Why IS My Grout Cracking?
This is a common problem that can easily be prevented. Most of the time, there is an underlying problem with the installation or the subfloor rather than the grout itself being mixed or installed improperly.
It is important to understand there are many steps in a proper tile installation.
These are the most common reasons for cracked grout:
Excessive Deflection in the Subfloor or Floor Joists – Movement in your subfloor can cause the grout to crack, and if severe, can cause tile to crack. Is there blocking to prevent the joist from rolling ever so slightly?
Grout that is insufficiently placed in-between tiles – If not enough grout itself is used when or forced between the tiles, the grout may look fine on top but have little strength to stand up to movement.
Improper thin set coverage: When a tile is set into the thin set, if you pull it for inspection, you should see 90% coverage of thin set on the back of the tile. There are several thin set choices
No expansion joints – Because the subfloor in a home is constantly moving with heating and cooling it, you must have expansion joints for the tile to move. Generally we can hide those under trim and you would never know. If you have a long room of tile say 20′ or so, you would want either a piece of metal/plastic trim to break it up or caulking.
Think you can get away with not having expansion joints? Check out this video from the Schluter Systems Tile conference we went to recently. https://www.instagram.com/p/CVAmBYdA2SyBw4IsxKb0IvDAfBo4XEjzKYvCfA0/