One question that is often asked is how to apply a new coat of epoxy or clear coat to an older epoxy floor that has already cured. If you’ve done a little bit of research on epoxy application, then you know how important floor preparation is. So let’s discuss how to determine if your floor qualifies for a recoat and then how to prep the floor before you do.
When can you apply epoxy over an older coating?
There are many examples of when you can apply a new coat of epoxy over an older coating. The most common of these reasons are for people who had previously applied a color coat and now realize that they want the glossy looks and advantages of adding a clear coat.
Sometimes it’s as simple as someone who planned a multiple coat flooring system and waited too long between coats, allowing the epoxy to cure, before applying the next coat in order to get a chemical bond.
Another reason is to renew the clear top coat. After many years of service in a busy garage, the clear top coat of an epoxy floor can start to show its age. With the proper floor preparation, you can add another coat of clear and make the floor look brand new again.
And then finally, you may have an older existing coating that is showing wear from years of heavy traffic and getting thin. As long as the floor is not experiencing any delamination issues, many times you can recoat right over a worn epoxy floor to create a brand new looking finish.
As long as the existing garage floor coating is a 2-part resinous product such as epoxy, polyurea, polyaspartic, or polyurethane, then you should be able to apply an additional coat of a compatible product without issue. However, to be safe you should always consult with the manufacturer of the new coating first.
When not to apply epoxy over an older coat
If the existing epoxy floor coating is peeling up or showing other signs of delamination, then you do not want to epoxy over it. There are bigger issues at play here that are causing the delamination. Applying a new coat of epoxy over such a coating will only lead to more problems. A complete removal of the old coating by grinding would be required.
If the coating is fairly worn with more concrete showing through than there is epoxy, then you will want to start fresh by grinding the floor.
Do not attempt to apply epoxy over existing concrete sealers. These need to be removed first as epoxy will not adhere to them. Also, floor paint is not a good base for epoxy and needs to be removed as well.
How to prep epoxy for another coat
The key to applying a new coat is to mechanically rough up the surface of the older coat to create enough bite for the epoxy to adhere to it. There are a couple of ways to achieve this.
The first is to use 150 grit sandpaper on an orbital sander or pole sander
Once done, sweep up the heavy stuff and then vacuum the entire floor with a shop vac. Next, use denatured alcohol on a small towel and wipe down the entire surface. The denatured alcohol will remove all the fine dust particles, evaporate quickly, and make sure that the surface is clean.
The other option is to use a floor maintainer (buffer) with a 100 grit sanding screen. You can usually rent these fairly inexpensively from your local home improvement center. They should have the sanding screens to purchase as well.
This method will go faster than the pole sander and cover a lot of floor quickly if you have quite a bit of square feet to prep. Just remember to occasionally check the sanding screen for wear and to make sure it hasn’t clogged up. After you are done, vacuum the floor and use denatured alcohol as described with the sanding method.
If you have an older clear coat that you want to renew, then you will want to use 80 – 100 grit sandpaper or a 60 – 80 grit sanding screen first to actually remove a small layer of the coating. This will help to eliminate any deeper scratches and/or embedded dirt that has marred the finish.
Do the same if you have a worn coating that is adhered very well but has some spots where the coating has worn through to the concrete. The more aggressive grit will insure that the bare concrete will be prepped properly as well.
Floor prep such as this goes fairly quickly. Once you wipe down the floor with the denatured alcohol, your floor is ready for a new coat of epoxy or floor coating of your choice.
Is rock solid a 2 part expoxy like reg expoxy kits Ben
Hi Ben. Yes, it’s very similar. We have an article here about RockSolid that is very informative.
I have a previous epoxy installation which was the victim of out-gassing, MVT (Moisture Vapor transmission), or blisters. Bubbles did form during the drying process and now there seems to be a foul smelling liquid oozing through where the bubbles formed. How do I repair this? The epoxy was a 100% solids from Lowes. This is an older concrete and not a new pour. The concrete was etched and dried for 48hrs prior to epoxy application. A vapor test was done with no evidence of moisture.
Hello Kevin. The foul smelling liquid is generally and indicator of mineral rich water coming from within the concrete. Since you mentioned that it passed a moisture test, it would then be an indication that the floor was not allowed to dry fully before the epoxy was applied. Concrete can take a while to fully dry out depending on how much water was introduced. Humidity is a factor as well. If it was more humid it will take longer for the concrete to dry fully. If no epoxy primer coat is used, it’s also best to apply 100% solids epoxy when the outside temperatures are decreasing. If it’s applied while the temps are increasing, any moisture still trapped in the concrete (including air) will rise to the surface and get trapped in the coating thus forming bubbles.
The good news is that a new coating will fix the issue providing that it was not caused from moisture issues within the slab to begin with (hence the moisture test). For bubbles, it’s best to sand the surface to smooth them out and prep the surface at the same time. A floor maintainer with a 60 grit sanding screen works best and is fastest. A pole sander with 80 grit sandpaper will do the job as well, it will just take longer.
Thanks for the feedback. After sanding and cleaning the area should I use a primer over the entire surface and then re-apply the 100% solids epoxy? Since the floor was sealed with epoxy, it seems the liquid is still coming through the pinholes/craters (applied about 1 month ago) Also, this concrete is in a basement work shop. What are your thoughts?
If liquid is still oozing through the pinholes after a month, Kevin, it looks more than likely that your problem is a true moisture issue and not an issue with not allowing the concrete to fully dry before application of the epoxy – particularly since we learned it is in a basement. This can open a whole new can of worms unfortunately. Applying a new coating may result in the same issue from the same pin holes. You could apply a special epoxy moisture vapor primer and then a coat of color epoxy over that, but the original epoxy may eventually delaminate from moisture beneath it. The only way to tackle the issue and know that it will work correctly, would be to grind the epoxy off and do a calcium chloride test. If the moisture is not too high you can apply a moisture vapor barrier epoxy primer and then a coat of color epoxy.
Is there a particular primer you would recommend?
Legacy Industrial has both the standard epoxy primer and the moisture vapor barrier primer, Kevin. We would suggest giving them a call and tell them about your issue.
Hi. Can rocksolid be over epoxy? thanks ben
Yes. As long as you properly prep the old coating, you can apply RockSolid over it.
Hi can I wash down garage floor and rinse off instead of using denatural alcohol after getting it rugged up b thanks ben
You can, Ben, but it introduces water into the picture which you do not want coming in contact with a new coating. If no bare concrete is exposed, you will be OK as long as you make sure the floor is dry. If bare concrete is exposed you will need to wait a minimum of 24 hours for the concrete to release the moisture that it absorbed. What denatured alcohol does is save time and eliminate all dust. It evaporates quickly which enables you to recoat the floor immediately after it has been wiped down.
Just did the floor with RockSolid in grey. Looked great right after applying product, then about 30 mins later we started seeing “non shiny” patches which got larger and then there were many areas like this over the whole garage floor. I figured it was just curing and decided to wait till the next day to re-evaluate it again. Nothing changed and now it’s been 2 weeks and it really looks bad, some shiney areas, some dull area, some lighter areas and some darker areas. Yuck! I’ve done 2 other homes with the basic floor coverings and never had this problem. This is the first time using “RockSolid.” What do you suggest, can it be resealed/redone. It’s rather embarrassing to show family and friends our “new” garage floor now…
Hi Terri. Did you follow the coverage rates or did you try and stretch it a little? The biggest issue with RockSolid is that the coverage rates stated in the instructions are optimistic at best. If you tried to cover more of your floor than stated you will run into these issues. The “non shiny” areas you refer to are a matte finish that is produced when the coating is too thin. This happens if the coverage rate is stretched and/or the concrete has absorbed more of the coating than the surrounding areas. The biggest issue people have been having with RockSolid is just as you described. RockSolid is not a thick coating to begin with and it penetrates concrete very well. If you have areas that are more porous than others this can happen.
The good news is that it can be corrected with another coat. The first coat acts as the primer coat. The second coat actually goes on thicker and will be very glossy. None of the material will be lost from being absorbed by the concrete. Since you are past the 7 day recoat window, it will require that you rough up the surface with 120 grit sandpaper first in order for the new coat to adhere properly. Also, we recommend that you contact Rust-Oleum Customer Service and tell them of your problem. If you have not stretched the coverage rates, we’ve received many reports that Rust-Oleum has done a good job with helping customers out.
Do you use reg sand paper 150 grit after doing a foot or it seems like all the grit is all worn off
Hi Ben. If the sandpaper is being used on the coating you should not be wearing out the sandpaper that fast. The idea is to just degloss and add some roughness to the coating. You don’t need to sand through the coating. If you have some real rough areas of coating, you may want to drop down to a rougher grit such as 80-100 grit.
Bought 22 year old home…garage floor is blue/grey with flakes….it is very dull & worn, but no peeling. How do I know if the original coating was epoxy & what can I safely recitation it with?
Hi Susan. Pour 1/2 oz. of acetone in an inconspicuous area and let it sit for minute. Next, wipe it up vigorously with a rag. If the coating does not soften up or bleed heavily, then you have epoxy or an equivalent. If the coating has not worn thin, you can rough it up with 80-100 grit sandpaper to remove the upper most layer of dirt and debris and then recoat with a clear. This will bring much of the color back and give the coating some gloss. You will lose some flakes in the process.
I have a garage floor that had a 3 step epoxy coating applied with flakes (little stones) applied on the 3rd step. The floor is 3 years old. The floor is in good condition. Do I need to apply a clear coat over the floor now and if so, how do I do it? Thanks.
Is there a clear coat on it now, Dave? And what do you mean by little stones? Are you referring to an anti-slip grit?
I put down the water based rust-oleum epoxyshield about 16 years ago with a clear on top (and anti skid). It has held up very well with only a couple of spots worn through to bare concrete (granted it’s very dull looking now). I’m looking to repaint and apply the exact same product and clear. My question is for roughing up the surface, I started with a pole sander and 80 grit sandpaper, but how much pressure should I be applying? I know the surface should be dull after sanding but it’s already dull so it’s hard to tell if it’s doing anything (also, the anti skid makes it tough to tell as well because the surface is not smooth). One other question, where the epoxy has worn off to bare concrete I assume I’m ok just to paint over it? I did hit the whole garage floor with a pressure washer (electric) and very little extra paint chipped off (so it’s on there pretty good).
Hello Kevin. You should use moderate pressure when roughing up the surface. As long as you are producing some epoxy dust (it doesn’t take much) while you are sanding you will be fine. We suggest using the supplied concrete etch on the bare concrete areas to ensure that the new coat bonds well. Just make sure you allow those areas to dry thoroughly before application. Though you used a pressure washer for cleaning, we would also suggest that you take a scrapper to the edges were the epoxy has worn away to make sure there is not anymore loose material. As a last tip, wipe down the surface with denatured alcohol on a lint free cloth before you start the application process. This will remove the remaining fine dust and debris on the surface that sweeping and vacuuming will not get.
Would it be ok if I used the concrete etch on the epoxy area as well (in other words, will it hurt anything)?
The etch that comes with the kits will not do anything to the epoxy, Kevin, so it’s OK if it gets on the coating. Etching solutions (even acid) will not have much of an effect on coatings other than to possibly discolor or degloss them. Etching solutions only work on bare, unsealed concrete.
My husband applied one layer of the 2 part epoxy in our garage, put the flakes down and allowed it to dry before he realized that he should have put two coats of epoxy for it to be cover better as with ine coat it scratches easier. It’s been only one month since he did this and I want to know if it is safe to add a second coat on top of the current coat?
Hi Stephanie. You can always add more coats. It requires that the surface be deglossed and roughed up with 120 grit sandpaper first. Keep in mind that more coats will not make it more scratch resistant. The quality of the coating controls that. However, multiple coats will help the coating to last longer from wear and use. A good clear coat may be a better option for you unless there are areas where the coating is thin and the color is not good.
I built a concrete bar, I did the fake granite finish on the surface and applied that epoxy mix from Home Depot but I under measured and now the surface looks uneven :(. Can I apply another coat over the new epoxy??
Hello Patricia. Yes, you can apply another coat if you like. Rust-Oleum allows up to 76 hours to recoat without any additional prep. However, we would recommend sanding it with 100 grit sandpaper first to smooth it out if it seems uneven to you.