Air Tightness Testing for Part L Compliance

Need to get your flats and houses signed off by Building Control?

Trust an established, Constructionline Gold company to provide air tightness testing and documentation.

Air Leakage Testing helps you to prove that your new build dwellings meet Approved Document L1A of the Building Regulations.

We are registered with the Air Tightness Testing Measurement Association (ATTMA) and our engineers have decades of experience.

On larger developments, multiple air tightness tests can be carried out in a single visit. We are equipped to undertake Air, Sound and Ventilation testing at the same time –  less disruption and lower costs.

Air Leakage Testing Reading
Air Leakage Testing Reading
Air Leakage Testing Reading

Need a quick turnaround?

We take pride in offering quality and speed at competitive rates. From the initial enquiry, we can arrange a date for air tightness testing within a week. Certificates can be issued on the next working day.


Our test engineers are based across the South East, so are conveniently located to work with builders and developers across the Home Counties and London. Let us help you to get your properties on the market.

Need Technical Advice on Air Testing?

If you are seeking high levels of air tightness, Air Leakage Testing also offers design reviews, pre-test inspections, sample/benchmark testing and toolbox talks. Our technical advice at the design and early construction phases can improve the chances of air tightness compliance.


Whatever the project and target, we aim to guide you through the process to identify potential issues ahead of testing and ensure the timing of the test is correct. These measures minimise the risk of failure and make things as stress-free as possible.

What if a Building Fails an Air Tightness Test?

If a property fails to meet the Air Tightness required by Approved Document L1A/the SAP assessment, our test engineers will identify the air infiltration paths while on site.


With a clear diagnosis and our expertise, it is possible to identify solutions. Re-testing can be arranged when the issue has been addressed, in the majority of cases, this is during the same site visit.

Get a Quote

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We won’t be beaten on price!


How it works

  1. We provide a quote based on the size of the building and location – it is usually helpful to have PDF Plans to calculate the size of larger buildings
  2. We provide a checklist and agree a date
  3. We call you ahead of the test date to talk you through the preparation and process and agree the timings. We would also look to confirm the air permeability that has been targeted in the energy model at this stage, if it hasn’t been discussed already. The results of the test are a key component of the calculation of the overall energy efficiency of the building and, therefore, achieving the necessary air tightness is a critical part of building control sign-off.
  4. On houses and flats we would typically complete the temporary sealing for the test when we arrive on site. For larger buildings, we would talk you through what would need to be done in advance of our arrival.
  5. We conduct the test. Testing is done through a pressure test whereby fans are installed into a doorway of the building and used to create a measurable difference between the pressure inside and outside of the building. The amount of air needed to maintain this difference can be used to indicate the volume of air escaping through the fabric (what would be draughts in the building’s day-to-day life).
  6. If the building doesn’t achieve its target at the first time of asking, we can use our equipment to identify the leakage paths. If these can be addressed relatively quickly, then we can repeat the test on the same day. In order to achieve increasingly challenging energy performance targets, air tightness requirements are becoming tighter. Typically, a good level of air tightness can still be achieved with excellent attention to detail in the decorative finish but, to achieve tighter targets, consideration must be given to air permeability within the design of the fabric, including use of membranes and tapes to maintain the air barrier.

Why use ALT?

  • Helpful – we work with you to achieve the best result, identifying potential issues and repeating the testing once these have been addressed. We are on hand to answer any questions before, during and after the testing
  • Knowledgeable – we have been air testing since 2002 and all our test engineers have a vast amount of experience
  • Flexible – we try to fit in with the dates and times you need the test, we try to work around other trades to minimise disruption on site
  • Responsive – we issue quotes and certificates within 1 working day, our lead-times are typically around a week but we will try and fit you in sooner if required
  • Great value – our prices are very competitive but we can also undertake air and sound testing on the same visit to save you more money. If you do manage to find the testing cheaper, we will beat any quote.


“Air Leakage Testing provided a quick and efficient service. Their technical knowledge helped us to quickly resolve a minor issue and meet Building Regs requirements.”

Dave Skeet, Thomas Homes

“No queries at all. We would work with ALT again and highly recommend them to others.”

Georgina Scates, Hoopers Homes

01799 540220

Enquire about Air Tightness Testing

Air Leakage Testing Limited

Essex Office (Eastern Counties): 01799 540220
Bucks Office (Western Counties): 01296 791079


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