Best way to paint an old concrete floor?
Q: What is the best way to paint an old concrete floor?
A: This is hard to address in a short format so hopefully this is not too much information. I feel a responsibility to be overly thorough because floor painting can be very technical and if done wrong cause years (maybe even decades) of grief.
When painting floors you must consider location, surface type, surface condition, and if previously coated what that coating is.
Here is a breakdown of the types of floors commonly found in self-storage facilities.
Previously coated surface, regardless of substrate, with no failure. The easy one to refinish:
Prepare floor and recoat with a compatible coating.
If you are unsure what the existing is, do a test patch and check adhesion after 48 hours
Previously coated surface with some failure:
Determine why it failed; remove as needed any existing coating at risk of continuing to fail. Follow guidelines for repainting based upon the type and condition of surface it is.
Chose an appropriate coating and follow label instructions for surface prep, priming, etc. If it is delaminating plywood a hi-build primer will help even the surface out.
Raw, unsealed concrete:
Verify no "gassing" or moisture is present or will be occurring. Choose a coating, clean and prepare as directed on the label and finish as directed.
Sealed concrete, this is the precarious one:
Absolutely necessary to determine the type of sealer. If it is an acrylic type then you are home free, just choose a product, follow the instruction and apply.
If it is a silicone, siloxane, or non-drying oil type of clear sealer then you must remove it via shot blasting or diamond grinding. You cannot coat over these sealers with anything but what it was originally sealed with. If in doubt do a test patch to check for adhesion or forever have a peeling floor.
Common types of coatings (not including curing agents such as "Ashford") :
Silicone & siloxane sealers, clear only: Mostly for waterproofing, leaves no surface finish. Can only be used on unsealed raw concrete and can never be recoated with another type of product.
Acrylic "floor wax", Clear only: Same as used for janitorial application. Recoat every year or two. Subject to build-up and Yellows with time.
Concrete stain/sealer, clear and pigmented: Durable but can only be used on unsealed raw concrete.
Basic water based acrylic floor paint, clear and pigmented: fast dry time, Inexpensive but mars & stains easily. Plan on repainting every year or two to keep up. (Note, do not be fooled if labeled "epoxy fortified." If it is a single component it does not add much.
Basic oil based floor paint, pigmented only: Strong order, 24-36 hour dry time, flammability issues in confined spaces and not recommended for use on raw concrete. Not good for self-storage environments.
Two Component water based epoxy, clear and pigmented: Low order, fast dry, no solvent so no flammability issues in confined spaces. Very easy to apply and three times more durable than basic acrylic floor paint. Yellows outdoors.
Two component solvent based epoxy, clear and pigmented: Very durable however strong order, 24-36 hour dry time, flammability issues in confined spaces. Yellows outdoors.
100% solids epoxy clear and pigmented, the most durable option: Very high build, up to 1/8", Low order, no solvent so no flammability issues in confined spaces however it is more difficult to apply, 24-36 hour dry time and is expensive. Yellows outdoors.
Wash and clean: For recoating of existing painted floors only.
Sanding: For recoating of existing coatings, preparing raw wood for coating, some removal of failing paint.
Shot Basting: removal of old coatings and opening of 'pores' for new and old concrete. Leaves distinct, sometimes uneven surface texture.
Diamond grinding: removal of old coatings, opening of 'pores' of new and old concrete, smoothing out rough concrete. Leaves smooth surface but may leave some visible swirl marks when coated with a clear .
Acid Etching: opening of 'pores' of new and old concrete, cleaning of old concrete. Can only be done over raw, unsealed concrete. Requires full hi-pressure water blasting to clean after application. Not feasible for most self-storage applications
Notes on surface and environmental conditions:
Hydrostatic pressure, commonly known as moisture release or 'gassing': Mostly on grade or below grade concrete. Very difficult to solve, however must be solved prior to application of coatings. If present and causing paint failure shot blast or diamond grind to remove and get professional recommendations.
Efflorescence (white crystals on concrete): Sign of moisture issues, treat same as Hydrostatic pressure
Inter-coat adhesion issues: Remove via failure shot blast or diamond grind on concrete, sanding on wood then apply compatible coating.
Oil/Grease surface contamination: Remove via strong detergent and scrubbing, and if possible rinse by power washing. Check for adhesion before painting the whole floor to check for complete removal.
Delaminating plywood: Remove all loose splinters, thoroughly sand, prime with appropriate primer for chosen coating. Hi-Build epoxy primer helps fill and even the surface.
Things never to do (most common mistakes)
- Not doing the research on what your environmental conditions are and adapting the system to it.
- Not matching a suitable product to withstand the amount of traffic the floor will receive. In other words using too cheap of a product for the demands of the floor.
- Painting when the floor surface temperature (not the air) is less than 50 degrees. (60 and above is much better). Floor painting is not necessarily good winter work.
- Not reading and following label instructions (such as how long to mix epoxies, proper primer, coverage rates, etc.).
- Not applying enough material. When dealing with floors more is usually better.
- Painting on inadequately prepared surfaces.
Have further questions or need someone to check out your floor? Call our Customer Care Center at 866-498-7391 to schedule a walkthrough or use our Request an Estimate form.
Disclaimer: While we do our best to insure the information we provide is accurate we assume no risk and make no representations or warranty of any kind regarding the safety, completeness, accuracy, reliability, level of competency required, or suitability of any tips, 'how -to', posts, articles or explanations provided here. Any reliance you place on such information is strictly at your own risk so please review, take appropriate precautions and remember to always make safety your first priority.
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