Sealing brickwork and masonry creates a breathable, water-repellent barrier that protects external walls from rain penetration, damp, frost damage and long-term deterioration, while still allowing moisture vapour to escape.

This makes masonry sealers ideal for older, exposed or porous brickwork where water ingress can lead to staining, mould and structural damage.

What you’ll need

Breathable masonry sealer, pressure washer or stiff brush, hose, pointing trowel or mortar gun (for repairs), low-pressure sprayer or roller and tray, large masonry brush, masking tape or plastic sheeting, gloves, goggles and mask.

1. Preparation

Clean the brickwork thoroughly, removing dirt, algae, moss and loose mortar using a stiff brush or pressure washer.
Allow the surface to dry completely before sealing.
Repair any cracked or missing mortar joints and allow repairs to cure.
Mask off windows, doors and adjacent surfaces to prevent staining.

2. Application

Apply the masonry sealer from the top down to prevent streaking.

Using a low-pressure sprayer, apply evenly in horizontal passes, holding the nozzle around 100–150mm from the surface.
Alternatively, use a roller or large masonry brush to work the sealer into both bricks and mortar joints.
Apply 1–2 coats until the surface is fully saturated, allowing a light run-down but avoiding puddling.

3. Drying & protection

Allow the sealer to cure fully in line with product instructions.
Once dry, water should bead on the surface, confirming effective waterproofing.
Reapply every 5–10 years, or when water no longer beads, to maintain protection.

Key tips

Always use a breathable masonry sealer to prevent trapped moisture and spalling.
Do not apply to painted or previously sealed brickwork.
Apply in dry weather, ideally above +10°C.
Ensure mortar joints are fully treated, as these are the most vulnerable areas.