CAVITY WALLS Published January 12, 2025 15 min read

The Great Cavity Wall Crisis: Why Properties Built 1920-1990 Are at Risk

Millions of UK homes built between 1920-1990 with cavity wall insulation are experiencing severe damp problems. Government-backed schemes promoted cavity wall insulation without fully understanding the long-term consequences. Here's why your property might be affected and what you can do about it.

Expert Team

By the Expert Team at Damp Solutions Direct

Cavity wall insulation specialists with over 20 years experience

The Scale of the Crisis

6.5M+

Properties affected nationwide

£15bn

Estimated repair costs

78%

Of 1960s-1980s properties at risk

Critical: If your property was built between 1920-1990 and has cavity wall insulation installed after 1970, you're likely affected by this crisis.

Understanding Cavity Wall Construction

Cavity walls became the standard construction method in the UK from the 1920s onwards. They consist of two separate walls (inner and outer leaves) with a gap (cavity) between them, designed to prevent moisture from penetrating to the inside of the property.

Construction Periods

  • 1920-1945 Early cavity walls, 50-75mm cavity, mainly unfilled
  • 1945-1970 Standard cavity construction, 75-100mm cavity, unfilled
  • 1970-1990 Modern cavity walls, insulation retrofitting begins

Original Design Purpose

  • Prevent moisture penetration from outer wall to inner wall
  • Allow air circulation to dry out any moisture
  • Provide thermal barrier (air gap insulation)
  • Enable weep holes to drain trapped water

The Government-Backed Insulation Push (1970s-2010s)

Following the oil crisis of the 1970s, the UK government launched aggressive energy efficiency campaigns. Cavity wall insulation was promoted as a simple, cost-effective solution to reduce heating costs and carbon emissions.

Government Schemes That Promoted Cavity Wall Insulation

1970s-1980s:

  • • Home Insulation Scheme
  • • Energy Efficiency Grants
  • • Local Authority Schemes
  • • British Gas Promotions

2000s-2010s:

  • • Carbon Emissions Reduction Target (CERT)
  • • Community Energy Saving Programme (CESP)
  • • Energy Company Obligation (ECO)
  • • Green Deal (2013-2015)

The Fundamental Problem

These schemes promoted cavity wall insulation without adequate assessment of exposure conditions, building suitability, or long-term consequences. The focus was on quantity over quality, leading to inappropriate installations that are now causing widespread damp problems.

Why Cavity Wall Insulation Causes Damp Problems

The theory behind cavity wall insulation was sound, but the reality of UK weather conditions, building quality, and installation practices has created a perfect storm for damp problems.

The Moisture Bridge Problem

How It Should Work:

  • Rain hits outer wall
  • Moisture stays in outer leaf
  • Air gap prevents transfer
  • Moisture drains away

What Actually Happens:

  • Insulation creates moisture bridge
  • Water travels through insulation
  • Moisture reaches inner wall
  • Damp appears inside property

Location Factors

  • • Exposed coastal areas
  • • Properties facing prevailing wind
  • • Areas with high rainfall
  • • Properties on hills or exposed locations
  • • Urban areas with driving rain

Installation Issues

  • • Poor quality installation
  • • Wrong insulation type for conditions
  • • Inadequate pre-installation survey
  • • Blocked or missing weep holes
  • • Overfilled cavities

Building Issues

  • • Cracked pointing or rendering
  • • Faulty gutters or downpipes
  • • Missing roof tiles
  • • Poor window seals
  • • Structural movement

Warning Signs Your Property Is Affected

Immediate Red Flags

  • Damp patches appearing on internal walls, especially after heavy rain
  • Musty smell in bedrooms or living rooms
  • Wallpaper peeling or paint bubbling
  • Black mould appearing on walls or ceilings
  • Cold spots on internal walls
  • Higher than normal humidity levels
  • Efflorescence (white powdery deposits) on walls
  • Increased condensation on windows

Risk Assessment Questions

Answer these questions to assess your property's risk level:

Building History:

  • ✓ Was your property built 1920-1990?
  • ✓ Was cavity wall insulation installed after 1970?
  • ✓ Was it installed through a government scheme?
  • ✓ Do you have the installation guarantee/certificate?

Location Factors:

  • ✓ Is your property in an exposed location?
  • ✓ Do you face the prevailing wind direction?
  • ✓ Are you within 5 miles of the coast?
  • ✓ Is your area prone to driving rain?

If you answered YES to 3 or more questions, your property is at high risk and should be professionally assessed immediately.

Don't Let Cavity Wall Problems Damage Your Home

Get a professional cavity wall inspection to identify problems before they become expensive disasters. Our certified specialists provide comprehensive assessments and effective solutions.