I just found this forum and have been looking for a solution to my problem. I have a 650sf 3-car garage that's about 25 years old. About 5 years ago (before I had done any research into floor coating systems at all), I had a methyl methacrylate coating applied. The concrete was in good condition (smooth, no cracks, no oil/stains, no obvious water ). No moisture test was performed. The application consisted of the following steps:
1. ground the surface. No bead/shot blasting. vacuum dust.
2. applied color base coat (same 2-part material as subsequent clear coat plus colorant).
3. 1/4" flake complete coat to refusal. vacuum excess flakes.
4. sand flakes. vacuum.
5. clear coat.
6. sand. vacuum.
7. 2nd clear coat.
The work was done in 6 sections, each about 150sf, separated by the expansion joints. The joints weren't filled, but were coated. Each section was dry enough to walk by the time he got back around to it (about an hour). (Maybe used spike shoes -- I don't remember.) There was no odor. ALl the work was done in about 7 hours. It was dry enough to walk on in an hour and contents were re-installed the next day.
All seemed well until about 2 years later when I noticed that some chunks were coming off under the garage door weatherstrips (sticking to the door when it went up). Upon closer inspection, I found that within about 2 ft of the garage door, there were numerous cracks and some efflorescence. Over time, more chips detached, both under the doors and further in, and there were many places that sounded "hollow" where the coating was obviously detached from the substrate. This is in California and dry in the summer. In the winter when it's wet/humid, I frequently see efflorescence in the exposed bare concrete. The "harvested" chips are about 30 mils thick (including the flakes), indicating the overall thickness of the coating. The concrete exposed when the flakes detach is clean and shows no residue from the coating at all.
Except within about 2 ft by the garage doors, the coating seems to be sticking and holding up well.
The contractor that originally installed it is out of business and their warranty excluded efflorescence anyway.
Question is what to do now? I don't think it could be effectively repaired to match, but I guess it could be removed (ground or shot blasted). But what could I do to prevent it from recurring?
If there is, in fact, high water vapor pressure, it seems like I need something that is vapor permeable, but that seems like it reduces the utility of the coating. It's not practical to replace the slab or do any sub slab work.
Would a rougher substrate help (more surface area for the base coat to stick to)? Or some primer/moisture barrier before the base coat? Is MMA an appropriate coating in a garage application? I see mostly "epoxy" (but "epoxy" seems to be used to refer to any 2-part coating system in consumer products without detailing the chemistry actually used, and MMA is a 2-part product.)
FWIW, I paid $4.25/sf back in 2008, which, upon further research, now seems "generous". I have one quote to replace it for $5/sf.
Thanks.
1. ground the surface. No bead/shot blasting. vacuum dust.
2. applied color base coat (same 2-part material as subsequent clear coat plus colorant).
3. 1/4" flake complete coat to refusal. vacuum excess flakes.
4. sand flakes. vacuum.
5. clear coat.
6. sand. vacuum.
7. 2nd clear coat.
The work was done in 6 sections, each about 150sf, separated by the expansion joints. The joints weren't filled, but were coated. Each section was dry enough to walk by the time he got back around to it (about an hour). (Maybe used spike shoes -- I don't remember.) There was no odor. ALl the work was done in about 7 hours. It was dry enough to walk on in an hour and contents were re-installed the next day.
All seemed well until about 2 years later when I noticed that some chunks were coming off under the garage door weatherstrips (sticking to the door when it went up). Upon closer inspection, I found that within about 2 ft of the garage door, there were numerous cracks and some efflorescence. Over time, more chips detached, both under the doors and further in, and there were many places that sounded "hollow" where the coating was obviously detached from the substrate. This is in California and dry in the summer. In the winter when it's wet/humid, I frequently see efflorescence in the exposed bare concrete. The "harvested" chips are about 30 mils thick (including the flakes), indicating the overall thickness of the coating. The concrete exposed when the flakes detach is clean and shows no residue from the coating at all.
Except within about 2 ft by the garage doors, the coating seems to be sticking and holding up well.
The contractor that originally installed it is out of business and their warranty excluded efflorescence anyway.
Question is what to do now? I don't think it could be effectively repaired to match, but I guess it could be removed (ground or shot blasted). But what could I do to prevent it from recurring?
If there is, in fact, high water vapor pressure, it seems like I need something that is vapor permeable, but that seems like it reduces the utility of the coating. It's not practical to replace the slab or do any sub slab work.
Would a rougher substrate help (more surface area for the base coat to stick to)? Or some primer/moisture barrier before the base coat? Is MMA an appropriate coating in a garage application? I see mostly "epoxy" (but "epoxy" seems to be used to refer to any 2-part coating system in consumer products without detailing the chemistry actually used, and MMA is a 2-part product.)
FWIW, I paid $4.25/sf back in 2008, which, upon further research, now seems "generous". I have one quote to replace it for $5/sf.
Thanks.