Which paint should I use on exterior masonry?
Which paint should I use on exterior masonry?
A breathable mineral or masonry paint — and on an old solid wall, breathability matters more than any durability claim.
Older buildings with solid walls and lime mortar are designed to get wet and dry out again, and sealing them with an impermeable coating interrupts the drying half of that cycle. Water then finds another route in — around a window, through a defective gutter — and cannot get out, producing internal damp that is blamed on rising damp and frost damage that spalls the face off the bricks. That is the single most consequential decision here. Beyond it, preparation dominates the result: chalky or powdery surfaces need a stabilising solution, algae need a fungicidal wash rather than a stiff brush, and any cracks or defective pointing need repair, since paint bridging a moving crack will simply split again.
The options, ranked
| Option | Good at | Bad at |
|---|---|---|
| Mineral (silicate) paint | Bonds chemically into the substrate and is highly vapour-permeable, so moisture can leave the wall. | Alkaline and limited to mineral substrates; it will not go over old plastic-based coatings. |
| Breathable acrylic masonry paint | Straightforward to apply, wide colour range, and permeable enough for most modern walls. | Permeability varies enormously between products; the figure has to be checked rather than assumed. |
| Limewash | The traditional finish for solid lime-mortared walls: extremely breathable and self-healing. | Needs frequent renewal and does not suit cement-rendered or modern walls. |
| Textured or waterproof masonry coating | Bridges hairline cracks and is heavily marketed as a permanent solution. | Traps moisture in a solid wall, which causes damp inside and frost spalling outside. |
Technique that changes the outcome
- Wash down and treat any algae or moss with a fungicidal wash, then let the wall dry properly
- Apply stabilising solution to chalky or previously distempered surfaces
- Repair pointing and cracks before painting, not after
- Check the paint's vapour permeability figure on the data sheet if the building is old
- Paint out of direct sun and not in the two days before frost
What goes wrong
- Impermeable "waterproof" coatings on solid walls
- Painting over damp masonry, which blisters within a season
- Cement-based repairs on a lime-mortared wall
Compiled practical guidance rather than a published standard. Product formulations vary by brand and market, so read the label — and where the work is structural, electrical or gas, the regulations that apply where you are govern rather than anything here.
Other paint questions
| For | Use |
|---|---|
| Previously painted wood | Clean it, key it and spot-prime bare areas — and find out first whether the existing paint is oil or water based. |
| Bare wood | Knotting solution on the knots, a wood primer, then your topcoat — and prime end grain twice. |
| Plastic | Any paint, provided an adhesion promoter goes on first — and on polypropylene or polyethylene, the promoter is not optional. |
| Kitchens | A scrubbable acrylic eggshell or satin on the walls — and for cabinets, degrease, prime and use a proper cabinet enamel. |
| Bathrooms | A moisture-resistant acrylic in a satin or eggshell sheen with a mould inhibitor — but ventilation, not paint, is the actual fix. |
| Metal | Remove the rust, apply a rust-inhibiting primer the same day, then an alkyd or a direct-to-metal acrylic. |
| Ceilings | A flat matt emulsion — and if there is a water stain or nicotine, seal it with a shellac-based stain block first. |
| Tiles | Tile paint over an epoxy or adhesion primer on a thoroughly degreased and abraded glaze — and expect a limited life in a shower. |
| Fences | A penetrating stain or fence treatment rather than a film-forming paint — and let new pressure-treated timber weather first. |
| Floors | Two-pack epoxy on concrete after a moisture test and a proper grind; floor-grade varnish or floor paint on timber. |
| Radiators | A radiator enamel — water-based acrylic ones no longer yellow, which ordinary gloss on a hot surface always will. |
| Galvanised metal | A mordant wash, a self-etch primer or a purpose-made acrylic primer for galvanising — ordinary oil-based primer peels off in sheets. |
| UPVC | A uPVC-specific paint or an adhesion promoter with an acrylic topcoat — and avoid dark colours, which can distort the frame. |
Common questions
- Which paint should I use on exterior masonry?
- A breathable mineral or masonry paint — and on an old solid wall, breathability matters more than any durability claim.
- What should I avoid?
- Impermeable "waterproof" coatings on solid walls Painting over damp masonry, which blisters within a season Cement-based repairs on a lime-mortared wall
Related pages
- Which paint goes over previously painted wood? Clean it, key it and spot-prime bare areas — and find out first whether the existing paint is oil or water based.
- Which paint should I use on bare wood? Knotting solution on the knots, a wood primer, then your topcoat — and prime end grain twice.
- Which paint sticks to plastic? Any paint, provided an adhesion promoter goes on first — and on polypropylene or polyethylene, the promoter is not optional.
- Which paint should I use in a kitchen? A scrubbable acrylic eggshell or satin on the walls — and for cabinets, degrease, prime and use a proper cabinet enamel.
- Which paint should I use in a bathroom? A moisture-resistant acrylic in a satin or eggshell sheen with a mould inhibitor — but ventilation, not paint, is the actual fix.
- Which paint should I use on metal? Remove the rust, apply a rust-inhibiting primer the same day, then an alkyd or a direct-to-metal acrylic.
- Which paint should I use on a ceiling? A flat matt emulsion — and if there is a water stain or nicotine, seal it with a shellac-based stain block first.
- Which paint can I use on tiles? Tile paint over an epoxy or adhesion primer on a thoroughly degreased and abraded glaze — and expect a limited life in a shower.
- Which paint should I use on a fence? A penetrating stain or fence treatment rather than a film-forming paint — and let new pressure-treated timber weather first.
- Which paint should I use on a floor? Two-pack epoxy on concrete after a moisture test and a proper grind; floor-grade varnish or floor paint on timber.
Sources
- Typical range compiled from manufacturer specifications — At One Place