QUESTION

I found your contact info while reading your Construction Specifier Movement Joints and Sealant article, and was wondering if there was a downside to using a “soft joint” material in all the joints.

I have a client that is looking to regrout his patio as the current grout joints are failing all over the patio. He asked if we could fill all the joints with a semi-pliable joint compound and I said I wasn’t sure. As this is an exterior application the product would need to be stable in temps from -30C to +40C

Any guidance you can give in this regard would be greatly appreciated.

ANSWER

ANSWER - First of all, if all the grout joints are failing, filling them with sealant only treats the symptom and not the underlying problem.  So it might not solve the problem.

If the tile assembly is properly installed you can use an ASTM C920 sealant in lieu of cementitious grout with some limitations.  We have tested Dow Corning 795, which is a silicone sealant, in laboratory and determined it performed well with extreme temperatures.   The concern would be if you finish the joints flush with sealant it could be a maintenance problem.  If you rake the joint back the sealant will be easier to maintain, but you have a recessed joint that will collect debris.

By making all of the grout joints resilient movement joints it does provide an added level of mitigating movement within the tile assembly and provides water tight joints.

 

You need to make sure the sealant manufacturer recommends the intended application and that the sealant is installed correctly with backer rod and etc.