What is base render? The sound backing under every finish

Base render is a coarse plaster of cement, sand and water used on walls, ceilings and façades. It levels the surface and prepares a strong backing for the finishing layers, giving durability inside and out.

What it provides

• Durability: protects walls against impact, damp and weather.
• A sound backing: a rough, strong substrate for plaster, paint and tile.
• Moisture resistance: forms a protective layer, especially on façades.

The mix

Cement binds, sand gives body and strength, water sets the consistency. Get the ratio wrong and the render either cracks or fails to bond.

Stages

1. Preparation: the wall is cleaned of dust and loose material, then dampened.
2. Mixing: cement, sand and water are combined at the stated ratio.
3. Application: the mortar is thrown on with a trowel and ruled off straight.
4. Curing: the surface is left to dry before any finish goes on.

Types

• Machine applied: fast and homogeneous.
• Hand applied: the traditional method.
• Façade grade: prepared with additives for exterior exposure.

Where it is used

Internal walls, ceilings, façades, balconies and terraces, and wet areas.

Points to watch

• The substrate must be clean and dampened.
• Keep the mix ratio right — neither too wet nor too dry.
• Do not apply in extreme heat, wind or rain.
• Never finish over render that has not cured.