What causes cracked or loose grout?
There are several things that can cause cracked grout and we would be guessing as to the cause. It could be that a field inspection is needed to determine why your grout is cracking. Typically the most common causes are as follows: 1) Excessive deflection in the substrate – this movement can cause the grout to crack, and if sufficiently severe, can cause tile to crack. 2) Grout that is insufficiently packed into the joint. This most often occurs with wall tile. If insufficient force is used while grouting wall tile, it is easy to “bridge” the joint where the grout does not penetrate to the back of the joint. This is especially true if sanded grout is used in joints narrower than 1/8″. The sand grains can easily bridge a narrow joint – in this case the grout may be only on the surface and have little strength. 3) Grout made with an excessive amount of water or polymer additive – the liquid that goes into the grout ultimately must evaporate (except for that consumed by cement hydration).
