Cracking

Question 1

What guidance is there covering cracking?

Answer 1

BRE 251

Question 2

What are categories of cracking and which document outlines them?

Answer 2

BRE 251

0 - Hairline (0.1mm)
1 - Fine (1mm)
2 - Easily filled (5mm)
3 - Require opening up and patching (5-15mm)
4  - Extensive Damage (15-25mm)
5 - Structural damage (25mm+)

Question 3

What are common causes of cracking ?

Answer 3

Differential thermal movement

Corrosion and decay (cavity wall tie failure)

Poor design detail or workmanship (failing lintels or DPC)

Settlement

Subsidence or heave

lack lateral restraint

failing lintels (not enough end bearing)

Question 4

What causes of cracking are associated with the ground?

Answer 4

Shrinkage and heave caused by clay soils in proximity to trees.

Settlement

Movement due to poor ground of mining subsidence

Nearby excavation

Soil erosion - particularly in silty/san soils caused by leaking pipe

Chemical attack - sulphates in ground attacking foundations.