I need a clear coating for an existing concrete surface (less than 200 sf) that will be exposed in a commercial kitchen environment.
Have advised of other solutions (like a stainless steel wainscot, but the designer wants to see the concrete.
Concrete is a porous material. We’ve specified clear silane/siloxane water repellants for exterior use, but I’d be antsy about them making the concrete fully non-absorbent.
That’s an issue in commercial kitchens. I’d check with your health department to see if exposed concrete in such an environment is acceptable. That trumps what the designer “wants to see”.
Dave, good suggestion on the regs. Not so sure why you’re antsy on the concrete becoming non-absorbant?
I am also looking at sealers/coatings for concrete, but in an entirely different location, so not applicable for Peter. One thing I did consider was whether there was an issue with the concrete being unable to cure on the surface with the sealer. My SE claimed it was a non-issue as the other side of the slab was not being treated.
You can always raise questions like this with your SE on the team – I certainly do & they don’t mind at all 
Trapping the moisture in the concrete does not cause a curing problem. There is more than enough moisture in the concrete when placed for curing to take place. This would aid in the curing and reduce shrinkage.
If the moisture did not leave the concrete there would be no problem. Curing is not about extracting water from concrete. Just think of all of that concrete under water.
Differences in vapor pressure and resulting moisture flow can possibly cause sealar to pop off but with the right coating material that should not be a problem.
I expect you would want to fill in the rough surface so the surface can be kept clean and to prevent discolloration.
Karen, I’m antsy that the sealers would not make the concrete fully non-absorbent, ie that it would still have some surface absorbency/porosity. That’s especially important in kitchens because of the oil and grease.
I specifically asked for a “coating,” not a “sealer.” Because this is a commercial kitchen (albiet a small one-think the deli in your building), the wall finishes need to be “sanitary” and scrubbable to keep them that way. The building is more than 60 years old so I am not really worried about the concrete curing. The surface area in the kitchen is a very small part of the exterior wall (this is a 5-story building).
An ideal coating would be a white epoxy or latex-modified epoxy (water-borne epoxy), but the designer wants to see the concrete. Probably need either an epoxy or a polyurethane formulated to go over concrete.
They have already had preliminary conversations with the health department about “sealing the concrete”, but I have the sneaking suspicion that what we would consider a sealer will not be acceptable.
Dave - correct. I assume you’re talking about penetrating sealers and not film-formers.
Peter, there’s almost no way to avoid involving the health department - and that’s a bit of a crapshoot, as I’ve had different answers from different inspectors in the same jurisdiction.
But I can just about guarantee they’ll want to see some kind of clear film-forming coating in the kitchen. Check with whoever you use for fluid-applied floor coatings - they usually have vertical grade products for this type of application (specifically concrete floors and 4’ or so up the walls in restaurant kitchens). They may also be aware of the health department’s requirements in the project location.
The problem may preparation, though. Most clear, moisture resistant direct-to-concrete coatings that will have enough film build to satisfy a health inspector are high-solids epoxies, and normally preparation involves abrasive blasting (which will be expensive for 200 sq. ft.), acid etching, grinding, heavy wire-wheel abrasion etc.
None of them are very attractive (and etching is not really suitable for vertical surfaces).
The problem is most epoxies (and other heavy-duty concrete coatings) require a surface profile, and the methods for achieving the necessary profile are not normally used for clear coatings if aesthetics are a concern.
These clear coatings are used quite often in industrial corridors, mechanical rooms, etc. - but not because someone wants to see the concrete. The normal reasons are easy maintenance and low cost - plus they don’t look grungy as quickly as pigmented concrete coatings.
I’m sure you’ll be able to locate a product that can be used, but I’m not sure the client will like the look or cost.
Peter - have you checked with the manufacturers’ reps for paint/coatings you normally specify? As I mentioned, suppliers of fluid-applied floor coatings usually have vertical grade clear products as well.
But - please see the cautions noted in my previous post. Normal concrete preparation does not provide Architecturally-attractive surfaces for clear-coating and the client might want to re-think this one.
How about Formica Solid Surfacing, 603- Natural Concrete?
OK, I admit to being frequently gullible and too willing to believe what I find on the internet, but I looked up “Formica Solid Surfacing, 603- Natural Concrete” fully expecting a Friday morning Regener long distance leg pull. It’s a real product.
Will a methyl methacrylate product work?
David - I don’t see why not, but again the preparation might not provide the results the owner wants to see. Really, most any clear floor coating that can also be applied to vertical surfaces will work - but it’s a question of appearance.
Have you looked at Tnemec Series 201 Epoxoprime? It’s a clear, waterborne, 100 percent solids epoxy. Of course this type of product does tend to yellow over time. Tnemec requires that everything get blasted prior to application of their products so maybe the designer won’t be happy with the look afterwards anyway.