THE SCALE - BRE Digest 251 Assessment of Damage to Low-Rise Buildings

Aesthetic - Only requiring redecoration 

​0 - Hairline cracks less than 0.1mm. 

​No action required. Hairline cracks are classed as negligible. 

1 - Fine cracks of up to 1mm. 

​Fine cracks can be treated easily using normal decoration. Damage generally restricted to internal wall finishes; cracks rarely visible in external brickwork. 

2 - Crack widths up to 5mm. 

Cracks easily filled. Recurrent cracks can be masked by suitable linings.

​Cracks not necessarily visible externally; some external repointing may be required to ensure weather-tightness. Doors and windows may stick slightly and require easing and adjusting. 

Serviceability - Affecting weather-tightness or operation of door and windows 

3 - Crack widths of 5 to 15mm (or several of e.g. 3mm). 

Cracks that require some opening up and can be patched by a mason. Repointing of external brickwork and possibly a small around of brickwork to be replaced.

​Doors and windows sticking. Service pipes may fracture. Weather-tightness often impaired. 

4 - Extensive damage, cracks 15 to 25mm. 

Extensive damage which requires breaking-out and replacing sections of walls, especially over doors and windows.

​Windows and door frames distorted, floor sloping noticeably. Walls leaning or bulging noticeably, some loss of bearing in beams. Service pipes disrupted. Typical crack widths are 15 to 25mm, but also depends on the number of cracks. 

​Stability - Requiring structural intervention 

5 - Structural damage, cracks greater than 25mm. 

Structural damage that requires a major repair job, involving partial or complete rebuilding.

Beams lose bearing, walls lean badly and require shoring. Windows broken with distortion. Danger of instability. Typical crack widths are greater than 25mm but depends on the number of cracks.

Note - further consideration may be required where cracks are widening over time.