which case your cost is going up. and you’re probably looking at professional help (2) I think you’d have a lot of difficulty getting the plywood level on top of the foam. The 3/8″ plywood we laid had a LOT of bows and warps in it. The only thing holding it flat was the screws, and the thing keeping it from going to low was the shingles beneath… The problem I see with expanding foam is that there’s no way to get it level… you might be able to get it to harden and support flooring traffic if you were working with a perfectly pre-leveled top-floor, but this just isn’t practical. I’m definitely open to more thoughts on this as its a very interesting idea.

    Robin, as it turns out one of the last areas of the floor near our garage entrance door just couldn’t be done with shingles due to the configuration. We pulled up the OSB and planed the joist underneath about 1/4 inch, then refastened new OSB over that joist. A comprehensive post on that will be up next week, and we’ll certainly link these two posts back-and-forth.

  5. Martin Fennessey says:

    Good article … I’ve been trying to level a floor with shingles and felt … your’s is the only website with pictures of the task … at least it confirms what I’ve been going through … gave up on using the LevelQuik … after finding out from the manufacturer that the water in it could cause the floor beneath it to warp later …

    Good article …


  6. jenny says:

    Hi my kitchen floor one side is higher than the other side. Just like east is higher then the west. what is covered is two layers of sheet vinyl flooring under that is original hardwood. I want to remove all of them before I screw the wood stick
    1.5″ X 3.5″ X 8′ on the house’s beam to level the floor and then use the plywood put on top of the beam/wood stick. Can I do like that or is will be too heavy for the beams ? can I use 3/4″ plywood ? Next to the kitchen is the living room which is the very low spot in my townhouse. can I level the kitchen floor first and then do the living room or do it at the same time? Please help.

  7. Fred says:

    Hi Jenny, How old is the house? What is the beam substructure? That might help, although any answer we give here would just be a guesstimate. You should have a qualified engineer look at the situation. I don’t think you need 3/4″ plywood if you get everything level. We used 3/8″ and it worked great + is much lighter.

    I see no reason why you can’t do them at the same time, and it might be better for the surface of the floor.

  8. jenny says:

    1946 i think the beam isn’t straight. can I send you a pic ?

  9. Terry says:

    Great article and photos using shingles, etc. I have an old (86 years) house that has about a 5/8″ in the center (hallway) 1st floor. I am going to use shingles to level it out. My question is: Do I need another layer of plywood over shingles or can I just install the 1/2″ Engineered hardwood over the shingles? We are going over top of a 3/4″ subfloor and another layer of 3/4″ solid hardwood already and I would rather not add the extra weight, however I fear the floor will be “spongy” in that section?


  10. Fred says:

    Terry – it’s a good question and if it were 3/4″ hardwoods, I’d definitely say your fine with just shingles. We did the plywood because the problem was so pervasive. I don’t think the floor will be spongy – shingles don’t have any “give” to them if you lay them out as we did, so you should be good there.

    • Pat says:

      Do you think The gravel from the roofing shingles might wear off later and produce a crunching sound when you walk on it?

  11. Terry says:

    Thanks for the quick response. I will post my results after completion!

  12. Denise says:

    This was very informative however, I want to put a laminate floor in my finished attic that is about 12×15 square feet. Some of the floor boards are not so level but all are flat. Could I just use the asphalt shingles screwed into the floor boards and joists in the low areas to level the floor without the plywood, followed by the pad underlayment, and then the tongue and groove laminate. I am concerned about adding more weight to the floor of this 111 year old house. Please advise!

  13. Tim says:

    Very informative. After a whole lot of searching this was the best I found. I am much more comfortable taking on this task now. Thanks for the article.

  14. Fred says:

    Denise, you can in fact use the shingles directly below other components. However, if the floor is already flat, are you sure you need to bother leveling it? With a 111 year old house I would be concerned about the weight issue as well.

  15. Jessi says:

    How do you go about removing a section of your OSB subfloor and replace it?

  16. Christine says:

    Hey there Fred,
    Congrats on your article. This method seems much easier then other options.
    My question to you is..Once the floor is finished, do the shingles leave a smell of tar in the house? and are their any danger of some kind of fumes coming from the something that has tar in it??
    Thxs in advance 🙂

    • Fred says:

      Floor has been installed for more than a year and we’ve never smelled any tar, at all – and that basically includes the initial install too. Tar doesn’t smell unless it’s heated, and there’s really no heat in this effort. As for any lasting danger, I don’t think so. Tar is in the pavement we walk on all the time, and this tar is frozen under 1″ of wood after the installation… Obviously, I’m not a chemist/health and safety expert, but I’ve never heard of anyone suggesting danger in tar – and I would think that roofers, especially, would be dropping over dead if there were significant issues. 🙂

    • Terry says:

      We used 90# roll roofing instead of shingle tabs and have been completed for over 2 months with new Hardwood installed over it (in the heat of the summer….No smell whatsoever!

      Good Luck!

  17. Christine says:

    Ive read on a government site that heated tar (very hot) will send out fumes and is a danger for workers. But we dont plan on heating the floor so i’m guessing that you re probably right. And as for it being under wood…asbestos was in the walls and it was a problem. The smell was also a big worry for me so thxs for clearing that up for me 🙂 See you gotta understand that this renovation is for my daughters(mother of 2 babies) fixer upper house… So im thinking like a gramma here lol
    IM thinking that we will go with your idea. It should be cheaper and easier then other methods 🙂
    Thxs so much for your help 🙂

  18. Steve McMahan says:

    Great article, but I have a question about other leveling materials. I know that traditional self-leveling concrete-based materials weight 1 pound per square feet at 1/8″; that’s what it says on the websites. A new product called Levellite weights about 40% lighter.
    I have a large, rectangular room with a short hallway connected and in the middle of the 24 feet length of the room; I have about ¾” out of level and about the same in the hallway. It is a pier and beam construction, 2 by 12’s on 24” centers running that 24 feet length (the room is 17 feet across). I didn’t know that room was out of level before I completed the 5 by 9 small bath room where I put ¼” backer board and self-leveling concrete to resolve a 3/8” out of level in 6 feet of the 9 feet (I hope this isn’t confusing). So, that room is done and very level, and now, I can’t level the house by jacking it up, although I don’t know if it is needed and I need to find a DIY way to level it.
    Can I just buy that Levellite material and pour it over the floor? I have 1” plywood (not OSB) with nails, house was built in 1974. It seems to be the pour method would be quick and easy but not cheap, although I do not know how much I need. Any advice would be great; I can send pics, but I don’t know what they would add other than to show I am not much of a photo taker.

  19. Steve, thanks for stopping by. What type of floor are you planning to put on the surface?

    Do I understand correctly that the dip is in the middle of the room? I am having trouble visualizing based on what you’ve described here.

    If you’re 3/4″ out of level, you’ve got a lot of ground to make up with leveling compound. 1 lb. per square foot for an 1/8″ sounds about right… so if you’re at three quarters inch you’re talking about 6 lbs. / sq. ft. If you get the lighter stuff, maybe 5 lbs. per square foot. Shouldn’t be a problem if the room was built to code (40lbs / sq. ft. live)

    Are you sure you’ve got 2×12 joists spanning 24 feet, though? That’s a longer distance than I’m used to hearing for standard pine – I would have expected no more than 16 feet.

    Note: I’m not a structural engineer, so this is a “best advice for free” situation. Just telling you how I would look at it with the info. provided.

  20. Aaron says:

    This is a great post. I have been trying to figure out what I was going to with my plywood subfloor that runs downhill after a joist. I tore out the carpet to install laminate 12mm flooring and found it to run down hill 3/8″ in 4ft. I can see where it meets up with the kitchen where they had redone recently and they had to build it up to level it also. I think the shingles will be the best option here my one question is should I nail the shingles down before installing the flooring.

  21. Terry says:

    This process worked extremely well in flattening out my 86 year old floors! I tacked the shingles down with a staple gun prior to installing the floor and it worked well. I would offer one suggestion as it seems you have a similar situation as I as far as 3/8″ drop within 5 feet. Be mindful to transition between the shingles and the subfloor as best you can. For example if you need 2 layers of shingles then try and space out the taper length so that it is not as abrupt. I found it very helpful to use 90# tarpaper to help step the transition down between shingles and also between shingle and subfloor.

    My Dad thought I was overanalyzing (and calls me a “clock-maker”), but for the extra hour or so it took it was worth it to make a “smoother” transition.

    Good Luck!

  22. Brian says:

    My subfloors (with new 3/4 plywood) is a mess due to old floor joists beneath. You writeup is going to save me big time! THANK YOU

  23. Steve says:

    My home was built in 1980, and due to poor water drainage over the years the foundation and piers settled quite a lot. For example, the worst areas on the first level were as low as one inch near interior bearing walls. This house has piers running end to end supporting the center of the house. There was no damage to any of the support structure or plywood, just sunken floors due to settling.

    Your website made it possible for me to level my floors in the kitchen, family room, foyer and hall for 3/4in hardwood flooring without any transitions, roughly 1100 square feet. I used asphalt shingles to level the floor, screwed down 3/8in plywood with long drywall screws and covered it all with felt paper before nailing down the hardwood. I finished the project about a year ago and it looks great. The drainage problem under the house was corrected, mildew killed and all new insulation installed in the crawl space.

    Fred, thank you for posting the information on how to do this. I could not and would not have done it without such clear instructions. I tried not to cut any corners. The drywall, interior doors and frames were cut off at the bottom in every room, the base boards were removed and put back with shoe molding, and the water heater and kitchen cabinets were removed and replaced with new.

    Hindsight is 20/20, and given the nature of my particular situation, were I to do this project again, I would probably jack the house up and get it closer to level from the crawlspace before using so many shingles. Shingles would still be needed, but I could have gotten away with fewer, resulting in less time and weight. One inch of shingles is a lot of shingles, and my floors were off in more than one direction in some areas, so the upper layers of shingles were often cut at angles to match the slope. Maybe that was overkill, but that was how I minimized any gaps between the 3/8th inch plywood and shingles. It was a very slow and laborious process.

    Another issue involved how to make enough room for my steel exterior doors to open. I used a belt sander with 50 grit sandpaper to decrease the thickness of the 3/8in plywood in front of the doors. The floor slopes slightly in front on the doors now, but it is completely unrecognizable without a level. In addition, I had to remove the sweep from one door and mount a rubber sweep on the threshold to take up the space and make it air tight.

    So, for anyone surfing the web for answers on how to level (or flatten) your floors, for what it’s worth, this is what I did. It really works. All anyone can see is beautiful, prefinished, hardwood floors, with no clue to what is under the floor or the hard work that went into getting it done.

    Thank you, Fred, and to all who contributed questions and information.

  24. JustME says:

    Brilliant. Our daughter just rented an older home and is hoping to be allowed to redo the floors. I’m thinking this may very well come in handy since most older homes have uneven floors from the home settling.

    • Fred says:

      If you end up laying hardwoods and you have a problem in just a few spaces, you can omit the layer of plywood and put shingles directly below the wood floors too.

  25. Kyle says:

    Awesome article Fred. I’m using it at this very moment to level off the subfloors in my family room, prior to installing 3/4″ Solid Oak Flooring. I started “leveling” the floor yesterday and ended up tearing everything up after realizing that I should have been focusing on getting the floor flat, not level. Anyway, I’m going to give it another shot tonight and have a question for you. My current subfloors are 19/32 OSB, which is not sufficient according to the manufacturer. Therefore, after flattening the floor I will be laying 1/2″ plywood over the shingles. When you laid the second layer of plywood did you lay it parallel or perpindicular to the existing subfloor? I have read conflicting information online and want to make sure I get it right. The existing subfloor was run perpendicular to the joists.

    Also, I have the exact same fireplace setup you have in the photos above. Did you undercut the fireplace or use trim to cover up the expansion gap?

    Thanks for the great article.

    • Fred says:

      Hey Kyle,

      Thanks for reading and for the comment….

      As for the plywood direction, we staggered all the joints but continued to run it perpendicular to the joists. I believe this is the proper way. (Plywood ratings are calculated when the plywood is laid across the joists). In any event, you shouldn’t need the surface plywood for structural rigidity–I suspect the manufacturer wants the thicker surface for nail holding.

      We ran the wood right up to the fireplace and elected not to use any transition strips (b/c we didn’t want the added height). One option we didn’t choose but could have, would have been to turn the boards in front of the fireplace 90 degrees to sort of “frame out” the hearth.

  26. Icarus says:

    Good article. We looked into new floors for the condo and were told that cork is a good solution to help dampen the noise between units. I wonder if this would work even better?

    • Fred says:

      I’m not sure cork would work for leveling. You need to be able to get very thin slats (which the shingles are good for). I’m also not sure whether cork has compression concerns. Have you ever heard of laying cork under hardwoods?

      • Icarus says:

        whoops, i meant using the shingles to help suppress the sound.

        • Fred says:

          Ahh. Nope, shingles won’t help a bit with sound deadening. They make a solid link with the floor below, allowing the sound to travel right through them. Our basement is pretty loud due to the wood floors above.

  27. whippeteer says:

    I will definitely keep this article in mind when the time finally comes to redo the floor in my kitchen. I know I have a slope in the floor due to settling but there are also soft spots under the existing layers of vinyl flooring as well. At 100 years old, I could also be running into some expensive issues.

    • Fred says:

      Thanks for the comment and welcome to One Project Closer!

      Soft spots could be indicative of a poor underlayment. At 100 years ago, you probably have hardwood or softwood slats running perpendicular to the joists, rather than plywood. You may have some repair to do when you pull up that vinyl, just to make sure the house is ready for the next surface floor.

      I hope we’ll make you a regular reader and commenter here at OPC. We love having more people stop by.

  28. Lee says:

    Great, informative article. Really helps with the photos. Would like to go with laminate through out my 30 year old house. After ripping up the old carpet, realized the particle board has several low spots in the living and dining area, and down the hall. Center of the living room slopes toward the walls with a difference of about a half an inch. I believe the low areas are due to constant pet urination (spots every where) and the sloping at the walls, due to the weight. Thought of using shingles underneath the foam underlayment but a floor installer looked at the floor and said it wasn’t as bad as I thought. He suggested more nails because it wasn’t nailed secure enough. Did this on a couple of panels and didn’t notice much difference. I think his real motivation was to sell and install more carpet. With the soiled condition with of the particle board (5/8) would you recommend ripping it up and replacing with OSB, or just using shingles below the underlayment. Sorry for the length of the question. I’ve been accused of over explaining. By the way, what is the recommended distance between screws if I replace the particle board panels. Many thanks, Lee

    • Fred says:

      Lee, welcome! I hope we’ll make you a regular One Project Closer reader…. Ethan’s in the process of documenting a shed building project, and we’re feature a great “How To” on a framed mirror tomorrow. Maybe you should bookmark us?

      Anyhow, on to your questions:

      1) I would replace the OSB where it is soiled, unless it just isn’t that bad, in which case I might cover it with something then use shingles. Pet urine (especially cat urine) can smell even with a surface completely covering it. BTW> Are you saying that you have an actual particle board subfloor, or is it OSB today and you are considering replacing with OSB? I have never heard of a straight particle board subfloor. Not sure that would be code at all.

      2) We put screws about every 12″ – 14″ square – or about 50 screws / plywood sheet. While I don’t think the shingles would move even if you didn’t have the 3/8″ plywood, I felt more comfortable with the plywood layer on top.

      Hope this helps. Best of luck with your project and feel free to come back with more questions.

    • Simon says:

      Lee, my neighbor had trouble with cat urine soaked through carpet and pad as well. He used a spot primer in an upside-down spray can to cover those spots on the subfloor. He checked for odor before installing the new carpet and said it was remedied. Perhaps that’s a suggestion.

  29. Eric says:

    We had to level our dining room floor to lay some laminate wood flooring. Our floor was generally flat until 5 feet from the wall and doorway leading to the kitchen. The drop between the last 5 feet and the wall base was 3/4 of an inch. We used a combination of Luan, 3/8 plywood and shingles to even everything out. Glad i found this article. Thanks for posting your story.

  30. Simon says:

    Fred, great job on the leveling! My wife and I live just South of you in Columbia and are undergoing a similar process. We found our floors to have significant dips towards the edges of the floor which we remedied with LevelQuick in three large spots. The rest is manageable and within 3/16, which we feel we can use layers of #30 on which is roughly 1/16″ thick, I believe. Our joists are 16″ oc, so our dips are not as pronounced. In your mind, do you see any issue going 3 layers of felt – you mentioned it does not compress much at all – for narrow stretches before adding a 10mm laminate perpendicular to the joists. We are not planning on adding plywood on top of flattening the floor for our job.

    Also, when you put down your plywood, did you (need to) leave any expansion gap between the sheets?

    • Fred says:

      Simon, really happy to meet a fellow DIYer in the area! I’ll definitely write back to the email you sent me as well, but as for your questions on this article:

      1) I see no problem with compression with the felt and would be comfortable with that.

      2) You do not need to leave expansion gaps in the sheets. However, you probably should acclimate the plywood before fastening for a few days… then the floor will expand and contract at the same rate as the subfloor, and you should have no issues.

      Our floor is holding up great after nearly 2 years at this point…

      • Simon says:

        Thank you for your opinion on the felt. I think we’ll try a bit of trial and error with a few planks to see what gives and feels spongy with the felt, if anything. Really glad to hear your floor is doing exactly as you want it to.

        Thanks also for the answer on the plywood. I didn’t even think about it expanding together at the same rate with the fastened subfloor.

  31. Vi says:

    When laying your asphalt shingles onto the subfloor… you need to place some space between the shingles to accomodate for any expansion later on?

  32. Anthony says:

    Hello Fred. I have just rented office space on the second floor of a building. I ripped out the carpet and padding from approximately 330 square feet of floor. There are remnants of old vinyl flooring, possibly containing asbestos, and what might be gypsum coating over the vinyl as well as over some areas of the concrete. Of the 330 square feet of floor is approx 64 square feet plywood in an area, the rest is concrete.

    The concrete has some long cracks and it’s obvious that it is not level in some areas. I’m reluctant to use self leveling concrete as I’m not experienced at all with it nor do I want to scrap up vinyl floor that may have asbestos.

    I came across your article as I was researching alternatives to self leveling concrete. I see that your solution works for plywood subfloor but would it work for concrete subfloor? If so, then could I do the following…
    -Level the floor with the roofing material
    -Fasten with cement screws and glue utility grade plywood over that
    -Sand, stain, and coat with polyurethane the utility grade plywood

    The office will have low traffic and it has just enough space for training martial arts (bare foot). Will I have mildew or warping issue if someone spills their water? I realize that I would have to caulk the spaces where the plywood meets.

    Thanks in advance.

    • Fred says:

      I’m sorry for the delay in getting back to you on this question. This is a tough one. On the one hand, my gut tells me to pay for professional removal of the tile to get to a flat, concrete surface, and then to possibly lay a surface that doesn’t require a 100% level floor. On the other hand, I get your idea and maybe that would work… A few thoughts:

      1) If you could get the concrete cleaned, you could put down an epoxy coating or concrete etching stain.

      2) I don’t like the idea of stained plywood. Just doesn’t sound like its going to look good

      3) I think that conceptually the leveling technique may work. If the slab is below grade, I would think you’d want to use pressure treated wood.

      4) Have you considered hardwood flooring over the plywood?

      5) For self-leveling concrete, maybe take a look at this article:

      I know this isn’t a perfect answer. Hope this helps.

      • Maria says:

        Hi Fred- I know this a 10 year old post, but hoping you are still checking replies…

        Your asphalt shingle idea is brilliant. This may work with our master bedroom where the OSB presumably got wet while building the house and sunk in the middle of the room. We will have to do some weight calcs, but hoping it’ll work.

        Now for my question. Our kitchen was built in an old garage. The concrete subfloor slopes 1.75″ over about 25′. It bugs the you know what outta me. I was hoping the asphalt shingle idea would work.

        If we laid asphalt shingles down to level it, then 3/8″ plywood or OSB on top of the shingles, with a click-lock engineered-wood floating floor, do you think that would work?

  33. Troy Davies says:

    I am about to do this myself, but am worried that I will hear crunching from the grit on the shingles. Was this an issue at all for you?


    • Fred says:

      Troy – no need to worry. You won’t be able to hear any grit at all. I shared your concern when when started the process, but once the shingles are locked into place beneath the plywood, they just don’t move at all.

  34. Bret says:

    I think this was a great idea, but I’d seriously question whether it is a safe application for the shingles.

    Everything offgases. It’s not enough to say that the shingles are ‘frozen under a layer of plywood’. I’m sure the joints are not airtight. There is no comparison between exposure to airborne chemicals in an outdoor environment, and the same exposure in an indoor environment where there is little or no air circulation.

    Go to any home improvement store and take a whiff of an asphalt shingle. If you can smell it, it is releasing chemicals into the air. If air circulation around the shingles is poor, those chemicals will build up. I’m not saying I’m an expert, but I’d be careful and/or look for more information.

    • Fred says:

      Bret, I very much appreciate you adding this to the discussion as I had not seen it before. I am still very comfortable with our decision, but I appreciate the additional perspective.

  35. Clayton says:

    I’m in the middle of using this method to level my master bedroom and Bret’s comment got me thinking…I wonder if getting some used shingles from a roofing company would (mostly) eliminate the offgassing. You’d have to know someone or watch for a roof replacement (or call a company to find out where they are working that day) as they throw them away of course.

    In my case I don’t see a problem with offgassing for two reasons (new shingles).
    1. I generally have quite a bit of air circulation between the AC and a ceiling fan.
    2. I’m laying down plywood and then doing the ‘paper bag’ floor look, which will be pretty much air tight.

    Fred, thanks for the great post.

  36. Clayton says:

    As a follow-up to my previous post, after several hours into this project I’ve learned a few things:
    1. If you aren’t putting another layer of wood (like hardwood floors) on top of this second subflooring layer (or whatever the right term is), it is much more important to get the low spots filled in well, and that takes time. I’m doing the paper bag thing (which is awesome), but requires a flat and rigid surface to look best.
    2. Most low spots can be mapped out similar to a topographical map, and doing it this way is very, very useful to me as I’ve done most of it with overlapping layers of tar paper (see #4). I used low, low +, very low, and very-very low. Low is about 2 depths of tar paper. VVL is about a shingle and two tar papers.
    3. Most of the job can be done with overlapping layers of tar paper. Only the lowest spots require shingles. I had several areas that were 3 shingles deep, 80% is in the multiple tar paper category (like 2-4).
    4. Since I’m doing the paper bag treatment and the floors need to be pretty freakin’ flat, every freakin’ screw has to be sunk into the plywood and filled with wood filler, then sanded. More time.
    5. The shingles have a tar bulge running down the middle. You can see it in the photos in Fred’s post above. That bulge sucks and causes issues for people needing to get the floor flat(ter). I cut the shingles into smaller sections and eliminated the tar-ridge part. (more time).
    6. The 1/2 room I’ve done so far is freankin’ flat.
    7. I wish I had a clone of myself, or two. Or maybe just one Fred. Wait, that sounds weird…

    • Fred says:

      Clayton, I wish I could be there to help! What flooring surface are you laying over top of the plywood? Or are you just stopping at the plywood? I’d love to see an after picture (or even a few “during” pictures if you’d like to send them over via e-mail!)

  37. Clayton says:

    Hi Fred,

    On top of the plywood I’m opting for what I’ve been calling the ‘paper bag’ effect, link below. There a several websites detailing the instructions. The short of it is that you:
    Glue ripped up sheets of kraft paper, masking paper, or any paper to the floor, stain (or not), and then coat with a bunch coats (4-6) of water-based Varathane (no smell, fast dry, durable). The surface is supposed to be super-durable and any future defects (scratches, etc) as easy to fix as slapping a new piece of paper down and a few coats of Varathane. You can even sand it if there are bubbles, etc…not that I’ve had many in my test phase…I tried it in my alcove/window area and everybody loves it. My mother saw it yesterday and mistook it for stone at first. I’m never going back to the traditional, expensive crap if I don’t have to (carpet, wood floors, etc).

    I’ll shoot you some “during photos” via email, cell phone quality though. I’m not making a whole photo shoot out of this project (I’m a photographer).
    (just found this one googleing “paper bag floors”)
    (bad photos, good idea)
    (one of the best I’ve found)

    • Fred says:

      Hey Clay – no problem – Phone photos are great. Maybe you can snap phone photos as you go through it, and take a few nice quality “finished” ones! Thanks for sending what you already did. Glad this article was a help to you!

  38. Clayton says:

    Just a short update. Being weekend-only project, I finally finished flattening the floor and I’m super pleased with the results so far. It is FLAT, even better than I hoped for. A few thoughts for others doing this:

    1. Because I’ll be laying a thin coating, I have to lay this down as if I was painting it, so the surface has to be prepped much better than this tutorial/project.

    2. I had to sink the screws into the plywood, which means some minor splintering of the wood around the hole. No big deal, but it has to be sanded (palm sander). The holes left, as all as the small gaps between the sheets of plywood had to be filled with wood putty, and I underestimated the amount needed (about 1.5 of the larger wood putty containers from Home Depot for one room). The putty of course has to be sanded too as it does swell a bit after it dries.

    3. I found myself constantly sweeping and using the shop vac on the floors as I did this. The rocks from the asphalt were a primary culprit and would throw off the level (I used a 8′ aluminum rod from Home Depot, $16…be careful not to bend it!)

    4. The custom cuts were difficult to get under the door trim/casing in come cases as I didn’t remove the door trim (I had JUST painted it and didn’t want to!)

    5. I put in about 9 screws on a sheet first, mostly around the edges, then laid the next sheet down and stood with one foot on each one to check to make sure the edges met. If not, I adjusted with the felt. I think I only had to do this like 5-6 times total.

    6. This is very labor intensive. As in, my back and hands and everything ache.

    7. Two lengths of screws are best for this: some short 1 1/2″ inch ones and some longer 2 1/2 inch ones. The shorter ones for joining the sheets only, the longer ones for hitting the studs. Why not use just the longer ones? Because the shaft at the top of the long screws is bare (no thread) and you won’t be able to sink the screws as the screw portion won’t be touching wood when you are all the way in.

    8. I used a bit thicker (15/32, sanded on one side) plywood, and I’m glad for it. I think it filled the gaps better than 3/8″.

  39. mfjumani says:

    I am trying to flatten one of the floor and at some point I need to use two layers and at some place one layer of shingle. My question is if I put the good under layment on top of these shingles will it make the Laminate floor wavy?

  40. Hi mfjumani,

    I wouldn’t do it, though if you were FANATICAL about leveling using shingles and the felt it might be possible, especially if you just had minor spots to fill. Underlayment is for absorbing very minor areas (like a very small pebble or crack in the sub flooring).

  41. Clifford Shelby says:

    I’ve got a question. First time using roof shingles to level a wood subfloor for a floating hardwood installation.
    My question…….do I lay shingles grit side down, or grit side up (as in roof installation). I started an area with grit side down w/ 3/8 ply on top and got a lot of “crunching” sound when walked on. I reversed how the shingles were laid and the “crunch” sound was not as noticeable.
    Is there a “technical” guideline for which side goes up or down?

    PS Thanks for a great article………….


  42. Fred says:

    Yvette, I’ve never glued down roofing felt before, but I would suspect a construction adhesive would work. Are you putting the felt directly beneath the luan? I assume you are going to staple the luan to the subfloor (as that’s a most common installation method) – my suspicion would be that the roofing felt would be held tight by the staples unless you are planning are major thickness.

  43. Jon says:

    Hi Fred, great guide! I have a quick question, so my flooring is pretty uneven and I started using this method. Did you guys stack up the shingles side by side and then only overlapped where necessary?

    The reason I ask is this, I laid my level down on the floor and found the dips, then I slid a shingle under the level until it wouldn’t slide anymore, then another on top of that, until it couldn’t slide anymore, and so I ended up with maybe 15 shingles overlapping each other but spaced out creating ridges. I thin laid out my level ontop of the overlapped shingles, and, while level, still had gaps under it from the ridges.

    Any help would be great if you have a chance!


    • Fred says:

      Jon, this does happen and that’s why I recommend using the 3/8″ plywood over the shingles. The idea is to get it as supported as you possibly can and then use the 3/8″ plywood to level everything out. 3/8″ plywood is pretty stable to absorb the ridges.

  44. Jon says:

    That makes sense! Thanks Fred

  45. shimiao says:

    Fred, thank you for such a helpful post!
    Just wondering how you nailed down the walnut, using cleat or staple? And whether you encountered any tongue crack/split or not?

  46. Rich D says:

    What a great site. I’m trying to buy a house built in 1978 and the carpet needs to go, this site has been a huge help for my many questions. I’m thinking about doing about 800sq feet total 4 rooms and hall.Thanks so much, I’ll post if I take on this project.

  47. Josh says:

    I have very uneven floors in my kitchen. Would using shingles be better than using strips of plywood as shims between subfloor and 3/8″?

  48. Clayton says:

    In short, absolutely. The shingles will allow you to tame those uneven spots with precision. My bedroom floor was an absolute disaster for level, now it is as flat (and level) as can be.

  49. Rick says:

    Fred, Happy New Year. This appears to be a great idea and methodology. I’m certainly going with this for my project. I am installing 12mm laminate flooring over existing, but old tongue and groove hardwood flooring (not worth refinishing). There does appear to be sheathing underneath the flooring as well and then the joists. There are areas I will need to flatten out, and I wanted to ask your thoughts on using shingles over this type of flooring and not OSB. I also will be installing 3/8″ plywood on top. My feeling is it’s good to go.

    Thanks in advance for your response.

    • Chris says:

      I’ve been using these techniques to great success though I have been quite a bit more exacting with my measurements since I will only be putting down 10mm laminate over my OSB subfloor. I need to get the floor as flat as possible to avoid planks separating. I have a very low depression in my kitchen area that is about 3/8″ to 7/16″ deep over an 8ft span. My biggest problem seems to be that the floors are quite a bit higher at the edges near the walls. With an open floor plan I have been using the masonry line to get a very good idea of just how bad my floors are. I have been using 3/16″ and 1/8″ tempered hardboard to try and do most of the leveling. I did invest in a pneumatic stapler to attach the 30lb felt and save my wrists.

      I am curious though if anyone else has experienced the felt expanding after laying it down and stapling it causing significant rippling. The felt was room temperature at the time I laid it down so I’m not sure why it is doing it.

  50. Tom says:

    Thanks for posting this, I followed your instructions as to using the shingles to level the floor and it worked great. I have a 50 year old UNDER BUILT bungalow style house that I am re doing as my residence. I have a lot of issues with the floors and saggy joists, the floor has 1/2 sags in spots and I am doing engineered flooring through out the house, in some areas I would stack 2 to 3 shingles and taper them down till I was able to create level all the way around the floor. This system worked perfect for my install, especially with the couple bad area’s that I had to work with. Thanks Again for posting this link, it sure helped a lot …… Tom

  51. Steve says:

    Have a 10 yr old house. Want to put hardwood 9/16″ bamboo floors running the length of a 2nd-floor 12′ wide x 24′ long room with a 3/4″ OSB subfloor.

    Right side of the room: joists are correct orientation but 24″ oc.
    Left side of the room: joists perpendicular to right side of room but 16″ oc.

    Some pretty unflat areas, possible some joists are crown up next to others that are crown down.

    Choose the bamboo from a manufacturer for it’s low fume emissions (asthma/upper respiratory problems in household) so can’t use asphalt shingles for leveling. (don’t know if fiberglass would be better? will poke around.)

    1) Would 3/8″ or 1/2″ plywood on top of the OSB be sufficient to handle the 24″ oc joists? Or do I need to pull up the subfloor on the right side of the room and insert new joists in between the original 24″ oc joists? If this is even possible with only access from the top side.

    2) Would I need to pull up the subfloor on the left side and insert blocking between joists oriented across the room’s width to accomodate the flooring ran lengthwise? Or would 3/8″ or 1/2″ plywood on top be sufficient?

    3) If I elect to shim or shave joists to get them nearer level with their neighbor, wouldn’t the existing OSB subfloor pulled up become unusable with the likely breakage around nails or even just nail holes as far as the strength of that OSB along the narrow edge that sits on a joist?

    4) Could I mix OSB and plywood if I am able to leave any of the existing subfloor in place, or should I replace with all OSB or all plywood?

    5) For interior use, should OSB panels have a 1/8″ gap between each?

    Thanks in advance for any guidance/advice you can offer….Steve

  52. Darrell says:

    Instead of stacking sheets of shingles to raise a very low area (3/4 or greater drop), could I use a piece of OSB plywood for fill to get it close, then use levelquick and or shingles to feather out the edges?

    • Pete says:

      I was looking for an answer to this question as well. I have a living room floor that is 1 inch out of level over a span of 20 feet (zero to 1 inch downhill gradually) and at a width of 35 feet. That’s a pretty big area and far more than I’m willing to tackle with a self-leveling product. I was hoping that I could lay down some 1/2″ or 3/4″ plywood at the lowest point to fill in the bulk of the void (then glue and screw it) and then feather out the rest of it with shingles or possibly a self-leveling product. Does this make sense? Any comments would be most welcome.

  53. Gamel Hill says:

    Can I use just the shingles without the felt tar paper under the OSB plywood?

  54. Bob says:

    I just bought a home and took to putting down manufactured hardwood. Lo and behold, the particle board subfloor is a million years old, the house has settled and who knows what else, and the floor isn’t even close to flat (much less level). Then I stumbled across this page. Great resource and very nice information.

    One improvement I’d like to suggest to the general technique is this… Instead of using masons line to determine where the high and low spots are, setup a laser level! An adequate laser level is only about $50. Establish the laser line at some known reference point above the highest spot on the floor. I used 20 inches. Then, crawl around the floor with a tape measure and a sharpie. Measure the distance between the point where the laser intersects the tape and the floor, draw a dot on the floor at that spot and write down the difference (though, be sure your tape measure can accurately take outside measurements or you may be off a 1/16th or so). That is, if the laser is measuring 20 and 3/16 inches, the floor is 3/16 inches too low at that point (based on a 20 inch reference height). Simply grid the floor with dots every 6 inches to one foot (depending on how bad it is), and write the difference right on the floor. When you’ve done the entire room, you should be able to simply connect all dots at the same elevation to see the exact topography of the floor and make a plan for what needs to happen. This procedure is WAY faster than gridding out the room with masons line (i.e. string).

    For me, that was sanding down the high spots to get the entire floor flat to within about a 1/4 inch, and filling the low spots with hardboard and roofing felt. Great article overall, and thanks.

  55. Nia says:


    Thanks for the awesome tutorial and pics. My husband and I are 1st time DIY’ers laying a laminate floor for the 1st time. Right now there is a plywood subfloor that is nailed down. It is very secure. No squeaking, and no water damage. Underneath there is a crawlspace.

    We have several low spots that vary in depth. Most of them being 1/4″, some are 1/2″, there is also a considerable dip. There are a few over the span of 400sq ft.

    We are going to follow this article to a T – EXCEPT where we install plywood over the shingles.

    Here are my questions:
    1. After the shingles are stapled down, can we put 15lb roofing paper over the shingles AND double it as an underlayment for the laminate?

    2. Can architectural shingles be used instead of the 3 tab shingles?

    3. I am afraid to try to nail down plywood myself. Can I skip this step? I was planning on cutting the shingles in the exact shape of the dip using this method:
    What do you think?

    Thank you!

  56. Kent DuFault says:

    Great article. I’m about to put down laminate in a house built in 1905. The wooden sub-floor has significant fluctuations. I really felt that self-leveling compound was not the way to go as it occurs across the entire floor and the subfloor itself is bouncy. This makes sense to me. I had already decided to put down underlayment. The shingles seem like the answer to my dilemma. This is my plan. thank you.

  57. adrian says:

    This article blows my mind. I followed your instructions and it worked perfectly! And not only are they accurate, but your house has the exact same layout and subfloor problems that mine had for the same reasons. I can’t thank you enough for sharing this!

  58. John says:

    I am the 2nd homeowner of a two story house that’s only about 3 years old. One of the bedrooms on the 2nd floor has a dip that is almost 1/2 inch in the center of the room. The room currently has carpet. I lifted up one of the osb boards and did not see any issues with the i-joists. I even contacted the builder and they had an engineer for the company that provided the joists to come take a look and they said it was within tolerance for the amount of deflection. It appears something must have happened during the build as my nook is directly below this bedroom and you can tell that the dip is there by shining a flashlight directly across the top of the ceiling. There are no cracks in the sheetrock which leads me to believe this was there when the house was built.

    What would you recommend to level the floor for carpet?

  59. b. Eisen says:

    We have a second floor bedroom that is 16 feet across. There are lows and highs under the carpet. We were as alarmed and we pulled up carpet and pad. We see that a cement unusual material, now dust and breaking apart was used in low areas. We investigated further by removing tongue and grove plywood in problem low and high areas. There was 34 inch difference to inch difference. The problem appears to originate with joists. Some are bowed up, some down. Are floors are also springy due to nails releasing plywood. We can not get to ends of joists, but have sistered joists with 2 x8 bolted and glued for deflection. But this is on 2 x10 x16 long….every 16 inch. I was worried about load. We do not feel comfortable shimming and planing as we can not go the full joist lengths. Can we use felt and then carpet over again?

  60. Jon says:

    Hi, I have been an avid DIYer for about 30 years now and am having a problem with a sagging floor on the second level of my hundred year old house .there is a beam under the center of the room and the two outside walls are supported all the way down to the ground, but the last wall has no support under it and it has a significant sag (about 1 1/2 inches to 2 inches, I was wondering about using a dense foam wallboard type material to fill the deepest areas and then staggering thinner material as it rises to the wall. And then 3/8strand board over that, the room will be carpeted . What do you think?

  61. mark says:

    I installed self leveling compound over 3/4 in osb. I am installing 5′ wide 3/4 hickory hardwood. I know now that the compound will crack, Can I install plywood over the compound?. Should I use tongue and groove plywood since I can only use screws and can’t glue, except the tongue and groove?Should I use roofing paper over the compound before adding the plywood to prevent moisture?Thanks for any help, Mark

  62. Bill Ladley says:

    Hi Fred,
    I know this is an older post; but it was helpful just the same. I have a similar problem. We are remodeling an old house that was built in 1905. The main structure is supported by 12 x 12 oak beams. Our contractor supposedly leveled the joist to the oak beams (supposedly????); then laid 5/8 OSB. I have found so many peaks and valleys by using my 360 degree laser, a level, and a measuring tape. I actually half areas that have valleys that are 3/16 to 5/16 between peaks that are only 3 feet apart.
    I have a rise of 1&1/2 inch from one side of the house to the other…30 feet. It appears to be gradual with all of the peaks and valleys between. My question:
    I want to lay 5″ x 3/4 Mahogany plank; will your system with the shingles and felt work for my issues? In the past couple of years have there been any new and innovative approaches?

  63. […] How to Level a Plywood or OSB Subfloor Using Asphalt … – This article is part of our series on How to Install Hardwood Floors. While preparing to lay 1100 square feet of hardwood flooring, we discovered significant … […]

  64. Zeke says:

    I think this is a great idea. However, I would suggest having a foundation/ structural inspection by a professional done before doing any work. I am not a pro, and I have not done this to fix an uneven floor yet, but Im going to. My uneven floor was already fixed structurally but not level. So, i am forced with the same “do I pull off the osb that I just put down, and start again?.

    The reason for foundation/ structural inspection.. again, not a pro, but in your case.. you shouldnt have that many dips and rises in your floor. You have some settling issues. Since the fireplace in in the room, and you have a dip there, Id imagine the fireplace isnt supported properly and all that weight is adding to the load bearing wall (if that is a load bearing wall. if its not, then all that weight not on a loadbearing wall I can almost guarantee isnt supported properly beneath it.).

    It is actually not hard to level a house, requires a few bottle jacks 20-30 ton (50 bucks each). I feel that you are doing all this, and are taking a lifetime product (your exotic hardwood) and turning it into a 5-10 year product. Because by not fixing the core issue that is causing the dips and rises, in a few more years, you will start to see the same dips and rises. There are some great youtube videos on how to level a home. again, not an expert, but after hiring someone to fix my foundation wall that was old red brick and crumbling causing a 3” drop in my kitchen floor, I learned enough to be able to do the rest of the fixes.

  65. Don says:

    I’m installing glue down engineered flooring upstairs and the hallway subfloor is 1/4″ lower that the living room. They want it to flow through with no expansion joint or molding where the floors meet. Can I glue down 1/4″ plywood to the plywood subfloor to level it. The floors meet at a big archway and on the hallway side there are two bedrooms and a bath. It’s a big place and I’m stuck, I don’t ever want to do a bad job.

  66. Neil says:

    First make sure the joists will carry a normal floor load. Sometimes the joists in the Attic are only made to carry a ceiling load not a full floor load. Search web for a span table after measuring your 2 by size.

  67. Serge Liss says:

    Fantastic idea! After a whole lot of searching (three weeks sitting on google 🙂 this was the best solution I found. Got even better when job got finished.No smell what so ever. I do admit sniffing shingles on isle two at Lowe’s raised some eyebrows of unsuspected fellow shoppers :)Thanks for the article.

  68. JP says:

    Thanks for all this information… looking for some advice. My house is less than 2 years old. I have an unfinished third floor designed for a live load. The trussed are 24OC except for an area when the egress window is located and the span is ~40″, the trusses are doubled up on each side of this. I’ve wired, insulated, and walled the room and was going to start on flooring when I noticed areas of unevenness. I would be installing floating laminate hardwood over 3-in-1 underlayment.

    I mapped out (contoured) the floor and have regions of 1/8″-1/4″ dips between trusses. However, the larger span area has as much as a 3/4″ dip over 8′. I assume this is only a 3/4″ OSB subfloor. Would you recommend I use the shingle approach or lift up the subfloor and shim the joists?

    • Nick says:

      Who was the half wit that came up with using roofing shingles inside your house,and on top of osb makes it twice as dangerous.
      NEVER EVER use roof shingles indoors as they heat up and break down they will give of gases as they do on top of your roof.Check any hazmat book of any roof shingles and see just how bad they are.Then they what you to lay them on top of OSB really bad.Talking about getting sick and slowing dying this is the way to do it.Besides the fire hazard you would be making.
      Please ask people in their right minds how to do the job the right way.

      • JG says:

        He is suggesting they be sandwiched and used a minor leveling agents in dips, not using entire boxes over an entire subfloor. You’ve also made a strawman argument regarding heat. Roofing shingles get up to 150F in direct sun on a roof and absolutely off-gas as they heat up and less as they age. Up against the underside of interior space is likely to be too cold to release much gas in cold climates and in hot climates where it is air conditioned, it is not hot. In the crawlspace below my house temp never goes above 80F, even when the ambient is 100+F outside. It may be coolor above the subfloor and between the finished flooring closer to my conditioned space. I dont like the idea of using shingles all that much, and if I did I would grab some older ones that have off-gased already, but I wouldnt be afraid to use two or three between plywood and not consider that “making a fire hazard”. Lets all ask the fire responders if we have made our houses unsafe by putting a few asphalt shingles between plywood subfloors. We will get a few laughs I am sure. You’ve taken valid horrible attributes about shingles and applied it on a larger scale to create a scare tactic.

        To others considering this: off gassing is real. Asphalt,mod bitumen,tar, formaldehyde, etc. are all real and VOCs are bad for us and the environment. They are everywhere, in our cleaners, furniture (lots of additives to wood), roads, roofs, many in small amounts and skme places in larger amounts temporarily while it off-gasses. I bought a wood flooring that double complied with the strictest level of VOC compliance internationally, yet I still let the house air out for a few days before I let my baby indoors. You cannot eacape them, and worse, the exposure can slowly accumulate for some people prone to certain medical conditions. They may contribute to medical conditions we are not even aware of. You cannot completely “road tar” your indoor floor and expect a breathable layer of plywood to keep the gas away from you. Do not use hundreds of shingles indoors, especially next to heat sources. I have no fear putting down a few shingles and felt paper on top of a raised wood floor (crawlspace) and under another ply layer, to help with leveling plywood subfloor. Be reasonable, attempt to use common sense.

  69. Al says:

    Great Post Fred

    Do you know if there be any grit crunching noise from the shingles once all installed? I am very concerned about this issue.

  70. Ben Williams says:

    I am also wondering about this. with the grit side faced down in the picture it will be against the subfloor. i was thinking about wherever the shingles are being put down, put a layer of felt down first and then the shingle (if the area is low enough) I hope we can just put the bare shingle down and put a few nails in it. I may just test that myself in an area once i get my flooring and come back here to tell my results

  71. Heather Sierks says:

    Hello. I am a single mom and I just bought a foreclosed home then found out I have 3/4 to 1 inch crowning in my kitchen and living room, so is this something I could do? Do you just put down the shingles in the low areas on top of the existing sub floor then add another layer of sub floor to the entire area?

    • Nick says:

      If you love you kid you will NEVER EVER use roofing shingles indoors,no matter what the reason.Roofing shingles give off dangerous gases.There are so many safe ways to level a floor.Please for your kid and your own safety do not use this shingle method.Also the fire companies will thank you for not making their jobs harder.

  72. Nick says:

    So glad to see your comment on how dangerous shingles are.Can not believe that people would even do this to their own family.They also want to shingle on top of the OSB double trouble,and still not talking about the fire danger.
    Then I had to laugh people wanted to know if the grit made noise.People need to know this is very unsafe thing to do,to hell with it making noise.

  73. Mirna says:

    hello my house is sit on bricks can I use this method to level it ? And it has an old wood floor can I installed on top of ?

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  77. Pink John says:

    In general I like this idea as I just tore out carpeting in a room where I replaced all of the cracked plaster walls with drywall then noticed how uneven the floor was, wish I would have seen it sooner.
    Anyhow, what about using peel and stick floor tile or even sheet vinyl as an alternative to shingles? It would seem to perform the same function, less worry for those concerned about roofing shingles, perhaps more convenient and easier to cut ?

    Thanks for the article!

  78. Mitch says:

    Loved this article! I recently pulled out my carpet just to notice the various low spots that were hidden by the cushion. I am halfway through my leveling stage and can say that it is time consuming with just one person working on it, but the results are amazing. So far, no crunching heard.


  79. Dnelly says:

    I really appreciate you guys efforts in making these notes available. I wanted to ask can I use 3/8 plywood as sleepers every 16″ on center to level or flatten the floor on top of the osb subfloor? Then sheet that with 3/8 plywood and then apply felt on top?

  80. Rachael Nichols says:

    Hi, just ran across your article on leveling floor. My house is over 100 years old and one room is sagging in the middle. I cannot access the underside due to a low crawlspace. Can I use the single method to bring up the center enough to put a new floor down. I was also wondering if weight should concern me.


  81. Tony D says:

    I have a similar condition w/ a 1/2″ gap under my level when i place it across my subfloor. My subfloor is 5/8″ t&g ply instead of OSB. Can i perform the same that you did in this article to help flatten/level the floor? Assume use the shingles to level off and then apply the 3/8″ ply over top it. For clarification. do i screw the 3/8″ into the existing subfloor or do i go into the joists? What size screws do i use?

  82. Mike says:

    Great write up, in the middle of putting down a hardwood floor, pulled up the carpet to fine the floor has many low spots up to ½”. Even found out that one end of the house was not properly set on the foundation. Fixing this has slowed up the job. My subfloor is ½” ply wood, than 5/8” particle board, of all I read on the internet no where it said particle board could not be used unless you searched just asking if particle board can be used. Particle board have been pulled up and OSB going in its place. Thanks for the great write up.

  83. Paul Lammermeier says:

    Great article. Used luan stacked font the low spots and feathered with shingles. Works great. Used 1/2 plywood over,the 15# felt. Thanks for the information.

  84. John C says:

    Hello. Great write up. I have a bathroom redo. There is an area that slopes and I am wanting to level using your method as it is on the second floor. However, if I use the shingles, then 3/8 sub-floor, then hardi backerboard for the tile, is that too much? Could i skip the plywood and just backboard over? Only issue is the thinset application. Thank you for your time.

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