Exposed concrete (béton brut)

Exposed concrete takes its other name from the French béton brut, meaning raw concrete. Nothing is applied over it: no render, no paint, no cladding. The surface left by the formwork is the building’s final face. Le Corbusier’s Unité d’Habitation in Marseille is one of the best-known examples, and the approach gave its name to Brutalism. In Turkish it is called brüt beton.

Why it is hard to do well

With no finish on top, nothing can be hidden. The layout of formwork panels, the position of tie holes, the alignment of joints and the placing of concrete all need to be designed in advance. Poor vibration leaves voids; leaking formwork causes colour patches. Board-marked timber formwork prints a grain pattern onto the surface, while smooth plywood or steel forms give a cleaner, more contemporary look.

Practical points

• Using one mix and one formwork material on a surface keeps the colour consistent.
• Keep adequate cover so reinforcement never sits close to the face.
• On exteriors, a protective treatment reduces staining and water absorption.

Exposed concrete is a test of skill in visualisation too. A flat grey texture makes a scene look artificial. Add formwork joints, tie holes, slight tonal variation and a good roughness map, and the surface starts catching light like the real material.