What is limewash, and is it right for your house?

Limewash is lime, water and pigment that soaks into the wall

Limewash is a coating of lime and water, tinted with pigment, that sinks into the surface instead of sitting on top. Rockcote, which makes its products on Queensland's Sunshine Coast, says traditional lime wash is made from limestone and water, with pigments added when colour is needed. It says limewash works particularly well on open-textured surfaces because it can soak into them.

The look is the whole point. Rockcote describes a flat, chalky finish with subtle colour changes, and says the end result shifts with the wall, the brush work, the colour and the number of coats. Porter's Paints says that as the lime cures it "blooms", giving natural colour variation and often slight streaking. That variation shows more in deeper colours.

Two more things catch people out. Limewash looks darker when it's wet and lightens as it dries, so Rockcote suggests a sample area first. And lime absorbs carbon dioxide as it cures, according to Rockcote.

Limewash works on bare, absorbent masonry, and not on timber or fibre cement

Limewash suits bare masonry that drinks in water, and it fails on anything smooth, non-porous or flexible. Porter's says its Original Lime Wash can go on cement render, bagged brickwork, concrete, masonry blocks, bricks, mud brick, sandstone, off-form and tilt-up concrete, and most absorbent stone. It performs best on bare, clean masonry with even porosity.

The no list is just as clear. Porter's says limewash isn't suitable for fibre cement sheeting or other sheet products, wood, metal, glazed tiles, glazed bricks or non-porous surfaces, and it isn't a floor paint. So if you've been searching for limewash on timber, the answer from the maker is no. Porter's explains the sheet problem too: limewash is a hard finish, a flexible sheet can crack it, and the joints shadow through when the wall gets wet.

New walls need time first. Porter's lists minimum curing times before limewash goes on:

Inside the house it's a different product. Porter's Original Lime Wash is for exteriors, and the company points interiors to Interno Lime Wash, which it says can go on prepared plasterboard, plaster, masonry and previously painted surfaces. Porter's adds that Interno can be over-coated with Matt Wall Sealer for extra protection and a wipeable finish. For brick in particular, read our guide to limewash on brick.

Limewash over existing paint needs a sealer coat first

Yes, you can limewash over old paint, but only once the paint is sound and sealed with a primer made for the job. Porter's prep for previously painted walls goes like this:

1. Make it sound. Scrape off loose, peeling or flaking paint.
2. Fill and sand. Fill holes and cracks, sand and dust off.
3. Spot prime, then seal the lot. Spot prime the repairs with Porter's Limeproof Undercoat Sealer, then put one coat of it over the whole wall. Porter's says it's touch dry in two hours and needs six hours before limewash.
4. Do the trims first. Porter's says to finish painting all nearby surfaces and trims before the limewash starts.

Modern render can be a trap. Porter's says the acrylic in many modern renders cuts down how much they absorb, so limewash doesn't stick properly. Its advice is a small test patch. If the patch fails, or you're not sure, two coats of Limeproof Undercoat Sealer go on first.

Watch for white salt on the wall too. Porter's says efflorescence comes from water getting into the masonry, and the source of that water should be found and stopped before limewash. The wall should also be clean and free of loose material, dirt, grease, oil and mould. Our guide to painting rendered walls covers the acrylic route on render.

Limewash and acrylic paint do different jobs

Limewash and acrylic exterior paint suit different walls and different owners, so neither one wins on every count. Here's how one traditional exterior limewash and one acrylic exterior paint compare, using only what each maker says about its own product.

Read the table for fit, not for a winner. Limewash gives a soft, shifting, aged look on bare masonry, and it's meant to wear back over the years. Acrylic gives an even colour on a much wider range of walls, including timber weatherboards, and goes on faster. For acrylic choices near the beach, see our guide to the best exterior paint for coastal homes.

Limewash wears away over about 10 to 12 years, and that's by design

Limewash lasts about 10 to 12 years on masonry, including brick, before it needs redoing, going by Porter's. It says the finish stays soft and slowly washes away over that time, depending on the climate, and that weathering speeds up in high rainfall areas or damp conditions. Over a sealed, painted wall, the wearing coat can expose the undercoat, and that's when it needs repainting.

For context, the Bureau of Meteorology puts mean annual rainfall at Sunshine Coast Airport at 1,499mm. Use that with the maker's warning about rain when you plan how often you'll redo it.

Upkeep is gentle. Porter's says to wash with low-pressure water and a mild, acid-free detergent, and warns that harsh brushes or stiff brooms can scuff the soft lime. Rockcote goes further and says cleaning limewashed walls isn't recommended at all. If a spot needs touching up, it says to add another coat.

• Recoats look different. Porter's says new coats over old limewash show more contrast in the bloom.
• Patches can show. Porter's says to repaint the whole wall from edge to edge after a patch, and even then the patch can shadow through if its porosity is very different from the rest of the wall.
• Going back to acrylic is possible. Porter's says to wash the limewash back to a stable surface or remove it, apply two coats of Limeproof Undercoat Sealer and let it dry a full 24 hours first.

On the Sunshine Coast, the hard part is curing it in the right weather

Limewash on the coast is all about the weather window, because it needs mild days and mild nights to cure. Porter's says not to apply it in high humidity, below 10°C or above 30°C, or onto a wall colder than 10°C. It also says the wall shouldn't stay damp into the evening if the night will drop below 14°C. Cold stops the lime curing and can leave a whitish bloom in patches or over the whole wall.

Now put that next to the Bureau of Meteorology averages for Sunshine Coast Airport. The mean minimum is under 14°C from May (13.8°C) through to September (13.0°C), with July lowest at 9.7°C. In October it's back up to 15.8°C. January's mean maximum is 29.1°C, just under the maker's top limit, so summer jobs need care on hot walls. Porter's says to work in the shade on hot, dry or windy days, following the sun around the house.

Rain is the other risk. Porter's says the final coat has to be water cured: mist it lightly, let it dry, and repeat at least six times. Limewash that hasn't cured properly and then gets rained on can develop a chalky white film or heavy white streaks. So check the forecast before the last coat. For acrylic timing, see the best time to paint a house exterior.

Why limewash takes longer to put on than acrylic paint

Limewash takes more time on the wall than acrylic, because every coat has extra steps and longer waits. Our instant estimate doesn't price limewash, so we won't guess a figure here. Our exterior house painting cost guide covers acrylic repaints. Here's the work the Porter's sheet asks for:

• Dampen bare masonry evenly first, so the wall doesn't suck the water out of the limewash. Porter's says that can make it brittle and chalky.
• Brush it on with a block brush in a random "crow's feet" pattern, worked into the texture.
• Keep a wet edge the whole time and finish each wall at a corner or joint, since a stop mid-wall can leave a mark.
• Wait at least 8 hours between coats, ideally overnight, against 2 hours for Weathershield.
• Mist cure the final coat at least six times.

Porter's says limewash is a very traditional recipe, so it asks for a highly skilled painter who knows the product's limits. Rockcote also suggests an experienced applicator for a more even result.

Upper walls on a two-storey house are a job for a professional with scaffold, not a ladder. Safe Work Australia says construction work with a risk of falling more than 2 metres is high risk construction work, and lists scaffolding among the ways to prevent falls. Keep any DIY limewash to walls you can reach from the ground.

In Queensland, the QBCC says anyone you pay to do building work valued over $3,300 must hold a QBCC licence. We hold QBCC licence 1281728 and work across the Sunshine Coast, from Sunshine Beach to Caloundra. For architectural homes, see our high end painters in Noosa page, or talk to our high end project painters or exterior house painters. Get a free quote and we'll look at the walls on a free site visit.