QUESTION

Grout Failure - We built our home in 2004/05. We have a slab subfloor with porcelain tile over it. Within just a month of closing, we began to notice the grout crumbling and powdering. We of course, complained to the builder; who had the "spots" regrouted several times.We were finally told it was a normal occurance.Over a 4 1/2 year period the problem became worse, especially in the traffic areas. We had pinhole that turned into voids throughout the family/kitchen areas. This summer, we notified the builder of our intent to sue for "Latent Defects". He had his tilepeople regrout the entire kit/family area. Within 40 days of installation of the new grout the problems have begun again and we are seeing it more in other parts of the house. We suspect we may have some issue with the slab (improper curing or a moisture source). What is your opinion about what we should do next? This is a $600K home with close to $30k in tile work.

ANSWER

ANSWER - Cementitious grout when installed correctly should be hard and last the life of the tile installation.  It should not crumble or powder, which is referred to as punky grout.  Generally when grout is soft and weak it is due to adding too much water to the grout when mixing it and/or using too much water during the clean up that results in pulling too much cement out of the grout.  If the tile was installed over a wood subfloor that is prone to excessive movement (deflection) then that could compound the problem and be a factor.

Since your tile installation is over a concrete slab that is generally much more ridged then I would not expect movement to be contributing to the problem.  If you don't have any loose tiles or cracking within your tiles then I would not expect that your slab has any structural problems.  If your slab has excessive moisture vapor passing through you might get some efflorescence (white residue) staining problems, but it wouldn't hurt the cementitious grout and the added moisture could help your grout get harder. You might not have proper installed movement joints at the perimeters of the room and within every 20 to 25 feet throughout the tiled areas, but that might lead to grout cracking, but not making it become soft.  So I would have to guess that they either used a low quality grout with less cement and/or they used too much water in the grout and during the clean up the first time and then again the second time.

The only way to fully understand your situation would be to perform a forensic investigation to evaluate the tile assembly to determine the substrate conditions and how the tile was installed to determine if it was installed per the industry standards.  Your problem may be limited or there may be other problems that have not been noticed.  It may be necessary to evaluate the grout in a testing laboratory to understand its physical properties and what may have led to or contributed to its failure.

With that said, it may not be practical for you to spend the money to determine what has caused the grout to fail again.  There is always risk when treating the symptom rather than the problem, but if you don't see any other indications of problems then you could re-grout it with the cementitious grout making sure it is done properly the third time, or grout with an epoxy grout that will be more resistant and durable, but is more expensive and problematic during the installation.  For more information on having an investigation performed visit our website at www.CTaSC.com.  Good Luck.