Epoxy vs Sealer

[dipan]

I have a somewhat unique garage situation. There is only one car bay and 9' door, but the space is effectively an interior space (full HVAC) otherwise. It's about 1700 square feet. The concrete was heavily reinforce with rebar every 12". It's 4" thick 3500PSI and has compacted gravel and plastic underneath.

The unique part mostly is that there are no control joints. There is some hairline cracking throughout (I understand concrete DOES crack normally).

So ...

I would like to not spend a whole lot of money but want a decent looking and performing floor. Will work on car(s) and do other hobby type stuff in there. No **** allowed in my garage

I was initially thinking of just sealing the floor with a good quality sealer. I like the look of raw concrete, but there may be some problems with this approach. There are some in-floor drains for which the floor was not properly sloped. The concrete guys are going to have to grind this down, presumably exposing aggregate. So if I sealed, I would see aggregate in some places and not in others. Also, the hairline cracks would be visible, which by itself is no big deal. I assume the sealer would prevent any functional issues at the hairline cracks, like gas or oil leaking into a crack and staining.

Then I started looking into epoxy. I was thinking of a good quality epoxy from one of the vendors participating in this forum with full coverage chips and a urethane topcoat. I would hate to go to all the trouble of this multistage process and then have yellow spots and staining. BMW M colors in the chips would look badass IMO... This approach would presumably completely hide the hairline cracks and I wouldn't have any problems unless a new one developed.

Looking for advice and opinions ...

Thanks ...

 

[LegacyIndustrial]

You have offered up two different systems, varying in performance, appearance and price.
You may need to make some decisions before advice can be given.

 

[dcs Inc]

You need to address the cracks before applying an epoxy system. Even if they haven't spread they are now a weakened area that will crack down the road if any stresses occur, often caused be temperature changes.

 

[dipan]

You have offered up two different systems, varying in performance, appearance and price.
You may need to make some decisions before advice can be given.

Performance ... I assume the epoxy would be more durable and resistant to staining?

Appearance ... Epoxy wins for me but a slight sheen on raw concrete isn't too bad.

Price ... For the square footage I don't mind springing for a premium epoxy system. Paying a pro to do it would be too much though.

 

[dipan]

You need to address the cracks before applying an epoxy system. Even if they haven't spread they are now a weakened area that will crack down the road if any stresses occur, often caused be temperature changes.

Why? They are hairline cracks and not structural. I worry that if I fill them then epoxy I would just get cracking somewhere else. Temps should stay reasonably constant. I will set HVAC to heat to around 70 and cool to around 80.

 

[LegacyIndustrial]

Indy is correct, any cracks left unfilled will telegraph through the coating. Yes, even through a flake floor.

 

[LegacyIndustrial]

A full chip with all the goodies will have you near 2.5 - 3.00 psqft
acrylic coating (good one) will have you around .25 psqft
clear epoxy/urethane system is approx. 1.00 psqft.

These are materials and shipping.

Here is a link to a recent post from a gjmember using our HD6600 sealer, pics to see.

http://garagejournal.com/forum/showthread.php?t=206612

 

[dcs Inc]

Ah, always the salesman. Anyway, concrete placed on a really good compacted subgrade and kept at a constant temperature will never crack.... well, except for impact fractures. Concrete expands and contracts with varying temps. Having a weakened area (Hairline fracture....shrink crack) invites an expanding/contracting concrete slab to crack along this area. Concrete will crack along the weakest point.

 

[dipan]

Ah, always the salesman. Anyway, concrete placed on a really good compacted subgrade and kept at a constant temperature will never crack.... well, except for impact fractures. Concrete expands and contracts with varying temps. Having a weakened area (Hairline fracture....shrink crack) invites an expanding/contracting concrete slab to crack along this area. Concrete will crack along the weakest point.

He is of course one of the guys I am considering buying from ...

So the slab has been set up for a year now and in the next few months the HVAC will be fired up and the garage door won't be open all day for construction. It has been exposed to the temperature swings of south Texas for that time and presumably this led to the cracks. Again, the cracks themselves don't bother me, but I don't want the epoxy cracking if I do go that route.

My main concern is if I fill the cracks, since I have no control joints in a 1700 square foot slab, won't it just find another place to crack? I suppose that once the temps are relatively stable in the garage after construction is done is probably the best time to put the epoxy down.

 

[dcs Inc]

They install the control joints at placement to contend with the shrinkage. It's going crack so why not control the random cracks. Since this wasn't done on your placement the goal is to "recontrol" the cracks. Carefully fill the existing cracks with a really good epoxy crack filler and then recut new control joints. Make the new cuts deep so there's no doubt where the "new" cracks need to go. Since this has hydrated, no more shrinkage will occur so that is not a problem. The only thing now you need to worry about besides impact fractures and a weak subgrade is expansion and contraction due to changes in the temps.

 

[dipan]

They install the control joints at placement to contend with the shrinkage. It's going crack so why not control the random cracks. Since this wasn't done on your placement the goal is to "recontrol" the cracks. Carefully fill the existing cracks with a really good epoxy crack filler and then recut new control joints. Make the new cuts deep so there's no doubt where the "new" cracks need to go. Since this has hydrated, no more shrinkage will occur so that is not a problem. The only thing now you need to worry about besides impact fractures and a weak subgrade is expansion and contraction due to changes in the temps.

I understand the control joint concept, but not sure why I would have to cut new control joints now that the shrinkage has occurred? Don't people go to great trouble to fill the control joints with epoxy crack filler before epoxying the floor? In an ideal world I would like to have no seams (control joints).

If I end up going sealer or epoxy ultimately, I will try to fill the hairline cracks. There are thin two part polyurethane and epoxy crack fillers on the market (lots of examples on youtube) that would do the trick. They use silica as a filler it seems. The cracks are very thin, (pics would probably help) probably 1/32" or so, randomly distributed.

I'll try to take a pic as an example.

Thanks for all the help guys! I don't want to go through the time and expense of a DIY finish if the result is not awesome

 

[pauls_workshop]

Filling or not filling expansion or control cuts has been covered at length in the forums. Do some searches on it. There are two camps, those who fill in and those who don't. I would not fill any expansion or control cuts because if you do, epoxy on top can crack later on when they want to move on you later and re-crack there. If you don't mind the risk of that crack above later, then go ahead and fill with an appropriate flexible material in them. Most installers would not warranty no cracks above them if you fill them in. I would leave them be and epoxy up to the cut/joint on either side and leave those alone or if you want something there to have a flat floor without any interruptions, then I would fill in with something like SikaFlex poly caulk *after* you are otherwise done with the floor, which can look just fine and not have any cracking issues then.

Now, hairline or other cracks elsewhere on the floor, those I *would* fill in and grind smooth before epoxy on top because otherwise, that won't look good and they would telegraph though. For those, I would just use a 100% solids/white silica sand mix at 1:4 ratio and clean out crack first/fill/grind over flat.

- Paul

 

[moose75]

Hi there, I just finished the construction of my garage. I have yet to build shelves, workbenches, etc. but I did get the concrete floor sealed. I was told that I would be able to wipe up fluid spills easily and without any staining. The concrete is now stained from oil, and trans fluid spills that have stained the concrete thru the sealer. The product rep is supposed to come over to test the floor, since the concrete contractor has already seen it and said that, "That's not supposed to happen, and I have done hundreds of these floors and none of them have done this." Even if the floor is resealed and works correctly some day, I will forever have stains in the concrete that should have been avoided.
I would advise anyone that gets a sealed concrete floor to test a small area in a non-visible part of the floor to make sure that the sealer is working as its supposed to. On another note, my Father has had epoxy on his floors for over 20 years and it still looks great. I like the look of the concrete, that's why I wanted to seal it instead of using epoxy, but this *****. Be careful and good luck.