Category of damage

Degree of damage

Description of typical damage [ease of repair]

Approximate crack width
[mm]

0

Negligible

Hairline cracks of less than about 0.1 mm width are classified as negligible

Up to 0.1 mm

1

Very slight

Fine cracks which can easily be treated during normal decoration. Perhaps isolated slight fracturing in building. Cracks rarely visible in external brickwork

Up to 1 mm

2

Slight

Cracks easily filled. Re-decoration probably required. 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.

Up to 5 mm

3

Moderate

The cracks require some opening up and can be patched by a mason. Repointing of external brickwork and possibly a small amount of brickwork to be replaced. Doors and windows sticking. Sertvice pipes may fracture. Weather tightness often impaired.

5 to 15 mm
[or a number of cracks up to 3]

4

Severe

Extensive repair work involving 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.

15-25 mm but also depends on number of cracks

5

Very severe

This requires a major repair job involving partial or complete re-building. Beams lose bearing, walls lean badly and require shoring. Windows broken with distortion. Danger of instability

Usually greater than 25 mm but depends on number of cracks.

Notes:

in asserting the degree of damage account must be taken of the location in the building or structure where it occurs, and also of the function of the building or structure. Crack width is one factor in assessing category of damage and should not be used on its own as a direct measure of it. Local deviation of slope, from the horizontal or vertical, of more than 1:100 will normally be clearly visible. Overall deviations of 1:150 are undesirable.

References

BRED, 1981, Assessment of damage in low-rise buildings with particular reference to progressive foundation movement, UK Building Research Establishment Digest, 251, 8p.