Construction practice for a house extension

Building work must be sequenced so that each part of the air barrier is completed before following trades cover the work. The ‘out of sight – out of mind’ approach will not achieve airtightness: a subsequent pressure test will show up any inadequacies.

It is important to recognise that the test simply shows the overall airtightness, with a subsequent air leakage audit being needed to identify significant leakage paths. This can prove very disruptive, time consuming and costly once the air barrier has been concealed. It is therefore extremely important to ‘build tight, first time, every time’.

The following trades must not compromise the air barrier by accidentally damaging it, or even deliberately penetrating it in order to complete their work. If additional service penetrations are needed after the air barrier has been completed, the damage caused to the barrier must be repaired. These repairs must be made before the air barrier is concealed.