How to Seal Your Slate Patio

  • 12-20 hours
  • Beginner
  • 100-1,200
What You'll Need
Stone Sealer
Oxygen Bleach
Stiff Broom
Paint Pan
Paint Roller
Paint Brush
Plastic Bucket
Soft Dry Cloth

Sealing a slate patio can enhance the color of the stone and make it impervious to stains, mold and algae growth. Here are the steps.

Step 1 – Preparations

If the slate patio is dirty or is infested with mold and algae growth, take some time to clean it. Pour water over the patio and use a stiff broom to dislodge any loose dirt and grime. Add a mild detergent to the water if the patio is greasy. Wash the surface thoroughly with water. If the patio has been darkened due to algae and mold growth, mix an oxygen bleach solution in a plastic bucket. Pour the solution over the stone and let it sit for about 10 minutes. Scrub the mold or algae growth and rinse thoroughly with water.

Step 2 – Allow the Stone to Dry

Never seal moist slate because that will only cause it to be harmed in the long run. Slate is porous and if it is moist, it means that there is more water trapped inside the stone. When it is sealed moist, the sealer will not hold onto the stone firmly. Moist will mix with the sealing compound, making it less potent. The hot dry season is the best time to apply a sealer because slate stones can dry completely. However, if the sealing is done during a cold season, use a fan to help hasten the drying process.

Step 3 – Sealing the Slate

Prepare the paint rollers, brush, and pan. Purchase a sealer designed for natural stones or for slate, and for outdoor use. Pour the contents of the sealer into the pan and dip the roller into it.

Apply a thin coating of sealer onto the surface and let it seep through the stone’s pores. Use a paintbrush to seal hard to reach areas. Leave the sealer to dry for about 10 minutes. Wipe the sealed surfaces to prevent films from developing. Wait for about 30 minutes to an hour before applying a thicker coat of sealer. Wipe the sealer with a soft dry cloth again after 10 minutes.

Sealers are designed differently, so read and follow the instructions provided by the manufacturer to ensure the correct application. Wait for the recommended drying time to pass before allowing the patio to be used fully.

Step 4 – Maintenance

After sealing, maintain the patio by cleaning. Clear acidic liquid right away if the patio has been contaminated with it (such as vinegar). Wet the entire patio with water and mop it well if it gets dirty. This is to help maximize the effect of the sealer.

The sealer’s effectiveness lasts for 2 to 3 years, so reseal the slate within three years, depending on the amount of traffic the patio gets every day. If the sealer’s effects are wearing off, reapply the sealer in the same manner as described above.