Breathable paint for brick: how to colour brick without trapping moisture
By the KEIM Australia technical team · Last updated 26 October 2026
Breathable paint for brick is a coating that lets water vapour move out of the wall instead of holding it behind a film. Look for a published vapour figure: KEIM Soldalit has an sd value of 0.01 m or less (class V1): the brick keeps drying while the colour bonds into the surface rather than sitting on top of it.
Brick has carried Australian homes for generations because it copes with heat, rain and salt air. The question we hear most is not whether you can paint brick, but how to do it without spoiling what makes brick work. Australian brickmaker PGH puts it simply: "Remember that bricks need to breathe" (PGH Bricks, painting brick guide). This guide explains what "breathable" means in numbers, which KEIM system fits which brick, and how to prepare the wall.
Why does brick need a breathable paint?
Brick needs a breathable paint because it takes up and releases moisture every day, and a coating that slows that drying can hold water in the wall. Rain, condensation, rising damp and humid nights all put moisture into masonry. A wall that can dry out stays healthier.
A film-forming coating sits on the face of the brick as a continuous skin. When vapour moving outwards meets that skin, it can collect behind it. That is when you see the classic failures on painted masonry: blistering, flaking and paint that lifts away in sheets. PGH also warns that removing paint from brick "usually requires the use of chemicals" and is expensive, so it pays to choose the right system the first time.
What makes a paint "breathable"? (sd value and class V1)
A paint is breathable when its resistance to water vapour is very low, which is measured as an sd value and grouped into classes under EN 1062-1. The sd value is the thickness of still air that would resist vapour as much as the coating does. Lower is better.
What to check | KEIM Soldalit (TDS 09/2026) | What it means on site |
sd value | ≤ 0.01 m | The coating resists vapour like a centimetre of still air or less |
Vapour class | V1 (high permeability) | The top class for vapour-open coatings |
Water uptake | W3 (low) | Rain is kept out while vapour still gets out |
Finish | G3 matt (85°) | A mineral, non-shiny look that suits brick |
Colour fastness | A1 (BFS Leaflet No. 26) | Inorganic pigments that stand up to UV |
The useful pairing is W3 with V1: water is kept out from the weather side, and vapour can still leave from inside. If a product does not publish an sd value or vapour class, ask for it before it goes on a brick wall.
Takeaway: Before you paint brick, ask the supplier for two numbers: the sd value and the water uptake class. "Breathable" on the tin is not a specification.
How is mineral silicate paint different on brick?
Mineral silicate paint bonds chemically with the mineral surface instead of forming a separate skin. The silicate binder reacts with the substrate (silicification), so the colour becomes part of the outer layer of the wall. With nothing sitting on top as a film, there is nothing to blister or peel away from the brick.
KEIM Soldalit is a sol-silicate paint: it bonds with mineral substrates and also works over sound, load-bearing dispersion and silicone resin paints and plasters, which helps on brick that was painted before. Its organic content is under 5 %, so we describe it as a mineral silicate system, not as "100 % mineral". Learn how the reaction works on our Learning Hub.
Paint or glaze: which KEIM system suits your brick?
Choose an opaque paint when you want a new, even colour, and a glaze when you want to keep the brick's texture and variation visible.
KEIM Soldalit gives a solid matt colour across face brick, bagged brick or previously painted brick. Two coats: a primer coat diluted up to 5 % with Soldalit-Fixativ (up to 10 % on very absorbent surfaces), then the finish coat. See KEIM Soldalit.
KEIM Concretal-Lasur is a translucent mineral glaze. At Shiel Street, North Melbourne, Clare Cousins Architects had salvaged bricks finished in KEIM Concretal-Lasur, applied by Total Painting Group, so the brick still reads as brick (project details). See KEIM Concretal-Lasur.
Heritage brick: at Parramatta Town Hall (1883), the stuccoed brickwork was restored with KEIM Royalan, a vapour-permeable mineral silicate system, with KEIM Faceal Oleo as the clear protective finish. Heritage advice from TKD Architects; applicator Fine Touch.
How do you prepare brick for breathable paint?
Prepare brick so it is sound, clean, dry and free of loose material before the first coat. Mineral paint does not hide a weak surface: it bonds with whatever is there.
Check the wall. PGH notes that damaged bricks or walls affected by moisture are poor candidates for paint. Fix the cause of damp first.
Clean and repoint. Clean the brickwork and repoint where needed; seal cracks before painting (PGH).
Deal with old coatings. Loose or flaking paint must come off. Sound old acrylic can stay if a test area shows good adhesion; KEIM Soldalit-Grob can even out texture and fine hairline cracks as a base coat under Soldalit.
Watch for salts. White crystalline deposits (efflorescence) mean moisture and salts are moving. Substrates with salt efflorescence are listed as unsuitable on the Soldalit data sheet, so solve the moisture first.
Pick the weather. Air and wall at 5 °C or more, and not in direct sun or on a sun-heated wall (Soldalit TDS).
Do a sample. Paint a test area and look at it in morning and afternoon light. Order colour samples and check the technical datasheets before you quote.
Key points
Brick needs to dry out; a breathable paint lets vapour leave instead of trapping it.
Ask for numbers: sd value (lower is better) and vapour class V1.
KEIM Soldalit: sd ≤ 0.01 m, V1, W3, G3 matt, A1 colour fastness (TDS 09/2026).
Use Soldalit for solid colour, Concretal-Lasur to keep brick texture visible.
Fix moisture and salts before painting; never paint in direct sun.
FAQ
Can you use breathable paint on old painted brick?
Yes, if the old coating is sound and well bonded. KEIM Soldalit is suitable over load-bearing dispersion and silicone resin paints, and KEIM Soldalit-Grob can be used as a base coat to even out texture and fine hairline cracks. Loose, flaking or elastic coatings have to be removed first. Always do an adhesion test on a small area before quoting the whole wall.
What does an sd value of 0.01 m mean?
It means the paint resists water vapour about as much as a one-centimetre layer of still air. The lower the sd value, the more freely vapour moves through the coating. Coatings below 0.14 m fall into class V1, the most vapour-open class under EN 1062-1. KEIM Soldalit's data sheet lists an sd value of 0.01 m or less.
Will breathable paint stop rain getting into my brick?
A good breathable paint keeps liquid water out while letting vapour out. KEIM Soldalit is rated W3, the low water-uptake class, as well as V1 for vapour. It will not fix leaking gutters, failed flashings or rising damp, so those problems need repairing before you paint. Paint is the last layer of protection, not the first.
Should I paint brick or use a glaze?
Choose paint if you want a new, even colour that hides old patches. Choose a mineral glaze such as KEIM Concretal-Lasur if you like the texture and colour variation of the brick and want to tone or unify it. Both are mineral systems that bond with the surface. A sample patch on your own wall is the best way to decide.
How many coats of KEIM Soldalit does brick need?
Two: a primer coat diluted with KEIM Soldalit-Fixativ (up to 5 %, or up to 10 % on very absorbent brick) and a finish coat. The data sheet gives about 0.35 to 0.5 kg per square metre for the two coats on smooth surfaces; textured or very absorbent brick uses more, so estimate from a test area.
Sources: KEIM Soldalit technical data sheet 09/2026; PGH Bricks painting brick guide; KEIM Australia project pages for Shiel Street and Parramatta Town Hall.
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