Building Pathology L2 The Birches / 2 Storey Detached Block

Question 1

Explain how you investigated this defect.

Answer 1

I inspected the external wall where the bulge was evident. I checked the vertical levels with a 1200mm spirit level. I measured the bulge using a steel tape measure.

I produced a sketch noting the location of the bulge, chimney, floor level (approx) and measurements.

I looked for evidence of cracks, particularly horizontal cracks, every 4 or 5 courses. There was evidence of the wall being pointed within the last 1 to 2 years.

I inspected the internal walls and chimney on the ground and first floor, checking for visual signs such as cracks and checking the vertical levels.

Question 2

Describe the defects you saw to the external wall.

Answer 2

Bulge was clearly visible.
Slight undulations on the wall in general, had reasonable vertical alignment
No obvious cracks (evidence of walls being repointed)

Question 3

Outline the dimensions of the bulging brickwork – how did you measure this to include a measurement in your report?

Answer 3

The face of the wall affected by the bulge measured approximately 3m wide x 1.5 to 2m high. I used a steel tape measure

Question 4

What evidence was there to suspect cavity wall tie failure?

Answer 4

Wall was bulging
Although there was no sign of cracking between mortar joints, the wall showed evidence of repointing, which may have masked any cracks
Wall tie failure is a relatively common defect with the age of the property
The bulge in close proximity to the flue of the internal fireplace (affected by flue)

Question 5

Other than a borescope what other methods of invasive investigation could you have instructed?

Answer 5

Removal of brick to gain view in the cavity. Removal of mortar around the wall tie(s) to inspect for corrosion and delamination of ties.

Question 6

Explain the remedial repairs you recommended to the client?

Answer 6

1. Take down the section where it bowed and rebuild
2. The wall ties should have a maximum horizontal spacing of 900mm and a vertical spacing of 450mm, or not less than 2.5 ties/m2 (Approved Document A)
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