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jf07120 05-29-2009 06:38 AM

Painting a Concete Garage Floor
I have a garage flor that has been painted with a poor paint or the individual did not seal it because it's peeling off. There is also some cracking and pits in some places.

what steps do I need to take to fix this and ultimately paint it again?

Nestor_Kelebay 05-30-2009 02:14 AM

The peeling MIGHT be because a poor paint was used. But, it's also very possible that the reason why the paint is peeling off is because moisture is evaporating from that concrete garage floor.

Water underneath the concrete garage slab can wick up and migrate upward through that concrete. When it reaches the top surface of the concrete, it wants to evaporate, but any paint on the surface of the concrete may prevent that from happening. Water is stubborn. It will both expand when it freezes or expand when it evaporates with tremendous force, and that force will push any impermeable paint off any substrate, including epoxy paint off of a concrete garage floor.

If it wuz me, what I'd do is get a piece of clear plastic sheeting (like vapour barrier) and tape that clear plastic down (around it's perimeter) on the worst area for peeling on your entire garage floor. Do that first thing in the spring when the snow starts to melt, and put a "hygrometer" under the plastic before fully taping down it's perimeter. A hygrometer measures relative humidity, and any increase in humidity under the plastic means that moisture is evaporating out of the concrete slab at that location. And, that means that ANY impermeable coating (like epoxy paint) that you put over the concrete at that locations will peel off. There's no if's, and's or but's about it, if you put an impermeable coating over any place on that slab that moisture evaporates from, then that coating isn't gonna last. It'll crack and peel at those spots.

You can buy relatively cheap hygrometers at Lee Valley or any place that sells hobbyists supplies.

You should be able to do the same thing after a heavy rain. What's needed is for the ground water level to be so high as to get the bottom of the concrete slab wet. When that happens, the concrete will absorb moisture, and some of it will migrate to the top of the slab where it will register as an increasing relative humidity under your plastic.

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