Mapei grout issue

[trotterwatcher]

Hi
Ref grouted the whole bathroom last summer with Mapei fast setting mix yourself grout. I used the fast setting, as only have the one bathroom, and need to use it as soon as. It was warm weather and going off quick, so being a diy'er I was mixing small amounts as required, correctly measured out.
I shook the bag, weighed out, mixed with coreect Qty of water, and left for stated time, remixed and went at it. I applied with float, removed excess, waited a while, and sponge off, I didn't tool the finish, as I assume most don't nowadays, I just tided up with the sponge, which left a dry looking even finish. Come 6 months later, parts of it in the wet areas (shower and behind sink) looked like mush, not all but quite a bit.
I re grouted the poor areas again, and as I speak, a couple of bits look the same again. One thing I may have been a little guilty of, is the lack slaking time, as I was probably a bit anxious from the speed it was drying when I did it in the summer. Is this stuff generally good, any suggestions of good premixed small tubs too correct, what are your thoughts please as to what's going wrong, be it my process or not great product? I did also seal second time with aerosol sealer 3 coats, but hasn't looked to have done a lot. Thanks in advance

 

[grantmac]

Yeah, it sounds like the grout isn’t holding up well in the wet areas, which could be a mix of things. Since you mentioned skipping some of the slaking time, that might’ve kept the grout from fully hydrating before application, which can make it weaker. Another possibility is too much water during cleanup—if a sponge was too wet or used too aggressively, it could have diluted the surface, making it break down faster.

Also, grout choice matters. Fast-setting grouts can be tricky, especially in warm weather. Mapei is usually solid, but for showers and other high-moisture spots, an epoxy grout or something like Mapei Ultracolor Plus might hold up better. And if you used an aerosol sealer, those don’t always penetrate deep enough, so moisture might still be getting in.

If it’s just the top layer breaking down, resealing might help. But if it’s crumbling deeper, regrouting with a stronger mix might be the best fix.

 

[trotterwatcher]

Yeah, it sounds like the grout isn’t holding up well in the wet areas, which could be a mix of things. Since you mentioned skipping some of the slaking time, that might’ve kept the grout from fully hydrating before application, which can make it weaker. Another possibility is too much water during cleanup—if a sponge was too wet or used too aggressively, it could have diluted the surface, making it break down faster.

Also, grout choice matters. Fast-setting grouts can be tricky, especially in warm weather. Mapei is usually solid, but for showers and other high-moisture spots, an epoxy grout or something like Mapei Ultracolor Plus might hold up better. And if you used an aerosol sealer, those don’t always penetrate deep enough, so moisture might still be getting in.

If it’s just the top layer breaking down, resealing might help. But if it’s crumbling deeper, regrouting with a stronger mix might be the best fix.

Hi and thanks for the reply, I've done a test piece mock up. I've done a very small Qty to the correct ratio, mixed for the 2 mins stared, rested for the 32 mins stated, and mixed again. The out come 12hrs later was harder to the finger bail, still breakdown with bit of moisture and nail. I'm going to check this ever 12 hrs upto say 72,as I'm unsure of the definitely water proof good to use time, even if it states 5 hrs dry time. I've included a pic of the grout I'd used. Thanks

 

[trotterwatcher]

Hi and thanks for the reply, I've done a test piece mock up. I've done a very small Qty to the correct ratio, mixed for the 2 mins stared, rested for the 32 mins stated, and mixed again. The out come 12hrs later was harder to the finger bail, still breakdown with bit of moisture and nail. I'm going to check this ever 12 hrs upto say 72,as I'm unsure of the definitely water proof good to use time, even if it states 5 hrs dry time. I've included a pic of the grout I'd used. Thanks

The sealer I used wasn't cheap, I sprayed it in the cap and used a small brush to give the grout lines a good dose 3 times, bit great stuff though