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Penetrating damp brick sealer: when the can is last

Updated: 22 October 2026

A damp patch appears on the inside face of an external wall after wind-driven rain, and a colourless silicone looks like the whole answer. Sometimes it is the last coat on sound, porous brick above the damp-proof course. Often the water is still arriving through a gutter, an open joint or a crack the spray will not bridge. The [stone sealer comparison](/hub/garden-supplies/stone-sealer) holds the seven amazon.co.uk cans in this set. A qualifying purchase from that page can earn us a commission at no extra cost to you. This page decides whether a penetrating damp brick sealer is even eligible before you name a brand.

A damp patch appears on the inside face of an external wall after wind-driven rain, and a colourless silicone looks like the whole answer. Sometimes it is the last coat on sound, porous brick above the damp-proof course.

Our top picks

Sika Everbuild 402 Water Seal, 5 litre

Best overall

Sika Everbuild 402 Water Seal, 5 litre
9.2/10about £13.80
View offer
SAFEGUARD Raincheck Eco water seal, 5 litre

Best value

SAFEGUARD Raincheck Eco water seal, 5 litre
8.1/10about £18.00
View offer
HG HG natural stone impregnator, 1 litre

Rank 3

HG HG natural stone impregnator, 1 litre
7.3/10about £25.43
View offer
On this page
  1. 1.What the stain usually is
  2. 2.When a colourless silicone is even discussed
  3. 3.The two large cans
  4. 4.Stops

What the stain usually is

Driving rain through porous brick leaves a pattern that tracks weather on that elevation. A leaking gutter or cracked downpipe leaves a vertical stain under the eaves. Failed pointing shows as open joints you can probe. Rising damp and condensation are different diagnoses again. Path and Patio and damp surveyors make the same practical point: a water repellent does not repair flashings, gutters or missing mortar. IHBC notes that failed pointing is often a symptom of a leaking gutter, not a reason to start with a colourless coat. Walk the outside before you open a basket. Clear the gutter, replace the broken shoe, and repoint open joints. Safeguard's Raincheck guide treats hairline cracks only up to about 0.3 mm as compatible with a spray. Wider gaps are masonry work. If you skip that order, the silicone can bead rain on the brick face while water still enters beside it. Once the water path is fixed, a repellent can reduce how much rain soaks into remaining porous faces.

When a colourless silicone is even discussed

The Brick Development Association's alteration and repair guide allows a colourless silicone on porous brick only after salts, cracks and inward drying are considered. Their rain-penetration note also warns that colourless treatments can slow evaporation if water still gets in through a gap. SPAB goes further on historic fabric and says colourless water repellents on old absorbent buildings are normally disastrous. IHBC echoes caution on historic walls. A modern cavity gable of porous facing brick, above a visible damp-proof course, with sound pointing and no paint, is the case Safeguard's application guide is written for: dry masonry, unpainted, above the damp-proof course, masked glass and plants, two coats, no rain for about a day. A pre-1919 solid wall with soft bricks and lime mortar is not the same brief. Ask someone who understands that fabric before you spray a Victorian elevation because an amazon title said brick. This page is not a conservation specification. It is a stop sign for casual coating of historic absorbent walls.
Sika Everbuild 402 Water Seal, 5 litre

Testsieger

Sika Everbuild 402 Water Seal, 5 litre
9.2/10about £13.80
View offer

The two large cans

Only after the wall is eligible do the two large listings matter. Everbuild 402 is the top pick for a confirmed 5 litre fill. Raincheck Eco is best value among the other cans scored 80 or above, with a breathable claim on the title. The best brick sealer page holds the score logic. Both are wall water repellents, not hearth impregnators and not bird-bath sprays. For coat timing, Everbuild wants the second coat within one hour on a surface that may be damp but not wet. Raincheck's guide wants dry masonry and a day without rain. The how to apply brick sealer page keeps those clocks apart. If you still need the fork between wall, patio and stain bottles, use the stone sealer buying guide. HG, Hotspot, NOON'S UP and Nano Z are the wrong family for a house elevation.

Stops

Height is a stop for a weekend job. If you cannot reach the wall safely from the ground or a stable platform you already know how to use, the can is not the hard part. Asbestos-cement garage or outbuilding sheets appear in a couple of Everbuild reviews. Those sheets are not a listed use on the product page in this capture. HSE guidance treats asbestos cement as a material you do not sand and do not treat as a load-bearing roof to walk on. This page gives no preparation steps. If that is the surface, stop and get proper advice. Below the damp-proof course is outside Safeguard's Raincheck application window. Fishponds are refused on Everbuild's sheet. Raincheck Universal's amazon kit does not prove a 5 litre fill in this file. Do not buy it as a complete wall system on title alone. When any of those conditions fail, the can waits.

Common questions

Will a sealer stop penetrating damp by itself?
Not if water still enters through gutters, open joints or cracks. The repellent only helps porous faces that are otherwise sound.
What do I fix before I buy a can?
Gutters, downpipes, flashings and pointing. Probe cracks. Anything wider than a hairline is masonry work first.
Is a Victorian solid wall the same job as a cavity gable?
No. Historic absorbent fabric is a specialist question. SPAB treats colourless repellents on old absorbent buildings as normally disastrous.
Can I spray below the damp-proof course?
Safeguard's Raincheck guide is written for work above the damp-proof course. Stay inside that window unless a professional says otherwise.
Everbuild or Raincheck Eco for this wall?
Both are wall water repellents in this set. Everbuild is the top pick on score and confirmed fill. Eco is best value among the other high scorers, with a breathable title claim.
What about painted render?
Do not use Everbuild on paint. The sheet refuses it, and a UK review darkened painted render.
The garage roof is old cement sheet. Can I coat it?
Not from this page. Asbestos cement needs specialist handling. These consumer reviews are not a method.
How much will 5 litres cover?
About 5 to 8 m² per litre on Everbuild's sheet, or about 3.5 m² per litre on Safeguard's current Eco page. Multiply carefully and keep a margin for porous brick.

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Sources

Public UK sources for this comparison. Prices, stars and review counts are the amazon.co.uk listings in this set, captured 19 October 2026. Page updated 22 October 2026.

  1. Sika Everbuild 402 Waterseal sheet, March 2023 (retrieved 22 October 2026)
  2. Safeguard Raincheck Eco water seal (retrieved 22 October 2026)
  3. Safeguard Raincheck application guide (retrieved 22 October 2026)
  4. HG natural stone impregnating protector (retrieved 22 October 2026)
  5. ECOPROTEC: sealing stone outdoors (retrieved 22 October 2026)
  6. Brick Development Association: alteration and repair of brickwork (retrieved 22 October 2026)
  7. SPAB: rainwater penetration (retrieved 22 October 2026)
  8. HSE: asbestos cement (a16) (retrieved 22 October 2026)