I have brand new grout in a shower done by a pro. Merely two months later it is already cracking. The contractor is telling me that house movement can cause this. (I'm not sure if he's full of it? Can house movements cause cracks in brand new grout? There are cracks happening in multiple directions which is odd for a presumably floated shower. Anyways, the house movement is the only thing I can think of, and my area is pretty notorious for it.
In any case, how would you go about fixing this? Would mixing more grout and driving it in work or would it be a waste of time. I'm really happy with the whole remodel but this is driving me nuts every time I'm in the shower.
Best Answer
Those cracks are due to: 1) too much water in the grout, and/or 2) green lumber.
1) There is a natural tendency to add too much water to the grout mix, because the grout becomes easier to “work”. Each batch of grout is mixed in anticipation to immediate use. Often the installation will be delayed due to a variety of issues. When this happens, the mix will dry out and additional water will need to be added.
There is an ideal cement to water ratio. When it is exceeded, the grout will shrink and you’ll see cracks. If you look close, you’ll see it’s where two planes intersect. That batch of grout was too wet.
2) When green lumber is used, the lumber will slowly dry out (reducing the moisture content) causing the lumber to shrink. It takes about 2-3 months for enough moisture to evaporate to cause the lumber to shrink.
They should have used KD lumber. (The rest of your house has dried out.) Ask to see their invoice from the lumberyard and you’ll see the grade of the lumber. I’ll bet it says “Green” or “S-Dry” and not KD.
The only fix is to wait 18-24 months until the lumber has stopped shrinking...and then re-do the grout.
BTW, the cracks are NOT from seismic movement. Yes, you live in a seismically active area, but cracks from EARTHQUAKES are diagonal or zigzag up the wall.