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-   -   Epoxy over Latex??? (http://www.houserepairtalk.com/f107/epoxy-over-latex-9682/)

bbray1012 08-02-2010 06:25 PM

Epoxy over Latex???
 
Hello! I would like to re-paint my front porch (concrete) that was previously painted with several layers of what looks like latex paint. I bought the house a month ago and the paint on the porch is worn to the concrete in some areas, while it is peeling away in others, and in good shape in other areas. If I remove all of the loose paint the best I can, is it possible to put epoxy over the top of everything to try and cover alot of imperfections within the concrete (small cracks, divets, and bumps)? I'd like to continue all the way around the foundation if it is possible, or feasible. Would I be better off just going over it again with latex? If I get 5 years out of it before repainting I'd be happy!!

Nestor_Kelebay 08-04-2010 09:59 AM

It's never a good idea to put a hard strong coating over a soft weak one. The reason why is that the soft weak coating will be the weakest link in the chain, and any impacts to the porch will result in the latex paint breaking, with the result that the epoxy paint will get all "chipped up" as a result.

To remove the paint you have, I would paint it with a methylene cloride based paint stripper like Polystrippa and then cover over what you've painted with plastic bags split open. Sticking the plastic bags to the paint stripper will prevent the paint stripper from drying out, allowing a much longer working time for greater penetration into the paint and therefore easier removal of it. Maybe use acetone or lacquer thinner to remove any printing ink from the plastic before using the bag since that ink might dissolve in the paint stripper and stain your concrete.

If you do paint over your front step with an epoxy paint, be aware that those steps are gonna be slippery when wet or covered with snow, and that's going to make you a law suit magnet for anyone who needs some extra cash before Christmas. You'd be much better off to glue (or otherwise install) an indoor/outdoor carpeting on your front steps which won't ever be slippery.

I'd be reluctant to paint your foundation from the outside. First off, there's negligible moisture getting into your foundation above the ground level. Most of the moisture getting into your foundation will be below ground level, and so if you're trying to reduce humidity and mildew growth on the walls in your basement, you really need to waterproof the entire outside of the foundation, not just the top foot or so. Secondly, painting the exterior of the foundation is going to prevent moisture in that concrete from evaporating out. The concern here is that as the moisture in the concrete accumulates, you could have freezing of that moisture and the resulting expansion of the water as it freezes could cause spalling damage to the concrete. Spalling is where the surface of the concrete breaks off in "flakes" or "chips", and is due to water in the concrete expanding as it freezes. So, unless you have a good reason to paint that concrete, you'd be best off leaving it bare so that moisture can evaporate out of it.

Cold concrete is happy concrete. Wet concrete is happy concrete. Concrete only gets mad when it gets wet inside and then freezes. Then you get spalling damage. So, if it ain't broken, don't fix it.

bbray1012 08-04-2010 07:02 PM

Thanks for your reply. Unfortunately, the foundation walls were already painted a battleship gray and I was just looking to upgrade the appearance. The porch and steps are gray as well, but are in poor shape paint-wise. Would a latex paint be a better choice for the porch, after I stripped it the best I could?? Just looking to get a couple of years out of it before I cover over it all with decking.

Nestor_Kelebay 08-05-2010 12:03 AM

No, latex paints form softer films than oil based paints and they're really not hard enough to provide good service on a working surface like a floor. My own experience with using a latex "Porch and Floor Enamel" over a concrete locker room floor was dismal, and I ended up stripping off the latex paint and using an alkyd based polyurethane (which still looks like new).

But, even a latex paint would give you a few years if that's all you're after.

Use a latex "Porch and Floor Enamel". These kinds of latex paints will use something called a "cross linking acrylic polymer". It forms a film just like a normal paint, but then it also crosslinks over the next month or so, making the paint harder and stronger, which is what you need to stand up well on a working surface like a floor. And, if I were you, I'd use a traction grit in the paint to keep it from being slippery when wet.

If you do paint your foundation, use a latex MASONARY paint. Masonary paints are always latex paints because latex paints have the ability to "breathe", which means that they can allow individual H2O molecules to pass through them, but not liquid water. If you imagine an acrylic plastic resin as a long wire scrunched up into a ball, then there will be spaces between the wire within each ball. Those spaces are larger than the diameter of a single H2O molecule, but smaller than the distance between H2O molecules in water. So, individual H2O molecules can pass through a masonary paint quite easily, but not liquid water. In fact, masonary paints are chosen according to the plastic binder resin's permeability to H2O molecules. Anyone making a masonary paint will be wanting to use a binder resin that allows individual H2O molecule to pass through it with ease, but which won't allow any liquid water to pass through it. ALL latex paints will do this to some degree, but masonary paint will do it the best.

The result is that a masonary paint acts much like a check valve in that it will allow moisture that does get into the masonary wall to evaporate out through the paint, but that same paint won't allow rain or snow melt water to get into the masonary. So, if the person that painted that foundation knew what they were doing, they would have used a masonary paint, and you won't do any harm by painting over a masonary paint with another masonary paint. But, if what you have now isn't a masonary paint, then painting over it with a masonary paint won't do any good. (It won't do any harm, but it won't do any good since the existing paint is going to limit the amount of evaporation that can take place through the combined paint films.)

Don't use the same paint for both porch and foundation. On the porch you want as hard and strong a paint you can get, and on the foundation you want a paint that will allow individual H2O molecules to pass through it easily. You're not likely to find one paint that will do both those jobs well.

Also, you're not likely to find an EXTERIOR Porch & Floor Enamel. Just use a Porch & Floor Enamel intended for interior floors. That's cuz the only difference between interior and exterior latex paints is the additives like UV blockers and fungicides added to exterior latex paints. But, the area you're dealing with is small, so it's not a big deal if you have to spray down the porch with a 10% bleach solution to kill any mold growing on it, or repaint in a few years because it's deteriorating from UV exposure.

ZoneIII 09-17-2012 07:41 AM

The responses here are examples of why you have to take everything you read in forums like this with a grain of salt. The first response is riddled with errors. It recommends that you use garbage bags to cover paint remover to allow it to work longer. Why would you use garbage bags? Why not plastic sheeting? And forget about using lacquer thinner, etc., to remove ink on the bag. Those chemicals will dissolve the plastic and make for a real mess. And don't worry about ink because you won't be using garbage bags anyway and, even if you did, the letter ink would not stain your concrete and even if it did, you are going to paint it anyway.

The second response was much better and had some good information but, oddly, the person who wrote it first said he had a "dismal" experience when he used latex Porch and Floor Enamel and then he goes on to recommend that you use latex "Porch and Floor Enamel (???).

If the areas is small, a good alternative would be to remove as much of the existing paint as possible either mechanically (sanding) or chemically. Then clean the floor thoroughly and etch it with muriatic acid and rinse thoroughly. When dry, use two-part epoxy pain with traction material added. Then sell the traction material where they sell two-part epoxy paint. Don't used products called "concrete stains" or "latex epoxy", both of which are just paint. Believe me, you will regret it if you use either of those products. You need a good, tough coating.

chaddlyndon 09-22-2012 08:06 AM

All incorrect answers. I work in a paint store and have for the last decade. All epoxies yellow and fade outside, no exceptions. For exterior floor coatings like you're doing your best bet on concrete will be H & C Solid Color concrete stain. Rent a floor grinder and abrade the entire surface. If it comes down to bare concrete use the Xylene or solvent based version, if there is still old product left use the latex version. The Xylene version will lift previous coatings. It last numerous years on driveways against vehicle traffic, hot tire pick up, and salt from the winter. This will easily do the job on your front porch which is just going to be foot traffic. Solid Color Concrete stain is NOT a paint. It looks like paint but it penetrates and soaks into your concrete and that's why it's one of the better products out there


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