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10 Reasons for Test Failure | Air Tightness Testing Ltd.

10 Common Reasons for Failing an Air Tightness Test

Air tightness tests aren’t cheap, and can take upwards of two hours out of your day. Failing costs money, and takes up too much time.

But passing doesn’t have to be difficult. Here’s the top 10 reasons for failure, and how you can deal with them.

1. Not knowing what your targets are

Be sure that your Standard Assessment Procedures (SAP) are done to a high standard, and you know what air pressure results you’re looking for in your property.

This can be found on the SAP calculation report, and it might be called the air permeability, DAP or q50 figure.

2. Not knowing when to time it

70% of tests are failed because the test is done too early in the building process.

The earlier you are in the testing process, the less likely you are to pass, purely because there are far more issues with the structure of the building – because construction isn’t complete.

It sounds obvious, but many people just try and get it done early, wasting time and money in the process. Don’t do it. Always wait until you’re ready.

3. Not checking your entrances

Whilst your entrances should be taped over and made ready before the pressure test, you should still pay close attention to them before you sign it off.

It’s also worth noting that you must have one door frame that’s smaller than 2.25m x 1.1m, so the testing fan can be fitted.

4. Not double checking the bathrooms.

Bathrooms are a serious issue when it comes to air leakage, because of the prevalence of pipework. Silicone sealant around any entry point is the easy way to stop this from happening.

You should make sure your bath panels are correctly sealed, as well, before you box anything in.

5. Not sealing your skirting boards

Skirting boards are another overlooked problem when it comes to air leakage. All skirtings should be sealed with a quality silicone sealant, both above and below.

Contrary to what you might think, carpets don’t really prevent air flow, so won’t prevent air loss.

6. Not taking care around Kitchen Appliances

Again, pipework is the key issue here. The best way to avoid unnecessary air leakage is to use your old friend, silicone sealant, around any pipework that travels through any walls.

7. Not paying attention to Loft Hatches and draft excluders

Any area that leads into a roof void, whether that’s a simple loft hatch or another access point, has to be sealed off. Loft hatches are a big deal, because they tend to have a surprising amount of area, so make sure they’re fitted with a quality draft excluder or seal beforehand.

8. Not understanding the different types of properties and why that matters

L1A building regs specify that you have to test at least 50% of each similar dwelling type, or a minimum of 3 of each type, whichever is the smaller figure.

Bear in mind, to be classified as ‘similar,’ these dwellings have to be built in the same way with the same materials, have a floor area difference no greater than 15% from each other, and have no more than one significant opening different in design.

If they do differ, well, that means more tests.

9. Not sealing holes as you go

It’s easy to drill a hole and move on, forgetting about it. However, if you do this just a couple of times, then it could easily contribute to a failure.

Instead, make sure to fill anything that could contribute to airflow as you work. It saves time and effort long term.

10. Not filling around service points and sockets

We’ve saved the best for last.

According to sources in the industry, gaps around sockets and switches should be filled with a jointing compound. But this is pretty much never done.

This is actually one of the largest contributors to heat loss, as it creates a constant chimney effect in the drywall.

It might take some time, but by focusing on the tiny issues such as these, you’re less likely to have them compound into a major problem, and a failure on your test.

iATS Registered and UKAS Recognised


We are registered with iATS (Independent AirTightness Testing Scheme) and use equipment calibrated by UKAS laboratories. Our testing procedures are also recognised by UKAS.