One advantage of precisely pressed interlocking blocks is that the walls can look good with very little finishing. But “no finish” is not always the right choice. Here are the main options and what to think about for each.

Option 1: Leave the blocks exposed

Accurate blocks and neat laying give a clean, attractive wall with a natural earth colour. It saves plaster and paint and shows the craftsmanship. The trade-offs are that the surface is textured and can collect dust, and exposed blocks rely more on a good roof overhang and a sound plinth to stay dry.

Option 2: Pointing and sealing

Pointing fills the joints neatly, and a breathable sealer can reduce water absorption and dusting. Use products recommended for earth or cement-stabilised walls, and test a small area first. Avoid film-forming coatings that trap moisture.

Option 3: Plaster or render

Plaster gives a smooth, uniform surface and some extra weather protection. For good adhesion:

• Make sure walls are fully cured and free of dust and loose particles.
• Dampen the wall surface before applying plaster so it does not suck water out of the mix.
• Apply in thin coats and cure each coat, rather than one thick layer.
• Choose a plaster mix that is not stronger than the wall behind it, to reduce cracking.

Option 4: Paint

Use a breathable exterior paint over plaster or sealed blocks. Paint chosen for sealed concrete surfaces may peel from earth walls over time.

Combining finishes

A common approach is to leave interior walls exposed or lightly sealed, and protect exterior walls with a good overhang, a splash-proof plinth and, where required, a compatible render.

Think about maintenance

Any finish needs inspection. Cracks, blistering and stains are signs that water is getting in somewhere. Fix the source (a leaking gutter, a blocked drain) before repainting.

Related reading

See protecting earth block walls from rain for design details that reduce the need for heavy finishes, and our costing worksheet to include finishing in your comparison.

• interlocking blocks
• plaster
• wall finishes