England & Wales

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

• Approved Document L1A: (applicable to new dwellings)
• Approved Document L2A: (applicable to new non-dwellings)
• Approved Document L2B: (applicable to large extensions to non-dwellings)

Testing Requirements – Dwellings

Section 3.17 reads:

“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 3.18 states:

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

Section 3.18 goes on to say:

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

Section 3.21 reads:

“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.”

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 of the person carrying out the pressure testing.

To be classed as 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.”