Preparing a building properly prior to an air tightness test, is essential to achieving a compliant test result. Even small gaps, unsealed penetrations or incomplete finishes can significantly increase air leakage, leading to failed tests, costly delays and remedial works. By ensuring the building is suitably complete, weather‑tight and sealed in accordance with design intent, contractors can minimise risk, streamline the testing process and give the project the best chance of meeting its required air permeability target under Approved Document L.As a UKAS & ATTMA Level 2 accredited air testing company, we have undertaken thousands of air tightness tests over the last 20 years and despite an overall improvement most air tightness results, there is still room for improvement. So, how do you best prepare your building for an air tightness test?
Preparing your Building for an air tightness test
With this in-mind we have written the following article to help clients prepare for their air tightness test. There are literally hundreds of areas that need to be considered when trying to create an airtight building – the main areas are:
- The building fabric: the building fabric accounts for the walls, floor and roof. The type of build will dictate the amount of extra ‘onsite’ sealing works that may be required. For instance, it’s usually easier building with timber frame, than with masonry.
- Wall/floor/ceiling junctions: It is usually the wall/floor junction around skirting boards, and the wall/roof junctions by the eaves where the problems are usually worst.
- Doors and windows: doors and windows are often some of the worst areas of air leakage within a building fabric. Where the frame meets the wall reveal, is usually down to site detailing, but how the window or door closes against the frame is down to the window/door manufacturer and their installers. Sash windows or sliding patio doors can be susceptible to air leakage even if they are working properly. Twisted frames, missing seals and poorly (loosely) adjusted latches, are just a few issues that we find during smoke testing.
- M&E Service penetrations: service penetrations through the building envelope to allow for cables, pipes and ductwork are also a main area of air leakage. They’re not difficult to deal with if tackled at the right juncture i.e., before kitchen units are installed, and it is largely a matter of site supervision that they found and dealt with by a dedicated sealing team of an air tightness champion.
- Internal pocket doors – internal pocket doors, such as the type installed between living/dining rooms and bathrooms, can be a massive area of air leakage, so it’s really important that the builder builds an airtight pocket (sleeve) for the door prior to installing the running gear for the doors, and finally boxing out.
- Recessed ceiling lights – recessed ceiling lights in kitchens/living rooms etc. can also be large area of air leakage. In some large living areas, we have counted over 100 ceiling lights, with each light leaking the accumulated air loss can be huge. Many manufacturers provide airtight (fireproof) socks that go over the light housing (within the ceiling void) which can be an effective solution.
- Ceiling hatches – ceiling hatches, can also leak large amounts of air. Some manufactures offer proprietary door and frame systems, which are easier to install and will further reduce air leakage.
- Loft cupboards – the areas behind loft cupboards doors are often unsealed, sometimes there isn’t even flooring installed. it is essential that the walls ceiling and floors are completely finished, and the cupboard door are fully sealed with good quality seals.
At the start of your design and build process, your architect should be specifying what needs to be done in regard to air tightness, and the importance of having an air tightness champion on site to reduce the chance of an air tightness test failure.
We can help your Building pass an air tightness test
We work with our customers throughout their design and construction stages, we can provide advice and guidance on the most feasible ways to avoid air leakage and pass your air tightness test. we have also written the following air tightness checklist to help clients prepare for their testing.
We can provide general air leakage design advice for your building envelope and onsite guidance. Upon completion of your project, we provide Nationwide UKAS Accredited Tightness Testing for domestic and commercial buildings to help you demonstrate Building Regulation Part L Compliance.
To find out more about our air tightness testing service or if you wish to discuss your project, please contact us by email at info@aptoundtesting.co.uk
Accreditations & Technical Competence for Air Tightness Testing
APT Sound Testing is a UKAS‑accredited ISO/IEC 17025 testing laboratory specialising in on‑site (field) air tightness testing for commercial and large‑scale buildings. Our accreditation demonstrates that all testing, reporting and quality processes meet the highest technical and procedural standards recognised in the UK.
We are an ATTMA Level 2 registered organisation, qualified to test Large, Complicated and High‑Rise (LCHR) buildings, as well as phased and zonal hand‑over projects. In addition, we are ATTMA EA accredited, enabling us to produce accurate and compliant envelope area calculations for complex commercial structures.
With over 20 years of specialist experience, using the latest high-power UKAS calibrated Retrotec blower door equipment, our engineers have delivered testing and consultancy on some of the UK’s most prestigious and technically challenging developments, including Battersea Power Station and the Imperial War Museum London.
Our combination of accredited competence, deep technical expertise, and long‑standing industry experience ensures that every project receives reliable, repeatable and fully compliant air tightness testing to the highest professional standard.
📞 Contact Us Today
If you want to avoid costly failures and ensure your commercial building passes its air test first time, our expert team is ready to help. Please contact Darren on 07775623464 or email us at info@aptsoundtesting.co.uk