Expert Painters

Limewash and Mineral Paint on Melbourne Brick

02 Nov

There is a reason the painted brick on a 1890s Richmond terrace often looks worse after ten years than the unpainted brick next door looks after a hundred.

Solid brick walls built before about 1920 were designed to breathe. They have no cavity and often no damp-proof course, so moisture that gets in has to leave through the face of the brick. Modern acrylic paint forms a plastic film that stops it doing that, and the moisture then leaves by pushing the face off the brick instead.

Limewash and mineral paint are the two finishes that colour old brick without sealing it.

What they actually are

They are different products and people use the names loosely.

Limewash is slaked lime and water, with pigment if you want colour. It does not sit on the surface as a film. It soaks in and then cures by reacting with carbon dioxide in the air, turning back into a form of limestone bonded into the brick. The finish is soft, slightly mottled and matt.

Mineral or silicate paint uses potassium silicate as the binder. It bonds chemically with the masonry rather than sticking to it, and it is tougher and more consistent in colour than limewash while still being highly breathable. It is usually the better choice where you want an even finish or a stronger colour.

Both let water vapour pass straight through. That is the entire point.

When they are the right answer

  • Solid brick walls from before roughly 1920, with no cavity
  • Any wall showing salt deposits, powdery mortar or paint lifting near ground level, which are signs moisture is moving through the masonry
  • Heritage overlay properties, where breathable mineral finishes are usually viewed far more favourably than acrylic
  • Brick that is already limewashed or lime-rendered
  • Where you want a soft, weathered look rather than a flat even one

If you have seen white crystalline bloom on a brick wall, read our notes on efflorescence first. It is the clearest signal that a breathable system is the only sensible option.

When they are not

Being straight about the limits:

  • If the brick is already coated in acrylic, limewash will not bond to it. The old coating has to be removed, which is slow and can damage the brick face, or you accept a mineral paint over a suitable mineral primer
  • Modern brick veneer with a cavity does not need breathability in the same way, and ordinary masonry paint is fine
  • Limewash is not a waterproofing product and will not fix a leak or a failed flashing
  • On a very exposed wall it weathers faster and will want attention sooner

The look is the trade-off, in both directions

Limewash does not give you a flat, even colour, and it is not meant to. It varies with how the brick absorbs it, it is lighter where the wall is dense and deeper where it is porous, and it keeps moving for the first few weeks as it cures.

Some people love that and choose it for exactly that reason. Others are expecting the finish of a modern exterior paint and are disappointed on day two. Worth knowing which one you are before committing.

It also weathers rather than fails. Instead of peeling in sheets it thins gradually and patinas, which is why a refresh coat is a straightforward job rather than a strip-back.

How it goes on

The method matters more than the product.

  • The brick is cleaned and any failed mortar repointed first, using a lime mortar on an old wall rather than a hard cement one
  • The wall is dampened down before coating, so the limewash does not dry before it has penetrated
  • It goes on in several thin coats, brushed, not rolled or sprayed
  • Each coat is left to cure before the next
  • Work is avoided in direct hot sun or near frost, because both ruin the cure

A thick coat of limewash is a failed coat of limewash. It chalks off because it never carbonated properly all the way through.

Maintenance and cost

Expect a refresh every five to ten years depending on exposure, which sounds frequent compared with a fifteen-year acrylic. The difference is that the refresh is a wash and a coat rather than scraping a failed film off brickwork, so the lifetime cost is comparable and the wall is in better condition throughout.

Application labour is higher than ordinary painting because of the number of coats and the preparation. Where the alternative is repairing spalled brick caused by a sealed wall, it is the cheaper path.

Heritage overlays

Much of inner Melbourne sits under heritage overlay. Painting masonry that has never been painted can require a planning permit and is often refused, and that applies to limewash as much as acrylic.

The useful distinction when you talk to council is that limewash is a traditional, breathable and largely reversible treatment, which is a very different proposition from sealing a wall in acrylic. Confirm the position for your address before committing either way. Our guide to heritage colour schemes covers what tends to be accepted.

For brick that is already painted and staying that way, our notes on painting brick homes cover that case, and rendering is the other route where the brickwork is past showing.

What we do

  • Limewash and mineral silicate coatings on solid brick and lime render
  • Repointing in lime mortar before coating
  • Assessment of whether a wall actually needs a breathable system or not
  • Removal advice where acrylic has already been applied to an old wall
  • Refresh coats on existing limewashed walls

We are based in Richmond, surrounded by exactly this kind of housing, and work across the inner suburbs, bayside and coastal Victoria.

Call 0404 330 332. If you are not sure whether your wall is solid brick or veneer, send a photo of a window reveal and we can usually tell from that.

šŸ“ Our Service Areas Across Melbourne, the Mornington Peninsula, Surf Coast & Phillip Island

Melbourne & Bayside

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