How to Seal Concrete Patios

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What You'll Need
Stiff brush
Hose or pressure washer
Sandblaster or dry ice
Mild detergent
Stiff brush
Grease solvent
Muriatic acid
Silane/siloxane water repellent
Spray applicator

If concrete patios are not sealed they become vulnerable to moisture and staining. Rainwater and melted snow, even water sprayed from a garden hose to wash the patio, can penetrate the concrete surface and invite the growth of moss and algae. Additionally, there is always the risk that cement in colder climates will develop cracks from expanding ice that has seeped into the pores as water and froze. To avoid these potential problems, you should apply a sealer to your patio and reapply it as needed. Here are five steps that will guide you through to successfully completing this project.

Remove Dirt and Debris From the Surface

Clean the surface of your patio by removing all dirt, dust, and debris with a stiff brush. As an alternative, you can consider cleaning it by spraying the concrete with water, however, you will need to wait at least 24 hours to allow drying of the surface.

Remove Paint, Grease, and Oil Stains

For patios with old paint remaining on the surface, remove it by blasting with sand or dry ice. You may also find grease or oil stains remaining after sweeping or spraying your deck surface which will call for a different technique. Add detergent to a bucket of water, pour this on your deck, and use a stiff brush to scrub the affected areas. If this technique fails to work, use a grease solvent instead, or for grease that has penetrated the concrete pores and is hard to remove, apply a small amount of muriatic acid.

Safety Note: Always take care to protect your skin when working with muriatic acid.

Finally, rinse off any soapy water, solvent, paint residue, or acid with clean water before you allow the surface to dry.

Wait for Favorable Weather

Concrete sealers need moderate temperatures for the most effective application and the best curing. Avoid applying these sealers if you cannot count on at least three days when temperatures stay between 5 degrees Celsius and 30 degrees Celsius. Also, refrain from using a sealant if you expect precipitation during that three-day period.

Apply Sealer

Apply your choice of sealer, following any directions from the product's manufacturer for the tools you will need. It is best if you start from one corner of the patio and work backward toward the opposite end. More than likely you will need to add a second coat, but be sure to allow the first to dry overnight before you do. If outside temperatures are low, allow an extra day to be sure the first coat is thoroughly dry. Give your second layer a full 48 hours to cure after you've spread it on. Then, hose it off with a garden hose, and give it 10 days to allow the sealer to fully adhere.

Apply Top Sealer

For best results, hose down the surface again after your 10-day waiting period, and then spray on the top sealer. If you don't have a spray applicator, pour this onto the damp surface and spread it with a brush instead. Before this coat is completely dry, apply a second, and allow a minimum of 36 hours before allowing foot traffic on the surface.

With a successful sealer application, your concrete patio should remain protected for a very long time.