Air Tightness Testing

ATTMA-accredited air pressure testing from just £95 per dwelling. Our engineers provide same-day certificates, clear site preparation checklists, and on-site diagnostics if your building does not meet its target. UK Building Compliance delivers Part L compliant air tightness testing for new builds, commercial buildings, and retrofit projects nationwide — helping you pass first time and avoid costly delays.

What Is Air Pressure Testing?

An air pressure test (also called an air tightness test, air permeability test, or blower door test) measures how much air escapes through gaps and cracks in your building's envelope. The test is carried out by temporarily sealing the building and using a calibrated fan to pressurise or depressurise the space, then measuring the airflow required to maintain that pressure.

The result is your building's air permeability rating, expressed in m³/h/m² @ 50Pa — essentially how many cubic metres of air leak through each square metre of building envelope per hour at a test pressure of 50 Pascals. This measurement provides a clear, standardised indication of how well-sealed the building is.

Uncontrolled air leakage can account for up to 40% of a building's heat loss, significantly increasing energy bills and carbon emissions. A well-sealed building maintains comfortable temperatures with lower heating costs, which is why air pressure testing is a critical part of the building compliance process.

Why Do You Need Air Pressure Testing?

Under Part L of the Building Regulations (Part L1A for dwellings, Part L2A for non-dwellings), all new builds in England and Wales must undergo air tightness testing. Similar requirements exist in Scotland (Section 6) and Northern Ireland (Part F1). Since June 2022, every new-build plot requires its own individual test — sampling is no longer permitted.

The maximum allowable air permeability under Part L is 8 m³/h/m² @ 50Pa. However, your specific target is set by your SAP or SBEM calculations at the design stage. Most new-build dwellings target 5 m³/h/m² @ 50Pa or below to meet their energy performance requirements.

Without a passing air tightness test certificate, your building cannot achieve building control sign-off. This means completion certificates, handovers, and property sales can all be delayed — making it essential to prepare thoroughly and test at the right time.

Our Air Pressure Testing Process

UK Building Compliance makes air pressure testing straightforward and stress-free. Our ATTMA-accredited engineers follow a proven process designed to maximise your chances of a first-time pass.

1. Pre-test preparation — We send you a clear site readiness checklist before we attend, so you know exactly when your plot is ready for testing. This covers sealing temporary openings, ensuring all windows and doors are fitted, and checking that service penetrations are properly sealed.
2. Equipment setup — Our engineer installs the calibrated blower door fan in an external doorway and temporarily seals any intentional ventilation openings such as trickle vents and extract fans.
3. Pressurisation and depressurisation — The fan pressurises the building to 50 Pascals while measuring the airflow rate. The test is then repeated in depressurisation mode to produce an averaged result.
4. Result calculation — The average airflow is divided by the total building envelope area to produce the air permeability result in m³/h/m² @ 50Pa.
5. Same-day certification — If your building passes, we issue the air tightness test certificate on the same working day, keeping building control and handovers on schedule.
6. Diagnostics if needed — If your building does not meet its target, we identify the main leakage paths using smoke testing and pressure diagnostics, then explain exactly how to fix them before a re-test.

What's Included

• ATTMA-accredited air permeability test to Part L standards
• Pre-test site readiness checklist sent in advance
• Same-day test certificate when you pass
• On-site smoke testing and diagnostics if you fail
• Practical guidance for your site team on common leakage points
• Testing for both dwellings (from £95 + VAT) and commercial buildings (from £150 + VAT)
• First-time pass support guarantee — follow our checklist and still fail, and we waive the re-test call-out fee

Air Pressure Testing for Every Project Type

• New-build dwellings — Part L1A compliant testing for houses, flats, and apartments against your SAP design target.
• Commercial buildings — Part L2A compliant testing for offices, retail units, schools, healthcare facilities, warehouses, and industrial buildings, coordinated around your programme.
• PAS 2035 retrofit projects — Pre- and post-retrofit testing to demonstrate the airtightness improvement achieved by energy efficiency measures.
• Passivhaus projects — Testing to the significantly tighter Passivhaus standard of 0.6 air changes per hour @ 50Pa.

Common Reasons Buildings Fail Their Air Test

Understanding the most common failure points helps you prepare effectively. Typical air leakage issues include:

• Gaps around service penetrations (pipes, cables, ducts passing through the building envelope)
• Poorly sealed window and door frames
• Gaps at junctions between walls, floors, and ceilings
• Unsealed loft hatches and access panels
• Gaps around mechanical ventilation ductwork where it passes through the envelope
• Incomplete sealing at the wall-to-floor junction

Our pre-test checklist and on-site guidance help you address these issues before the test, significantly improving your chances of a first-time pass.

Why Choose UK Building Compliance?

UK Building Compliance has carried out thousands of air pressure tests for housebuilders, developers, and commercial clients across the UK. Our engineers are fully ATTMA-accredited, and we hold additional accreditations with Stroma, ABBE, BPEC, Elmhurst, and UKAS.

We offer a complete building compliance service, meaning your air tightness testing can be combined with sound insulation testing, ventilation testing, and SAP calculations in a single coordinated visit — saving you time and reducing disruption on site.

Based in Hinckley, Leicestershire, we provide nationwide coverage with competitive pricing and rapid availability. Call us on 01455 242297 or request a quote online.