England and Wales - Building Regulations

This page was last updated September 2023

Building Regulations for England and Wales, through the Approved Document Part L (‘Conservation of Heat & Power’), stipulate the air tightness testing of buildings. Currently, this requirement exists in the three of the four Part L Approved Documents:

Approved Document L1A

Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments

Applicable to new dwellings

Approved Document L2

Approved Document L, Conservation of fuel and power, Volume 2: Buildings other than dwellings, 2021 edition incorporating 2023 amendments

Applicable to new non-dwellings and large extensions to non-dwellings. Contains L2A and L2B

Testing Requirements - Dwellings

On each development, an air pressure test should be carried out on three units of each dwelling type or 50 per cent of all instances of that dwelling type, whichever is the less. For the purposes of Approved Document L1A, a block of flats should be treated as a separate development, irrespective of the number of blocks on the site. The dwelling(s) to be tested should be taken from the first completed batch of units of each dwelling type

Section 3.17

The specific dwellings making up the test sample should be selected by the Building Control Body in consultation with the pressure tester......

.....The results of all tests on dwellings in the sample should be reported to the Building Control Body, including any test failures

Section 3.18

When a dwelling fails the initial pressure test, other dwellings of the same dwelling type that have not been tested should be examined and, where appropriate, remedial measures applied

Section 3.21

Dwelling Types

Approved Document L1A is very specific about what a ‘dwelling type’ is.

Appendix A states:
“Dwelling type is the particular group allocated to each dwelling on a development to provide the basis for assessing the pressure testing regime. The allocation of each dwelling to a dwelling type should be the responsibility to the person carrying out the pressure testing.”

To be classed as a of the same type, dwellings should:

  1. be of the same generic form (i.e. detached, semi-detached, end-terrace, mid-terrace, ground-floor flat (including ground-floor maisonette), mid-floor flat (including top-floor maisonette);
  2. include the same number of storeys;
  3. have the same design air permeability
  4. have similar adjacency to unheated spaces such as stairwells, integral garages etc.
  5. have the same principal construction details;
  6. have a similar (i.e. plus or minus 1) number of penetrations, i.e. for windows, doors, flues/chimneys, supply/exhaust terminals, waste water pipes;
  7. have envelope areas that do not differ by more than 10 per cent.”