A cavity is meant to be a gap. Water that gets through the outer leaf runs down the inside of it and out through weep holes or the base.
What is usually in a cavity
- Mortar droppings sitting on wall ties and piled at the base
- Broken bricks, block offcuts and packaging left during construction
- Insulation left behind by a previous extraction, especially wool caught on ties and bead in the corners
- Bead that has migrated from a neighbour’s cavity through a shared party wall gap
- Blocked or missing weep holes, so the cavity cannot drain
- Sleeves missing behind airbricks, so fill has blocked the sub-floor ventilation
How the inspection is done
A borescope is a camera on a flexible probe. We drill 10mm holes in the mortar joint, not the brick, at low and high level on each elevation and at the points where damp shows inside, and look.
Clearing what we find
Debris at the base comes out through the same extraction points used for insulation: a brick removed at intervals along the bottom course, compressed air to loosen, industrial vacuum to remove. Ties fouled with mortar get cleaned where the probe can reach; a tie that is rusted through is a different job and we say so.
When a clean is enough
Many damp problems blamed on cavity wall insulation are really debris, a blocked weep hole or a cavity tray that was never fitted over a lintel. If the borescope shows sound, dry fill and a bridged base, the clean is the job and the fill stays.
If you would rather know what is in your walls before you decide anything, that is what the free survey is for. Book a free survey.
