Cracking

Question 1

What BRE document assesses cracking in buildings.

Answer 1

BRE 251

Question 2

What are the different levels of cracking in buildings (BRE 251):

Answer 2

0 - Hairline cracks less than 0.1mm.
1 - Fine cracks of up to 1mm.
2 - Crack widths up to 5mm.
3 - Crack widths of 5 to 15mm (or several of e.g. 3mm).
4 - Extensive damage, cracks 15 to 25mm.
5 - Structural damage, cracks greater than 25mm.

Question 3

What are the signs of wall tie failure?

Answer 3

• Horizontal cracking.
• Cracking at regular intervals. (450x900mm)
• Random bulges in brickwork
• Rust staining

Question 4

What are the spacings for wall ties?

Answer 4

What are the spacings for wall ties?

Question 5

What is wall tie failure?

Answer 5

Corrosion of existing wall ties, or insufficient spacing or incorrect wall ties have been used.

Corrosion causes expansion.

Question 6

What are some historic materials used for wall ties?

Answer 6

• Iron
• Steel with a zinc coating
• 1981 - built before then, to play close attention.
  They changed the building regs as the wall ties were updated to stainless steel or plastic.

Question 7

How would you identify wall tie failure?

Answer 7

• Regular cracking to brickwork
• Bowing of outer leaf.

Question 8

How would you remedy wall tie failure?

Answer 8

Physical insertion:
- Mechnancial
- Helical tie