Here you are, armed with a sheet of tile and a bucket of tile adhesive; the smell is unmistakable; it’s work and dust. You smear it on, lay down your tile and hope for the best.
That’s where most DIY jobs go awry: Not from lack of diligence by the installer but from using incorrect tool. Does the tile hold? Or does it come loose over time? It depends on the tooth of trowel used to apply the adhesive.
How to Choose the Right Trowel
Surface area and physics is at play here, not opinion. The most critical part of installing any tile are matching your notch depth to the size of the tile. Tiny notches is needed if you are using a small mosaic sheet so the grout lines aren’t filled with mortar. Large slabs of natural stone require a deep square notch to provide a thick bed that will stand up over time. For most ceramic tile used in home floors, a quarter inch square notch is a good compromise between how much material is being used and how well it covers.
If the notch is too shallow, the mortar ridges flaten out from weight of the tile and leave empty space; which isn’t touched by adhesive at all (starving the bond). If the notch is too deep, more expensive mortar go to waste and the tile is hard to hold in place.
Trowel Angle: The other thing about the trowel are the angle. The general rule is that it’s good to hold it at a 45 degree angle, which gives you nice even ridges. If you hold it more flat, then you scrape down into the mortar and your effective bed depth will be thinner different than desired. More steeply angled and you get some weird peaks where air gets trapped.
What you want are nice smooth parallel lines so you can push down on tile and air escapes out from under it. There should of been no hollow spots where it might crack later.
Most folks think that more mortar means more good. Not quite. Too much mortar will force itself into the tile joints and destroy clean appearance of your grout lines (especially with small tiles). On the other hand, large format tiles requires heavy coverage. To avoid mold growth and water damage, they are supposed to be covered at a rate of at least ninety-five percent in wet environments such as shower stalls. For non-wet floors used inside homes, eighty percent coverage is sufficient. More isn’t always better, though! Pulling out a couple tiles while installing them allow you to ensure the coverage rate, which sounds counterproductive but helps ensure you won’t have total failure later.
Another popular question: what’s the deal with mastic vs. What about thinset? The big difference is that mastic is premixed and therefore simpler to apply, while also having significant drawbacks. Avoid using mastic anywhere that gets wet (especially on flooring used for moving heavy items). If something’s going to get wet, or if it’s going to get beat up, you want thinset, which you mix yourself with water.
For example, you’ll definitely want to use thinset when installing tile in a bathroom or kitchen. If you’re using really dense porcelain tiles, such as subway tile, modified thinset provide better sticking because these types of tile don’t absorb much water.
Using the right tool for the job matters because the way you apply the mortar affects how long your project lasts. A bad install might look fine at first, but it will show its true colors under stress.
Pick the right notch. Maintain the proper angle. Make sure you have enough coverage. This protects your floor in the long run.
