# What is Bulging?
**Bulging is the visible outward deformation or displacement of a wall surface from its original plane. In construction, bulging typically indicates an underlying structural problem — such as excessive lateral pressure, moisture expansion, corrosion of embedded elements, or loss of bond between wall layers — that requires investigation and repair.**
## Causes of bulging
### Lateral pressure
Retaining walls and basement walls can bulge when earth or water pressure exceeds the wall’s designed resistance. This is common in older structures where drainage behind the wall has failed.
### Moisture and thermal expansion
Brickwork and blockwork expand when absorbing moisture or heat. If expansion joints are absent or insufficient, the accumulated movement forces the wall outward.
### Corrosion of embedded steel
When steel lintels, ties, or reinforcement within masonry corrode, the rust occupies several times the volume of the original steel, generating internal pressure that pushes the outer leaf outward.
### Cavity wall tie failure
In cavity walls, corroded or broken wall ties can allow the outer leaf to separate from the inner leaf, leading to localised or widespread bulging.
### Foundation settlement
Differential settlement creates uneven stresses in walls, which may manifest as bulging combined with cracking.
## Assessment methods
– Visual inspection and measurement with a straightedge or laser level
– Monitoring over time using crack gauges or tell-tales
– Structural survey by a qualified engineer
– Endoscope inspection of cavity conditions
## Remedial options
– Rebuilding the affected section
– Installing new wall ties (helical or resin-bonded)
– Relieving lateral pressure through improved drainage
– Structural stitching with stainless steel bars
## Applications
– Structural surveys of historic and ageing buildings
– Condition assessment of retaining walls
– Maintenance inspection of cavity wall construction
– Diagnosis of facade defects in renovation projects
## Related terms
– Wall tie failure
– Lateral restraint
– Expansion joint
– Structural cracking
– Pointing and repointing
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