TIL that a wet spot on a garage floor can ruin a whole day's work if you don't catch it early

I was doing a garage floor in Phoenix last June, about a 500 square foot pour, and everything looked perfect. But about halfway through the finish, I noticed a dark patch near the edge where the slab was still wet. Turns out the ground underneath had a low spot that held water from the night before, and it wicked up through the concrete. I had to stop, wait for it to dry out, and then patch that section after it cured. It left a visible color difference in the final slab, and the homeowner noticed right away. Has anyone else dealt with moisture coming up from below like that?

2 comments

2 Comments

pat_murray1628d ago

Did you see that article in Concrete Construction magazine a few months back about capillary breaks? They were saying even with a vapor barrier, if you don't put a layer of washed gravel or a drainage mat underneath, moisture can still wick around the edges somehow. I mean idk if that's what happened here, but it stuck with me because I'd never thought about the sides of the slab being a problem.

sam_anderson28d ago

Put a vapor barrier under the slab next time. Six mil poly sheet, overlapped and taped at the seams, stops that wicking dead.