How to Plaster a Brick Wall

Plastering a brick wall means applying a wet plaster coat over bare brickwork to create a smooth, paintable surface. The process is: prepare the brick, control the suction, apply a backing coat (bonding or a render), then finish with a skim coat. You can't just spread plaster straight onto dry, dusty brick — it will crack and pull off because the brick sucks the moisture out too fast. Preparation and suction control are what make plaster stick to brick.

When you can plaster over brick

• Internal bare brick walls — bonding coat + skim is the standard approach
• Sound, clean brickwork — free of dust, paint, grease and loose mortar
• Walls where you want a smooth finish over the masonry

You should not plaster directly over brick that is:

• Damp or showing rising damp — the cause must be fixed first
• Painted with a flaky or glossy coating that won't key
• Crumbling or has loose, soft mortar

Preparation

1. Clean the wall — remove dust, loose mortar, flaking paint and grease
2. Rake out loose mortar — any joints that are soft need raking back
3. Control suction — dry brick draws water out of plaster too fast. Wet the wall down (a mist, not a soak) before plastering, or use a bonding agent
4. Key the surface — if the brick is very smooth, create a mechanical key
5. Apply a bonding agent where needed, following the manufacturer's guidance

Skipping suction control is the most common reason plaster fails on brick — it dries before it bonds.

The backing coat

A backing coat (bonding plaster for internal walls, or a render for external) builds up the surface and gives a flat base. It's applied at several millimetres, ruled flat, and scratched while still wet to give a key for the skim. For external brickwork, a render is used instead — see our external plastering page.

The skim coat

Once the backing coat has set, a thin skim coat (1–3 mm) is applied for the smooth finish. The thickness and technique are the same as skimming any wall — see our skimming walls guide and skim thickness guide.

Internal vs external brickwork

• Internal — bonding coat + skim gives a smooth, paintable finish
• External — a render (sand and cement, or a modern render system) is used, not interior plaster. External walls need weather resistance, not just a smooth finish.

Render vs plaster on brick

For external brick walls, the correct material is render, not interior plaster. Render is designed to withstand weather. If you're considering a modern render finish, our K-render guide explains through-coloured render systems.

Older London brick walls

Many older London properties have solid brick walls that were originally plastered with lime. If the wall is solid and pre-1920s, a lime-based plaster is often the correct, breathable choice — modern gypsum on a solid brick wall can trap moisture. See our lime plastering guide for when lime is right.

Common mistakes

• Plastering onto dry, dusty brick without wetting or bonding
• Applying skim straight onto brick with no backing coat
• Plastering over damp brickwork
• Using interior plaster on an external wall
• Skipping the scratch key on the backing coat, so the skim doesn't bond

FAQ

Can you plaster directly onto brick? Yes, with the right preparation — clean the brick, control the suction, apply a backing coat, then skim. You can't spread a thin skim straight onto bare brick.

Do you need to wet the wall before plastering? Usually yes. Dry brick sucks moisture out of plaster too fast. A light misting (not soaking) or a bonding agent controls the suction.

Can you skim over bare brick? Not directly. You need a backing coat first to build a flat, keyed surface, then the skim on top.

What's the difference between plaster and render on brick? Plaster is for internal walls; render is for external walls and is designed to resist weather.

Should old brick walls be lime plastered? Often yes. Pre-1920s solid brick walls benefit from breathable lime plaster; modern gypsum can trap moisture.

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Got a bare brick wall you'd like plastered? Send London Plastering Service a few photos and tell us the property age, and we'll advise on the right plaster system and provide a free quote.