How to Mark Guidelines for Installing Tile
Welcome back to another Pro-Follow. I’ve been working with Jim and Rich from Diamond Tile as they tile Fred & Kim’s basement floor, and it’s been great to see how professional tile contractors tackle this job. The guys have finished installing DITRA, and you can read about that process at the link below. Now it’s time to set up guides. This was particularly fascinating because Jim and Rich create a very precise grid-work that enables them to eliminate the need for spacers, make all the necessary cuts beforehand and lay the tile in perfectly even rows.
Step 1: Measure Tile Including Joint
Jim and Rich start by setting out a few tiles with space for the joint. This enables them to get a true measurement along each dimension. For instance, the guys are installing 20″ x 20″ porcelain tile. In reality, these tiles measure 19-3/4″ plus 1/8″ grout joint. With these measurements, the grid spacing is 19-7/8″.
Pro-Tip: Always measure dimensions using tiles from the same batch as the rest of the floor. Don’t use sample tiles or a tile from a different batch number as actual dimension will vary.
Step 2: Measure First Guide
The first two guide lines are the most important because the rest of the grid is based on them. For the first guide, the guys select an exterior wall and measure an equal distance off the wall. Usually, this line is centered on the room. In this case, the guys shifted it (by a factor of 19-7/8″) so that it would span the entire length of the room.
Pro-Tip: Exterior walls are usually more square than interior walls.
Pro-Tip: Shift guide line so that perimeter tiles (cut tiles) aren’t too small and unsightly.
Step 3: Check Distance to Wall
After the guys snapped a chalk line, they checked the opposing wall to see if the two were parallel. It turns out the walls were off by about 3/8″ over the entire length, and that’s pretty good. Small, gradual variations like that won’t be noticeable to the naked eye.
Step 4: Setup Right Triangle
The second guide is perpendicular to the first, and the guys used right triangles to ensure it was perfectly 90° from the first guide.
If you’re not familiar, a right triangle has specific dimensions, and that enables the guys to mark an exact point based off where two lines intersect.
Pro-Tip: The guys often offset measurements by 1″ to avoid using the end of the tape measure.
Step 5: Mark Second Guide
After marking two points, the guys snapped a chalk line, and again, they checked the opposing walls for square / parallel. The guys also checked how the tiles would meet the two support posts. This was important because if a post was completely encompassed by a single tile, it would require an irregular cut. Fortunately, that was not the case, and the guys didn’t need to shift any guides.
Pro-Tip: Chalk lines can easily be erased using a damp sponge.
Step 6: Mark Tile Intervals
The guys based all subsequent guides off the first two, and they marked off points every 19-7/8″.
Pro-Tip: For smaller tile, the guys usually snap a line for every 2 or 3 tiles. These tiles are big enough that they won’t be able to reach more than one tile at a time.
Step 7: Mark Perpendicular Intervals
Jim and Rich repeated the process for the perpendicular guides, marking lines every 19-7/8″.
In the end, the floor was a grid-work showing each and every tile, and these marks are precise enough that Jim and Rich can precut all the tile.
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