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How to clean and seal a crazy stone porch?

Porch has been neglected for a few years now (5) and is in need of a good scrub and seal. I'm pretty sure the tiles are slate and the mortar bits would be sandstone.

I was going to acid wash it but that will be too harsh. I gave her a straight up pressure wash but some of the moss/grime is very stubborn so am looking for an appropriate agent to use.

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MitchellMc

Hi @splinters,

It sounds like your porch is in need of a bit of TLC after a few years of neglect. Since you've already given it a pressure wash and are dealing with some stubborn moss and grime, using a chemical cleaner like 30 Seconds Outdoor Cleaner is a great next step. This type of cleaner is designed to tackle mould, mildew, algae, and grime on porous surfaces like slate and sandstone. It's also less harsh than acid washing, which can be too aggressive on softer materials like sandstone mortar.

Once you apply the cleaner, give it time to work its way into the surface—about 10-15 minutes—and then scrub the area thoroughly with a stiff bristle brush. Make sure to keep the surface wet as you scrub, and rinse it off with water afterwards. This should help lift off the stubborn grime without damaging the tiles or mortar.

After cleaning, it's a good idea to seal the slate tiles to protect them from future dirt, moss, and water penetration. Slate is a porous material, so sealing it will help preserve its appearance and make future cleaning much easier. A product like Crommelin Slate Sealer would be a good option to consider. Before applying the sealer, ensure the porch is completely dry to prevent trapping any moisture under the seal.

Let me know if you have any questions about the cleaning process or sealing products.

Mitchell

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