Why Seal Brick and Masonry
Brick is porous by nature, so an unsealed wall absorbs water, dust and oil every time it rains. Left unchecked, that moisture leads to damp, frost damage, efflorescence (the white salt staining you sometimes see on older brick) and gradual wear on the surface. A breathable sealer creates a water-repellent barrier that:
- Cuts water absorption by filling the porous voids in the brick
- Helps prevent frost damage and the cracking or flaking it causes
- Limits efflorescence
- Resists algae, mildew and general organic growth
- Protects the surface without changing how the brick looks
What Sealing Protects Against
- Water penetration. Rain soaks into unsealed brick, especially on exposed elevations, and that's the moisture behind most of the problems below.
- Frost damage. Water trapped in the brick expands by around nine per cent when it freezes, which is what forces the surface to crack or flake off.
- Efflorescence. The white salt deposits that form as moisture moves through the masonry.
- Damp indoors. Water getting into an exterior wall can show up as a damp patch on the inside face too.
- Surface build-up. Dirt, oil staining, mildew and algae all take hold more easily on a wall that stays damp.
Penetrating Sealer vs Surface Coating
There are two ways to seal brick, and they behave very differently:
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Penetrating sealer soaks into the masonry rather than sitting on top. It keeps the natural look of the brick, stays breathable, and is the right choice for facing brickwork you don't want to change the appearance of. SplashGuard works this way: it dries clear and forms an invisible barrier below the surface.
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Surface coating forms a visible film on top of the wall. It can change the appearance and reduces how well the wall breathes, so it suits decorative finishes more than traditional brick or stone.
For most exterior brick and stone, a breathable penetrating sealer is the safer choice, because trapping moisture behind a film coating is what causes coatings to bubble and brick faces to blow in winter.
Sealing a damp wall. Most sealers need a dry spell to work properly, which is awkward if you're dealing with a wall that's already wet, or you're working over winter. Storm Seal is built for exactly that: a breathable water-seal you can apply straight onto damp brick and masonry, so you're not stuck waiting for the weather before you can protect the wall.
How to Apply Brick Sealer
Clean the wall thoroughly first, removing dust, dirt, oil and any algae or mildew, and repair any cracked or damaged mortar before you start. Protect windows, doors and anything nearby from overspray or drips.
Apply two coats on porous brick, sandstone and limestone, letting the first coat fully cure before the second, roughly 12 hours apart. Denser materials such as granite or engineering brick need one coat. You can apply by brush, roller or low-pressure sprayer. It's worth testing on a small, unseen patch first, especially on specialist bricks or brick slips, to check the finish and how much it absorbs. Aim for a dry day and follow the product's instructions for the best result, or reach for Storm Seal if the wall's already damp and drying it out first isn't practical.
Interior Brick and Stone
Not every job is exterior. If you've got exposed interior brick, our Interior Stone and Brick Sealers range is built for indoor use, and our Stone and Brick Cleaners are worth using first if the wall needs a clean before sealing.
Why Buy From Kingfisher
We're a family-run business, and we've made sealants and coatings in the Lake District since 1988. Everything's manufactured here in the UK, and we're ISO 9001 certified. If you're not sure which sealer suits your wall, our technical team's happy to talk it through before you buy, and you can collect from our Ulverston or Glasgow trade counters if that's easier than waiting on delivery.
Frequently Asked Questions
What does brick sealer do?
It reduces how much water the brick absorbs and protects against frost damage, staining and moisture-related wear by soaking into the porous surface and repelling water at the source.
Does brick sealer change the colour?
A penetrating sealer typically dries to a natural matt finish, so the look of the brick stays the same. It can look slightly darker straight after application, but that usually fades as it fully cures.
How long does masonry sealer last?
It depends on exposure and the condition of the wall it's going onto, but a properly applied breathable sealer is built to last for years, not months. Applying it correctly, on a clean, dry wall with the right number of coats, makes the biggest difference to how long it holds up.
Can brick sealer stop damp?
It helps by keeping rain from soaking into the wall in the first place, which deals with penetrating damp. It won't fix structural issues like rising damp, which need a different fix; a chemical damp proof course rather than a surface sealer.
