Tile trowels are essential tools for applying tile mortar to wall or floor surfaces. But they do more than just move the mortar from your mixing bucket to the installation site. A trowel also acts as a metered dispensing system, delivering just the right amount of mortar for the tile. Understanding this concept is key to understanding type of trowel to use. Tile trowels come in two basic types -- square-notch and V-notch -- and in various sizes for each type of notch.
How a Tile Trowel Works
A tile trowel is similar to other types of masonry trowels in that it has a handle and a flat metal plate and is designed for scooping up and spreading mortar onto a relatively smooth surface. It's the notches in tile trowels that make them different. The notches do two important things. First, they make it easy to apply only a specific amount of mortar. No matter how much mortar you pile onto the trowel, the notches apply it in nice, even lines of identical thickness. Second, the trowel creates spaces between the lines of mortar. These allow air to escape when the tile is pressed into the mortar. Without the spaces, you could get air pockets that prevent the tile from lying flat or adhering properly.
Square-Notch Tile Trowels
Square-notch trowels have square or rectangular notches that create mortar rows with flat spaces between them. They typically dispense more mortar than V-notch trowels, and the spaces between rows leave more room for the mortar to smush down.
As a general rule, square-notch trowels are used for most floor tile and any tile over about 2 inches square. A variation of a square-notch trowel is the U-notch trowel. This delivers a bit less mortar than a square-notch and can be used wherever a square-notch makes sense.
V-Notch Tile Trowels
V-notch trowels have a continuous zig-zag or sawtooth pattern with points. They are typically used for small tiles, such as mosaics, or any tiles under 2 inches square. Because V-notch trowels dispense less mortar than square-notch, they are also preferred for many wall or ceiling applications.
Square-notch trowels often have three numbers indicating the size and spacing of the notches. The first number is the width of each tooth; the second is the spacing between teeth; the third is the depth of the teeth. For example, a 1/4 x 3/8 x 1/4-inch trowel has 1/4-inch-wide, 1/4-inch-deep teeth spaced every 3/8 inches. If only two numbers are given, the first indicates the width of the teeth and the spacing (which will be the same), and the second is the tooth depth.
V-notch trowels typically have two numbers: first, the width of the notches, and second, the depth of the notches.
Choosing a Notch Size
Choose a notch size based on the tile and the installation location. Your tile supplier can recommend an appropriate size for your project. The best way to confirm that you have the correct notch size is to install a few tiles, then lift them up and see how much mortar contacts the tile and the underlying surface -- known as the coverage.
Tile in dry locations should have at least 80% coverage. In wet locations, tiles need at least 95% coverage. This means that no more than 20% or 5%, respectively, of the tile should be dry (without mortar). Regardless of the coverage amount, all corners of each tile must have coverage.