Epoxy over paint?
- Thread starter 66pnl
- Start date
AlphaGarage
Well-known member
If the existing paint is still sticking well to the concrete, and if you use a quality epoxy primer, there's a good chance that it will not fail. However I doubt any company would guaranty that application. Your best avenue would be to remove the current paint.
There are 3 common ways to remove old coatings...
STRIPPING / SCRAPING:
A stripper solution can be applied to previously coated concrete surfaces, and the old coatings may be scraped off using a paint scraper. Depending on the properties of previous coatings, and the striping product being used, numerous stripper applications may be required. The stripper and scraper alone may not adequately remove certain coatings, in which case mechanical methods, like grinding or shot blasting, might be better options.
GRINDING / SURFACING:
Grinding may be used to remove existing coatings, and level out high spots. This method uses horizontal rotating disk(s) to leave a smooth surface texture; so smooth you may need to rough it up a bit with high pressure water or a chemical etch. For the Do-It-Yourselfer this might be the best method.
Grinders are available for rent at many “big box” stores and construction equipment rental yards. A good model to look for is the EDCO disc grinder with their Dyma-Serts (avoid “stones,” they usually aren't aggressive enough). See equipment supplier for applications, use instructions, and precautions.
SHOT BLASTING:
Shot blasting removes thin coatings, cleans the concrete surface, and gives your floor a rough profile. A degreaser may be necessary prior to shot-blasting if floor has an accumulation of grease and oil. Shot blasting can be aggressive and care must be taken to not over blast. Equipment can be hard to find, prices vary widely and are generally costlier than floor grinders.
As with any piece of gear you're unfamiliar with, try it out in an inconspicuous area first. These aren't that complicated, with a short learning curve, but a common novice mistake is over blasting or over grinding. Not a fatal mistakes, ones that can be overcome with using a bit more epoxy coating... on 2nd thought, don't practice first
A quick note about leaving the current coating - Although it may be holding up fine now, coating over the existing material could accelerate its failure. That's because depending on its composition it may be allowing the transmission of water vapor, or hydrostatic pressure. However once coated with a non-permeable epoxy that pressure could prompt the release of the old coating. Considering the cost and resources required to put down a new floor coating system, the old stuff really should be removed first.
There are 3 common ways to remove old coatings...
STRIPPING / SCRAPING:
A stripper solution can be applied to previously coated concrete surfaces, and the old coatings may be scraped off using a paint scraper. Depending on the properties of previous coatings, and the striping product being used, numerous stripper applications may be required. The stripper and scraper alone may not adequately remove certain coatings, in which case mechanical methods, like grinding or shot blasting, might be better options.
GRINDING / SURFACING:
Grinding may be used to remove existing coatings, and level out high spots. This method uses horizontal rotating disk(s) to leave a smooth surface texture; so smooth you may need to rough it up a bit with high pressure water or a chemical etch. For the Do-It-Yourselfer this might be the best method.
Grinders are available for rent at many “big box” stores and construction equipment rental yards. A good model to look for is the EDCO disc grinder with their Dyma-Serts (avoid “stones,” they usually aren't aggressive enough). See equipment supplier for applications, use instructions, and precautions.
SHOT BLASTING:
Shot blasting removes thin coatings, cleans the concrete surface, and gives your floor a rough profile. A degreaser may be necessary prior to shot-blasting if floor has an accumulation of grease and oil. Shot blasting can be aggressive and care must be taken to not over blast. Equipment can be hard to find, prices vary widely and are generally costlier than floor grinders.
As with any piece of gear you're unfamiliar with, try it out in an inconspicuous area first. These aren't that complicated, with a short learning curve, but a common novice mistake is over blasting or over grinding. Not a fatal mistakes, ones that can be overcome with using a bit more epoxy coating... on 2nd thought, don't practice first
A quick note about leaving the current coating - Although it may be holding up fine now, coating over the existing material could accelerate its failure. That's because depending on its composition it may be allowing the transmission of water vapor, or hydrostatic pressure. However once coated with a non-permeable epoxy that pressure could prompt the release of the old coating. Considering the cost and resources required to put down a new floor coating system, the old stuff really should be removed first.
Last edited:
Hammerdown
Well-known member
AG- Man you always got it covered with thorough answers. I'll chime in if you don't mind and say for removal grinding would be the way most DIY'ers can get good results without screwing up too bad! Rent an Edco grinder with the Dyma-Sert tips and remove the existing paint back down to the concrete. Having a fresh "canvas" for your project is always the best and will help ensure the coating system you choose will have the best chance of success. If you want to go over the existing coating you should sand it with an aggressive grit, like a 60 to scarify the surface of the coating and create some texture for the new coating to adhere to. It would be dependant on that first coating for its adhesion to the concrete, so it is always a risk going over another product.
