Regularly sealing concrete maintains its longevity and durability for decades to come. Exterior surfaces need protection from the extreme temperatures, inclement weather, heavy impacts, or harsh abrasion. Interior surfaces benefit from sealants that offer protection against heavy foot-traffic, damaging cleaning supplies, and staining.
New Concrete Surfaces
For new concrete, allow at least one month for it to cure completely before applying a sealant.
Cleaning and Damage Repair to Existing Concrete Surfaces
No matter what kind of surface you’re sealing or sealer you’re using, unless you have freshly poured the concrete, the first step of the process is always to prep the surface with a thorough cleaning. You will need to either repair or resurface the concrete if any damage exists. From that point on, the processes differ slightly depending on the specifics of your project.
After giving an exterior surface a good power wash or after sweeping and scrubbing indoor surfaces, check the condition of your concrete surface. Some surfaces may need to be sanded or ground until perfectly smooth for the sealant to bond appropriately. Penetrating sealers are more forgiving in this regard than acrylic, epoxy, or polyurethane sealants.
If the concrete already has had sealant applied, we recommend stripping it from the surface before resealing. The exception to this is if you are applying the same brand of sealant and the manufacturer recommends layering applications over time.
For both interior and exterior surfaces, allow 24 hours for all moisture on the surface from cleaning or stripping concrete to dry after cleaning before applying a sealer.
Also, before using any sealant, damaged areas in the concrete surface must be repaired. Any surface that is not smooth due to pitting, cracks, erosion, or spalling must be patched and repaired or resurfaced completely before applying a sealer. Allow for appropriate drying time of any repair materials used.
For indoor surfaces, before repairing any damaged areas or applying any sealer, use a degreaser to ensure the materials will bond appropriately. For outdoor spaces, make sure that any materials such as oil or paint are removed using solvents, detergent, or acid. Allow 24 hours drying time after applying and scrubbing off any cleaning agents.
Once you have a smooth, clean, dry surface to work with, you’re almost ready to apply the sealer.
Preparing the Work Space
For interior concrete surfaces, remove trim such as molding and baseboards. You may also want to use protective tape or sheeting to adjacent surfaces.
For exterior surfaces, the most important step before applying a sealer is to check the weather. Most sealants require a minimum of 50°F and a maximum of 90°F for application, and you’ll want to avoid rain for the duration of the application process as well as a 5-day curing period for most sealant types.
Applying the Concrete Sealer
Follow the manufacturer’s instructions as to the recommended number of coats to use, whether you should use a roller or sprayer for application, and the drying time necessary for curing. Typically, curing time is 1-2 days, and most sealers will require a two-coat application.
Some penetrating sealers may even need three or more coats. Some sealers, such as polyurethanes have high levels of VOCs (volatile organic compounds) so be aware that a respirator or mask may be needed.
For more information on how to seal indoor and outdoor spaces, check out the steps and images in the following guides from WikiHow:
And this from Lowes: