Cavity Wall Insulation Problems: Damp & Removal Guide

What is Cavity Wall Insulation?

Cavity wall insulation involves filling the gap (cavity) between the inner and outer walls of a property with insulating material. Common materials include:

• Mineral wool
• Polystyrene beads
• Polyurethane foam
• Recycled newspaper (cellulose)

Common Cavity Wall Problems

1. Damp Penetration

The cavity normally acts as a barrier preventing rain from reaching internal walls. Insulation can bridge this gap, allowing moisture to travel across:

• Cold spots on interior walls
• Damp patches appearing after rain
• Mould growth on affected walls
• Peeling wallpaper or paint

2. Unsuitable Properties

Not all properties are suitable for cavity wall insulation:

• Exposed locations: Properties facing prevailing wind and rain
• Narrow cavities: Less than 50mm wide
• Cracked walls: Existing structural issues
• Porous bricks: Soft or damaged brickwork
• No cavity: Solid wall properties (common mistake)

3. Installation Issues

• Incomplete filling leaving cold spots
• Material slumping over time
• Blocked cavity ventilation
• Damage to existing wall ties
• Debris left in cavity

Signs Your Cavity Wall Insulation is Failing

1. New damp problems: Appearing after installation
2. Cold patches: Areas colder than rest of wall
3. Mould growth: Especially in corners
4. Condensation: Increased moisture on walls
5. Musty odors: From trapped moisture
6. Staining: Brown or yellow marks on walls
7. Efflorescence: White salt deposits on brickwork

CIGA Guarantee

Most cavity wall insulation installations are covered by a 25-year CIGA (Cavity Insulation Guarantee Agency) guarantee:

• Check if your installer was CIGA registered
• Guarantee covers installation defects
• Free remedial work if installation at fault
• Contact CIGA directly if installer unresponsive

Cavity Wall Extraction

If problems persist, extraction may be necessary:

Extraction Process

1. Survey: Borescope inspection to confirm insulation present
2. Extraction: Vacuum system removes material through drilled holes
3. Verification: Further inspection to ensure complete removal
4. Repair: Holes made good and repointed

Extraction Costs

• Survey: £200 - £400
• Extraction (small property): £1,500 - £2,500
• Extraction (medium property): £2,500 - £4,000
• Extraction (large property): £4,000 - £6,000
• Repointing: £500 - £1,500

When Extraction May Not Work

Some materials are harder to extract:

• Foam: Often impossible to fully remove
• Bonded materials: Stuck to cavity walls
• Wet insulation: Becomes compacted

Alternative Solutions

If extraction isn't possible or practical:

• External render: Creates weather barrier
• Internal wall lining: Adds insulation internally
• Improved ventilation: May reduce condensation
• Damp-proof course: If DPC is the issue

Preventing Cavity Wall Problems

Before installation:

• Get independent survey to check suitability
• Ensure installer is CIGA registered
• Check cavity width (minimum 50mm recommended)
• Assess property exposure to weather
• Inspect existing wall condition

Compensation Claims

You may claim compensation from:

• CIGA: If installation defective
• Installer: Poor workmanship or wrong advice
• Government scheme: If installed under ECO/GBIS