Full extraction means every external wall of the house cleared back to an empty cavity. It is the right job when the borescope shows wet or slumped material on more than one elevation, when the house sits on an exposed site where the insulation should never have gone in, or when foam has been used and there is no sensible way to take out half of it.
When we recommend a full extraction
We do not recommend clearing a whole house on the strength of one damp patch. The survey decides it.
- the borescope finds saturated or compacted fill on two or more elevations, not just the weather side
- the insulation is urea formaldehyde foam that has shrunk and cracked, or polyurethane foam bonded to both leaves, where partial removal leaves the problem in the wall
- the cavity is narrower than 50mm, which the Building Research Establishment describes as a hollow wall rather than a true cavity and generally unsuitable for retrofit fill
- the house is on a site that Approved Document C would class as severe or very severe exposure to driving rain, and the wall is fair-faced brick with a filled cavity, which is the combination the guidance restricts
How the material comes out
The method is the one used across the trade. It is noisy, and it does not harm the wall. Every job runs through the same nine steps.
- Inspection. We confirm the insulation needs to come out and assess the cavity.
- The original injection holes. We locate the holes the installer drilled near the top of the wall and reopen them.
- Compressed air. Air goes in through the upper holes to loosen the old fill and move it down the cavity.
- Bottom access. Selected bricks come out at the base of the wall to make extraction points.
- Vacuum extraction. A high powered industrial vacuum draws the old insulation out of the cavity.
- Clear and checked. We check the cavity is clear, and confirm with you whether it is being refilled or left clear.
- Thermal bead in, if you want it. Most customers have the cavity refilled with the thermal bead system. If you would rather leave it clear, or the survey says it should stay clear, it stays clear.
- Brickwork reinstated. The removed bricks go back and the affected areas are made good.
- The drill holes. The original holes are filled and colour matched to the wall.
The bricks that come out go back in, bedded and pointed in a mortar mixed to match the existing joints as closely as the wall allows. Injection holes that were poorly filled first time round get repointed while we are at them.
Checking the cavity is clear
An empty-looking extraction point does not mean an empty cavity. Wool bridges on wall ties, bead sits in the corners around window reveals, and foam clings to the inner leaf.
How long it takes and what to expect
Published guides put a typical three-bedroom semi at three to four days of work, a mid terrace at two to three, and a larger detached house at up to a week. Ours vary with the material and the state of the wall, and the quote gives you the price for your house rather than a generic one.
If you think your whole house is in this position, the free survey is where it starts. We look at every elevation, tell you in writing which ones need clearing, and quote for that and nothing more.
Book a free survey and we will tell you what your wall needs and what it costs.
