Air tightness compliance is basically the evidence that your build meets the heat-loss and energy-efficiency rules set out in Part L Building Regulations.

To prove that, every new build or retrofit needs an air tightness test — you might also hear it called an air permeability test, an air pressure test, or simply pressure testing.

Once the test is done, the important bit is the certificate. That’s the document Building Control actually look at when deciding if your project is compliant.

Your certificate shows:

• The building has been properly pressure tested
• The air permeability score meets the limits in Approved Document L
• The testing method meets the required standards (BS EN 13829 or ISO 9972)
• The results are accurate, traceable and acceptable for sign-off

So the test measures the leakage, the certificate proves the result, and that proof is what gets you through Part L.

When we’re finished, you get everything you need in one place — your official air tightness certificate, the test data, the method used, the equipment details, plus any practical steps to fix things if your build needs a quick tweak before re-testing.

It’s all the paperwork Building Control expect, without the headache.

Part L deadlines creep up fast, and when you’re trying to keep a build on schedule, the last thing you need is a hold-up because the paperwork isn’t right. We work with the people who feel that pressure day to day.

We help:

Builders and site managers

Keeping plots moving, avoiding failed inspections and getting airtightness certified without stopping everything else on site. This includes support when you need a building air tightness test repeated or backed up with the correct certification.

Developers

Especially those with multiple units going through sign-off at the same time. Whether it’s a new build air test or sorting documentation across several plots, we handle the testing and certification so you can hand over properties without last-minute delays.

Contractors who’ve had a fail and need clear next steps

We explain what went wrong, what needs fixing and how to get a pass without endless back-and-forth.

If you’re getting organised early or dealing with a last-minute scramble to meet Part L, we’ll get the airtightness testing and paperwork boxed off so you can crack on without delays.

And if you need ventilation certification and compliance alongside your airtightness testing, we can take care of that too.

Why Part L Air Tightness Compliance Matters for Your Project

Air tightness doesn’t feel important until it causes a delay — and then it becomes the only thing anyone talks about. A poor score or missing certificate can stall sign-off, push back handovers and throw the whole build schedule out.

Getting it right makes everything smoother. Here’s what proper air tightness certification actually prevents on site:

Handover delays: With a compliant air permeability score and the right paperwork, Building Control can sign off Part L without extra visits or questions.

Repeat call-outs and rework: A clear certificate backed by accurate testing means you’re not calling trades back in to hunt for leaks at the last minute.

Unnecessary costs: Failed tests, extra labour, wasted time — it all adds up. Certification that’s done properly avoids all of that.

Poor EPC ratings and heat-loss issues: Leaky buildings cost more to run, and buyers notice. A passed air tightness test protects the energy performance of the property.

Stress for your team and your clients: Good certification takes the pressure off. The results are clear, the expectations are clear and everyone knows exactly where they stand.

When your air tightness testing and documentation are sorted, Part L Building Regs become one less thing to worry about — and your project stays on track.

Why Choose AVT UK for Part L Air Tightness Certification & Compliance?

AVT isn’t just a testing service — we’re the people you call when you want the paperwork sorted properly and the job done without drama.

• We keep your build moving -Reports land quickly, certificates are issued promptly, and we make sure nothing idles on your desk waiting for sign-off.

• We know Part L inside out – Our team tests and certifies hundreds of properties a year. New builds, retrofits, extensions — whatever you’re working on, we’ve seen it, tested it and got it over the line. And if you’re working on a retrofit project, our airtightness certification supports PAS2035 compliance pathway too.

• We communicate like real humans – You won’t get jargon, long delays or vague answers. You’ll get straight, practical guidance you can actually use on site.

• We help you avoid repeat tests – If something needs adjusting, we’ll tell you exactly what to fix and how. No guesswork. No wasting days calling trades back in.

• Building Control trusts our documentation – Our certificates are clear, accurate and recognised. You won’t find yourself stuck in a loop of questions or requests for extra information.

• We’re reliable, responsive and easy to work with – From one-off homeowners to developers with multiple plots, we’re set up to handle urgent requests, tight deadlines and busy build schedules.

When you bring us in, you’re not just getting an air tightness certificate — you’re getting someone in your corner making sure Part L doesn’t derail your timeline.