Sealing a Concrete Patio

As well as helping to reduce the risk of staining, allowing moss or even algae to grow on a concrete patio, effectively sealing concrete patio will create a barrier that can prevent moisture penetration into the concrete. This can help protect the concrete against the risk of cracking during cold weather, due to the expansion that occurs when water freezes and then melts.

Preparing a Patio for Sealant

The first thing to do is to get the patio as clean as possible. Obviously brush it first, or alternatively you can use a hose to thoroughly jet-wash it; both of these techniques will also remove any loose material - if this results in any unsightly cracks or breaks in the concrete patio, repair them before applying the sealant.

If the patio has any bad grease or oil stains that haven’t been removed, use a chemical like white-spirit to dissolve them away. You can then jet-wash the area again to remove the residue or throw buckets of water with a detergent in them over the area and brush it away; finally pour plain water over the area to dilute away any detergent still lying on the surface of the concrete patio.

If you have any paint on areas of the concrete patio that you want to remove - you’ll probably need to ‘blast’ the paint off with; shot, sand or dry ice. Apart from the cost of hiring such equipment; unless you’re used to operating it this might be a job best done by an expert.

Applying Penetrating Concrete Sealant

Check the weather reports for the day you want to apply the sealant. The temperature needs to be above 5 degrees C and ideally below 30 degrees C. The more important of these two is the lower temperature. Do not start to apply a concrete patio sealant if there’s a risk of frost, or if it is likely that there’ll be any sort of precipitation over a three to five day period.

Read the manufacturers instructions carefully for details of how to apply the product. Generally when applying a concrete patio sealer you first have to damp the concrete surface with water, making sure not to leave any standing water. The sealant can then be either sprayed or brushed onto the patio concrete.

As you’re sealing outdoor concrete you’ll probably need to apply at least a second coat. Before applying the second coat, make sure that the first one is thoroughly dry; this will probably mean leaving it overnight.

After applying the final coat of sealer as directed by the manufacturer, leave the sealer to work for 48 hours; then hose it down with clean water. This penetrating sealer adheres to the surface particles of the concrete and will require around 10 days to fully cure.

Adding Patio Top Sealer

When the 10 days is up, hose down the concrete patio again, you can then cover it with a top-sealer. This will make any liquid falling onto the concrete patio form small beads that can easily be brushed away. Ideally, and for the best results, spray the top sealer onto the damp concrete patio, if that’s not possible it can be brushed on. Whilst the first coat of curing compound itself is still damp - add a second layer then leave to dry for at least 36 hours. Your concrete patio is then fully sealed and ready for you to enjoy.