Concrete drying (water) before epoxy...

[BigDawg]

I know the title sounds kind of odd, but here is my dilemma. I have perfect weather this week and I etched the floor two days ago. The floor is seemingly dry and I REALLY want to epoxy today, but after nytehawk's thread, I am wondering if I should wait a week just to make sure everything is bone dry before epoxying. I am using the water based EpoxyShield.

Any suggestions? How long has everyone else waited?

 

[v8garage]

Is this a new slab? If not I don't understand the question. If it is a new slab you are supposed to let the concrete cure for six months before applying epoxy.

 

[BigDawg]

No, this is a four year old slab. The question is the amount of time for it to dry after etching and using water. Basically I don't want to apply epoxy if it is going to come up later because of trapped vapor due to me not waiting long enough.

 

[boiler7904]

Tape a piece of plastic down in a couple of spots for 24 hours. If the area under the plastic is darker than the uncovered area when you remove it, the slab is still drying and needs to sit longer.

 

[AlphaGarage]

It really depends on what the manufacturer specs. Some epoxies are far more tolerant of surface moisture than others.

Also, the standard minimum time required between a pour and first coating is 28 days. But again, check the specs.

 

[nytehawk]

Living here in the high desert, I just let my floor dry overnight (with an oscillating floor fan left on low for air circulation) before applying the epoxy. Other than the finger rub test in the instructions for dust and dryness, I didn't do any sort of test to verify the concrete was dry. I probably should have done a test with piece of plastic as recommended above, but since I was doing this in late July I was much more concerned about temperature than moisture.

Edit: also, I guess since I was using the water-based EpoxyShield I wasn't concerned with making sure every last molecule of moisture had evaporated from the floor. However, it wouldn't surprise me if the solvent-based and water-based epoxies have very different levels of tolerance for moisture in the concrete during application.

 

[Andy S]

Ya a water based epoxy.... two days dry time should be no problem. Its going to allow vapor transfer anyways, until you put your next coat on it. I have a moisture tester, but i guess going to spend 300$ on one isnt worth it.

 

[BigDawg]

Ya a water based epoxy.... two days dry time should be no problem. Its going to allow vapor transfer anyways, until you put your next coat on it. I have a moisture tester, but i guess going to spend 300$ on one isnt worth it.

You said this...which raises another question. Is it possible to apply water-based epoxy on top of itself once it is cured? Is that just overkill?

 

[Andy S]

Well your going to need a second coat of epoxy anyways. You could go for a water based again if you wanted, or a solvent based. Whichever you find easier to apply. I dont really use epoxies that much any more, someone else will be able to tell you what you should use. But you could def use another coat of water based without a problem. Do you want a breathable floor or not?

 

[Mlynch]

when recoating epoxy... or any coating you need to follow the rules. There will be a time frame in which you have to recoat it. If you miss this time fram and wait too long you need to generally lightly sand and solvent wipe the epoxy. I dont use water based products but i beleive this rule is universal.

 

[BigDawg]

I saw no information in the instructions regarding a second coat. Oh well. If it starts to mess up at all, I will do the sanding and solvent wipe and then apply another coat.

 

[Andy S]

Well water based epoxies are generally used as a primer. What epoxy are you using? Ya like Mlynch said, if ya miss the window, it wont bond. I beleive the rule is 24 hours.... i would coat it as soon as you can.

 

[Mlynch]

yeah most 100 percent solid epoxies are 12 - 24 hours... not sure about yours water based stuff.

 

[T-Ricky]

I Just applied Quikrete 4 days ago. Looks like @$#@ with alot of overlap marks. Called company and they suggest recoat using 3/8 foam roller. Looking for all suggestions to keep this from reoccuring.

 

[AlphaGarage]

T-Rick - How thick is the coating you put down? If it goes on real thin you have a smaller margin for error. Thin spots will look thin, and overlaps will be noticeably different. Just like latex wall paint, if too thin it looks bad.. A difference, one that works in your favor, is that with a floor epoxy your next coats can be put on thick.

So for your next coat try putting down more material - it should cover the flaws and level out. If it's a good epoxy you can put down a thick coat without having any issues, 12 - 20 mils.

I'm not a big fan of the foam rollers.

 

[T-Ricky]

Sounds like I may have been to thin. Only used 1 1/2 cans for a 506sqft garage. Will sanding help and should I be worried about tire pickup with second coat. Floor was etched twice before first coat.

 

[AlphaGarage]

Unless there's a huge disparity of coat depth I wouldn't sand. But it's tough to say without running fingers across the surface.

Just make the next coat thick enough and it should work out.

 

[T-Ricky]

Thanks for the info. Also do you think a clear coat might help after the second coat or will this show the heavy spots more!!

 

[Mlynch]

yes that is pretty thin... you have to sand or solvent wipe if it has been 4 days you are outside of the recoat window. In this case the sanding is for adhesion rather than fixing your messups.

12- 20 mils is nuts for that kind of epoxy you will have problems... check your other thread and read your quikcrete directions