“Using tile spacers when laying out floor tile will make your grout joints nice and straight … right?” Unfortunately, this belief is commonly held by building owners, homeowners, and even some design professionals, but it is incorrect. As experienced tile installers know, spacers are more likely to hurt the installation than to help it.

How can spacers, which virtually guarantee grout joint uniformity, i.e. grout joints all the same width, be a bad thing? It has to do with the allowable dimensional variation in the size of the tiles and the inconsistency of the wall dimensions across a room. If the individual tiles were all the same size, and if the corners of the room were perfectly square, then spacers might be useful. However, we know that tile sizes vary and room corners are often out of square, so good installers rely on being able to make slight adjustments to the grout joint width in order to maintain grout joint alignment.

According to Table 10 in ANSI A137.1, a calibrated porcelain tile is allowed to vary in its facial dimension by as much as ±0.08 inches, equating to a total variation by as much as 0.16 inches. In other words, tiles could vary in size by over 1/8 inch! Similarly, the wall-to-wall dimension could vary drastically when taken from opposite ends of the room. If spacers are used, the grout joints might have a uniform width, but they simply won’t line up, and the installation will look terrible.

To accommodate the imperfections in the tile and the imperfections in the backing walls, skilled union tile installers are trained to lay out a floor by snapping a grid of chalk lines that will dictate where grout joints will fall. For example, if the tile size is 12 x 12 inches nominal, a tile setter may snap lines every 4 feet in each direction, lining up a corner of the tile on the intersecting grid lines every 4 feet. Then the installer would lay tile inside the grid with grout joints that are more or less uniformly spaced. This will ensure that the joints line up every 4 feet, and within each 4-foot section of floor, there is uniformity. When the tiled floor is viewed in its entirety, all the joints won’t be uniform, but they will be aligned, which is the more important visual consideration.

To the larger issue of layout, the tile setter snaps the grid on the floor in the precise position to eliminate or minimize cut tiles, and it is generally parallel to the longest or most prominent wall in the room. The grid is kept square using the largest possible Pythagorean triple for the size of the room. For example, the installer would snap a right triangle of 8 feet, 15 feet and 17 feet, or a right triangle of 5 feet, 12 feet and 13 feet. In smaller rooms, the triangle may be 3 feet, 4 feet and 5 feet.

Now that we have demonstrated the need for variable grout joint width to maintain proper grout joint alignment, let’s examine what the ANSI standards say about allowable variation in grout joint width. ANSI A108.02 states, “To accommodate the range in facial dimensions of the tile supplied for a specific project, the actual grout joint size may, of necessity, vary from the grout joint size specified.” This language is vague. It does not give a specific value for allowable variation, but it does alert the end user that a certain amount of inconsistency in grout joint width is unavoidable.

In conclusion, imperfect site conditions and manufacturing limitations of tile are two factors that require tile installers to make slight adjustments, which spacers would otherwise preclude, in order to maintain alignment of grout joints. Experienced union tile contractors and installers have the training and expertise to grid a floor, lay out the pattern and provide an installation that looks great even under less than ideal jobsite conditions.


Note: this article is adapted from a previous article by the same author published in 093000 Contractor, the journal of the Tile Contractors’ Association of America.