How Much Does an Air Tightness Test Cost?
Air tightness testing: From £95 + VAT (per plot). Guide price. Get a free quote for your project. This guide explains who needs a test, what else to allow for and how to avoid paying for a second visit.
In this guide
Who needs an air tightness test?
Approved Document L says an air pressure test should be carried out on every new home. There is no sampling, so each house and flat gets its own test. The same applies under the new edition that takes effect on 24 March 2027.
New houses and flats
Yes, every one.
New commercial buildings
These are tested too, against the target in the SBEM calculation. See our air tightness testing page for the exception for smaller buildings.
Conversions and extensions
Not usually, though a test can help where the SAP assumed a better figure than the default.
What result do I need?
A new home must be no worse than 8 m³/h·m² at 50 Pa. That is only the legal limit. Your SAP calculation will usually set a tighter target, and that is the figure your test has to meet. Check it early, because a very low target can mean extra work on site.
The measured result then goes into the as-built SAP, which produces the Energy Performance Certificate. If you do not have your SAP yet, see how much SAP calculations cost.
What can add to the cost?
The test fee is rarely the whole story. These are the things that can cost builders more:
- A failed test. If a home misses its target, the air leakage has to be improved and the home retested until it passes. All results, including fails, must be reported to Building Control.
- A home that is not ready. If the tester arrives and doors, windows or seals are not finished, the test may not be able to go ahead.
- Sealing work. Finding and fixing leaks late on means opening up finished work and holding up handover.
- A very tight SAP target. If the result is above the target but below the limit of 8, the SAP can sometimes be rerun with the measured figure. Ask us before you pay for remedial work.
Ask what a retest costs when you get your quote, so there are no surprises.
How to pass first time
We send a site readiness checklist before the visit. The main things to get right:
- Fit all external doors, windows and rooflights, and make sure they close properly.
- Seal around pipes and cables where they pass through walls, floors and ceilings, including behind boilers, baths and kitchen units.
- Seal around soil pipes, loft hatches and downlights.
- Check the junctions between walls, floors and ceilings, and around window and door frames.
- Finish the plasterboard, skirting and sealant before the test date.
- Make sure the tester has power and clear access to an external doorway for the fan.
Who can carry out the test?
Building Control can accept a certificate from a tester registered with an approved scheme, such as the Air Tightness Testing and Measurement Association. The tester must be trained and registered for that type of building. A test result is no use to you if Building Control will not accept it, so check before you book.
When should I book?
Near the end of the build, when the outer shell of the home is complete and sealed. Book with your handover date in mind, and leave time for a retest and the as-built SAP. The final EPC comes after those.
Frequently asked questions
How much does an air test cost?
Air tightness testing is From £95 + VAT (per plot). Guide price. Get a free quote for your project.
Does every new house need an air test?
Yes. Approved Document L says an air pressure test should be carried out on every new home, so plots are not sampled.
Does an extension need an air test?
Not usually. A test can help where a SAP calculation has assumed a better figure than the default.
What happens if my home fails?
The leaks need to be found and sealed, then the home is tested again until it meets the target. Sometimes the SAP can be rerun with the measured figure if the result is under the limit of 8, so ask us first.
Can I book Ventilation Testing on the same visit?
Yes. Ventilation testing is From £45 + VAT (per plot, on the same visit as other testing). Guide price. Get a free quote for your project.
Is the air test the same as a SAP calculation?
No. The SAP is a calculation of the home’s energy performance. The air test measures how much air actually leaks out, and that result goes into the as-built SAP.
Get a Free Quote for Your Project
Send us the site address, number of plots, your SAP target and the date you want the test.
Last reviewed: November 2026. Checked against Approved Document L Volume 1 (2021 and 2026 editions). General guidance for England only. Get project-specific advice before relying on it.