Polyurethane On Concrete? (Here’s How To Apply it)

Polyurethane sealers protect the surface underneath from water, moisture, scratches, and more. So, can you use polyurethane on concrete?

You can use polyurethane over the interior and exterior concrete surfaces. The polyurethane will form a thick and durable layer that will protect the concrete.

Polyurethane, when dry, forms a thick and glossy layer over the concrete. The thick layer is moisture and water-resistant. So, if you want the concrete to last longer, use polyurethane. 

However, you must know the right type of polyurethane and how to use polyurethane correctly on concrete surfaces. We explained all you need to know down below.

Oil-Based Polyurethane on Concrete

You can apply oil-based polyurethane over concrete. The oil-based polyurethane will produce a tough layer over concrete. Also, oil-based polyurethane has impressive adhesion qualities, so it sticks to concrete floors and patios. 

In comparison to water-based polyurethane, oil-based polyurethane lasts longer on concrete. That’s because oil-based polyurethane uses oil as its solvent, while water-based polyurethane uses water as its solvent. 

Since oil takes longer to evaporate, the paint particles of oil-based polyurethane have more time to harden before drying. This results in a tougher and more durable coating. However, this also means oil-based polyurethane takes longer to dry on concrete. 

However, for outdoor concrete, you must use exterior polyurethane. Exterior polyurethane is UV resistant and has more additives to protect the concrete from weather elements (rain). However, the finish won’t last long if you use interior polyurethane for exterior concrete. After a while, the rain will slowly varnish the interior polyurethane, exposing the concrete surface to water and moisture.

You must apply polyurethane or concrete sealer over concrete. If you don’t, water can damage the concrete by breaking down the materials the concrete is made of. But, if you apply a sealer, the concrete becomes water-resistant and lasts longer. 

Related Read: How To Paint Over Concrete Sealer?

Varathane vs. Varnish Polyurethane

You shouldn’t use varathane polyurethane over a concrete surface. If you apply varathane polyurethane over concrete, the finish will have a yellow-tinted color. 

Also, varathane polyurethane doesn’t stick well to self-leveling surfaces such as concrete. Plus, this sealer isn’t as durable as oil-based polyurethane. However, for low-traffic indoor concrete, you can use varathane polyurethane.

Use polyurethane varnish to get a glossy finish and maximum protection for concrete. This polyurethane self-levels and penetrates the concrete surface. It also protects the concrete from dust, debris, water, moisture, and scratches.

How To Apply Polyurethane On Concrete?

Concrete decks, floors, and patios are becoming more popular in public buildings and homes. To protect the concrete surface, you must seal it with a sealer, such as polyurethane. 

Besides the concrete surface, the polyurethane will also protect the paint used on concrete. So, if you paint concrete, use polyurethane to seal it. Here’s how to do it:

Here are a few steps that will teach you how to apply polyurethane on concrete.

1. Clean The Concrete

For polyurethane to stick, the concrete surface must be clean. No dust, debris, or stains. 

To clean un-painted concrete:

  1. Pour mineral spirits over oil spills, stains, or dirt.
  2. Use a cleaning brush to scrub the concrete surface. 
  3. Once the concrete surface is clean, remove the residue of the mineral spirit with clean water. 

You can use TSP or pre-paint cleaner as an alternative to mineral spirits.

To clean painted concrete:

  1. Use soapy warm water or TSP. 
  2. Pour the soapy water over the concrete and use a soft brush to scrub the dirt. 
  3. After you remove the dirt, clean the soap residue with clean water. 

To clean concrete floor: 

  1. Use a phosphoric acid cleaner or concrete cleaner. 
  2. Use a scrubbing broom, and scrub the dust off the floor. 
  3. To be more efficient, work in batches across the room. Or, buy a kit to resurface the floors. 
  4. Water down the whole floor with clean water. 

2. Wait For Concrete To Dry

To remove the cleaner residue from the concrete, use a power washer, or water hose.

Once the concrete is clean and the cleaner residue is removed, wait until the concrete is dry. To speed up the drying process of concrete, squeeze the water off the surface. However, you still must wait 1-3 days for the concrete to dry. 

3. Use Concrete Filler

If the concrete surface is cracked, has holes, or is damaged, you must fix it before applying polyurethane. If you don’t, the polyurethane will soak into the concrete holes, and the finish will be uneven. 

To repair concrete cracks:

  1. Use concrete filler or concrete restoration caulk.
  2. Squeeze the caulk into the cracks or holes and fill up as much as possible; don’t leave gaps between concrete cracks, and fill the holes full.
  3. Use a towel to remove the excess concrete restoration filler, and let it dry. 

4. Mix the Polyurethane

Before applying polyurethane, you must mix it. To mix polyurethane, use a turning stick to stir the sealer for 5 minutes. Don’t stir too hard because air can get trapped inside the polyurethane container, and you will get a bubbled polyurethane finish.

If you don’t mix the polyurethane, the finish will be inconsistent and won’t dry properly. 

5. Apply The Polyurethane

Once the concrete surface is clean and the polyurethane is mixed, apply it. To apply polyurethane over concrete, use a paint roller or paintbrush.

For a small concrete surface, use a paintbrush. Put the paintbrush inside the polyurethane container, and then apply thin coats of polyurethane. 

For larger surfaces, use a paint roller. Pour a small amount of polyurethane over the large concrete floor, then use a paint roller to spread the polyurethane equally. 

You must apply 1-2 coats for low-traffic concrete surfaces. For high-traffic surfaces, you need 3-4 coats of polyurethane

Wait until the first (or second) coat of polyurethane is dry before applying the next one. If you re-coat polyurethane too soon, the finish turns sticky. Optionally, you can sand between coats of polyurethane (except the final coat). 

Polyurethane Lifespan on Concrete

Water-based polyurethane can last up to 5 years on a concrete surface. In comparison, oil-based polyurethane lasts 10 years over a concrete surface.

However, the durability of the sealers also depends on how much the concrete is used. For high-traffic concrete, the polyurethane doesn’t last more than 3-4 years. For low-traffic concrete surfaces, the polyurethane lasts up to 10 years. 

The polyurethane lasts less if the concrete surface is exposed to rain or sunlight. That’s because polyurethane is only water-resistant, not waterproof. So, after a while, the rain will dissolve the polyurethane and expose the concrete to water.

Related Read: How To Apply Polyurethane on Metal?

Final Words

Polyurethane is a great choice for a concrete surface. It protects the concrete from water, moisture, scratches, dust, debris, and more. Polyurethane also protects the paint underneath, so the concrete will keep its color for years. 

However, you must use the right type of polyurethane. You must use oil-based or varnish polyurethane to get maximum protection. If you use varathane or water-based polyurethane, the sealer won’t protect the concrete as much. 

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