Across the thousands of air tightness tests we run each year, the same handful of issues come up again and again. Knowing what to look for before the engineer arrives can be the difference between a first-time pass and a callout fee.
Domestic — common faults
- Unsealed loft hatches — fit draft excluders or compriband seals.
- Service penetrations — pipework, cable trays and waste pipes through external walls and ceilings often leak. Use intumescent sealant or air-tightness grommets.
- Skirting board gaps — caulk top and bottom; if no skirting (behind kitchen units, baths) seal floor-to-plasterboard with expanding foam.
- Socket and switch boxes on external walls — back-box sealing is essential; consider air-tight back boxes on cold walls.
- Soil vent pipes — check the seal where the SVP exits the roof; this is a frequent source of large leaks.
- Integral garage doors — fit perimeter brush seals.
- Trickle vents and intermittent extracts — must be in place and closeable; the engineer will tape them up for the test.
Commercial — common faults
- Curtain wall and cladding junctions — particularly at heads, sills and corner returns. Specify and inspect tape and gasket continuity.
- Service risers — vertical risers between floors are a major leakage path; seal at every floor penetration.
- Roller shutter doors — a known weak point. Brush seals and bottom seals must be intact.
- Plant room and ductwork penetrations — often left unsealed during commissioning. Check before the test.
- Suspended ceilings — voids above suspended ceilings can communicate with the riser; seal the perimeter at the wall-ceiling junction.
Cross-cutting issues
- Test rig location — choose a doorway that’s easy to seal. The engineer needs at least one standard-sized door for the fan.
- Site activity — windows opened by other trades during the test will fail it. Brief the team in advance.
If you’d like UKBC engineers to walk a site pre-test and flag likely issues, we offer a pre-test inspection service that pays for itself by catching problems before the formal test.