Once we’ve learnt how to measure the size of a trowel, how much adhesive will a trowel leave under the tile and which shape of tile trowel to use, is it better to use a u-notched or a square notched trowel, in a previous post –the first part of this article, it is time to keep going on our tiling placement job! In this article we will explain to you which is the best size of trowel to use, how can you calculate the warpage (cupping), in other words, how flat your tile is, to do the right visual inspection and some useful tips to get a successful tiling placement job!
In this article we will explain to you which is the best size of trowel to use, how can you calculate the warpage (cupping), in other words, how flat your tile is, to do the right visual inspection and some useful tips to get a successful tiling placement job!
Which trowel size to use?
Determining which trowel size is correct for your tile placement depends on both the tile itself and the substrate. More accurately, it depends on how flat the tile and substrate are. The less flat the tile is, the more adhesive you need beneath it, which means a larger trowel size.
First you must know how much adhesive you want beneath the tile in the finished placement. A finished placement requires a minimum of 2mm beneath the finished placement, aiming for a 3mm minimum makes it easier to calculate the proper tile trowel size.
There are two basic ways to determine which size of trowel to use: calculating the warpage (cupping) of the tile and substrate or visual inspection.
Calculating the warpage (cupping)
Cupping of the tile means the amount of variation from the plane. What would be the same to say how ‘out of flat’ your tile is. Figure this out by placing the tile face-to-face and squeezing one corner. If the tile is cupped, the opposite corner will not be face-to-face, it will spread apart. Measure the amount of space between the faces of the tile on the opposite corner then divide that number in half. That is the amount of cupping in the tile.
If squeezing the tile in this manner produces a 6mm space between the tiles in the opposite corner, it means the tile is cupped by 3mm. You must add this amount to the minimum adhesive amount you want beneath the tile to get proper adhesive!
If you want minimum 3mm bed of adhesive beneath the tile cupped by 3mm, you must use a trowel that will leave a 6mm bed of adhesive beneath the finished placement. A 12mm square-notched trowel will accomplish the proper coverage in that instance.
Visual inspection is simply fully embedding the tile into the bed of adhesive, then removing it and looking at both the substrate and the back of the tile to determine whether you have proper coverage.
This tile was pushed down only about halfway into the bed of adhesive. Notice the 12mm square notched bed on the left side has the most coverage with the 8mm square notch in a close second. The u-notch in the center has even coverage, but you need a much larger notch to get the same amount of coverage.
When you calculate the amount of cupping in the tile to determine the properly sized trowel, you still need to visually inspect the coverage to ensure you use the proper size of trowel!
Above and beyond using the proper method to get proper coverage for a successful placement, your personal preference will help determine which specific tile trowel you use for different types of placement.
As a rule, the larger the tile the larger the trowel. It is always better to use a larger trowel than you might need for the placement. A little extra adhesive beneath a tile is completely acceptable, not enough adhesive beneath the tile is not acceptable.
U-notched vs. square-notched is a personal preference. While it is easier to obtain complete coverage with a U-notched, you must also use a larger U-notched trowel to achieve the same bed thickness beneath the placed tile. This is sometimes difficult with vertical placements. It is easier to keep a standing ridge on a wall with smaller square-notched than with a larger U-notched.
U-notched trowels make it easier to keep adhesive out of the grout lines as you embed the tile. There is more space between the half-moon ridges with a U-notched than there is with a square-notched. This makes it easier to have the tile drop into the bed with the edge over an open area between the ridges than over the top of a standing ridge. Since the adhesive spreads out, rather than folding over first, it is less likely that adhesive will fill the grout line as you embed the tile.
Now is your turn! What are your tips to choose the right tile trowel size?