Cracks

Question 1

Where would you find information about cracking?

Answer 1

BRE Digest 251
BRE Digest 475

Question 2

How many categories of cracking are there as listed in BRE Digest 251?

Answer 2

6

Question 3

What is defined as a category 0 crack according to BRE Digest 251?

Answer 3

Hairline cracks of less than about 0.1mm which are classed as negligible.
No action required.

Question 4

What is defined as a category 1 crack according to BRE Digest 251?

Answer 4

Fine Cracks which can be treated easily using normal decoration.
Damage generally restricted to internal wall finishes, cracks rarely visible in external brickwork.
Typical crack widths up to 1mm.

Question 5

What is defined as a category 2 crack according to BRE Digest 251?

Answer 5

Cracks easily filled.
Recurrent cracks can be masked by suitable linings.
Cracks not necessarily visible externally; some external repointing may be require to ensure weather- tightness. Doors and windows may stick slightly and require easing and adjusting.
Typical crack widths up to 5mm.

Question 6

What is defined as a category 3 crack according to BRE Digest 251?

Answer 6

Cracks which require some opening up and can be patched by a mason.
Repointing of external brickwork and possibly a small amount of brickwork to be replaces.
Doors and windows sticking.
Services pipes may fracture.
Weather tightness often impaired.
Typical crack widths are 5 – 15 mm or several of say, 3mm.

Question 7

What is defined as a category 4 crack according to BRE Digest 251?

Answer 7

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 15-25mm but also depends on number of cracks.

Question 8

What is defined as a category 5 crack according to BRE Digest 251?

Answer 8

Structural damage which 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 number of cracks.