Building Regulations Part L Compliance Made Simple
Meeting Part L Building Regulations in domestic settings should not delay your programme.
At Stroma, our structured approach to air permeability testing ensures your project is prepared, tested and reported efficiently to help you achieve compliance without unnecessary delays or site disruption.
We provide reliable home air tightness testing that supports SAP calculations, Building Control sign-off and smooth handover for both single dwellings and multi-unit developments.
Expert Air Permeability Testing
Air permeability testing is a mandatory requirement under Building Regulations Part L for all new homes and large extensions. The test measures uncontrolled air leakage through the building envelope and forms a critical part of SAP compliance.
At Stroma Built Environment, our qualified air permeability testing team make the process straightforward and stress-free. We deliver efficient testing, designed to minimise disruption while helping you achieve compliance with accurate and defensible results to meet your building handover deadlines.
Why Choose Stroma for Domestic Air Testing?
With over 20 years' of industry experience and a team of highly skilled ATTMA-certified engineers, we're one of the UK's largest and most trusted air testing providers of home air leakage testing and home air tightness testing.
At Stroma, we understand the commercial pressures faced by developers and contractors and provide practical guidance to help achieve first-time compliance under Part L in domestic settings.
We’re trusted by national and regional housebuilders to support phased residential developments across the UK, with structured air permeability testing in alignment with programme deadlines.
What sets us apart:
- Expert diagnostics without unnecessary remediation – Our experienced air permeability tester engineers quickly identify leakage pathways efficiently using methods aligned with ATTMA TSL1 to help prevent costly repeat visits.
- Clear preparation guidance – Practical advice on sealing strategies and envelope continuity to support compliant air permeability testing under Building Regulations Part L 2021.
- UKAS accredited testing (Laboratory No. 2731) – All testing is delivered under our accredited laboratory status to ensure results are suitable for SAP and Building Control submissions.
- Transparent testing process –Testing is carried out in accordance with ATTMA TSL1 and CIBSE TM23 guidance, with clear explanations provided on site.
- Rapid turnaround – Most home air tightness testing is completed in 1-2 hours with detailed reports delivered within 48 hours
Our Domestic Air Testing Service
We provide comprehensive air permeability testing in full compliance with ATTMA TSL1 and CIBSE TM23 standards, ensuring full alignment with Part L domestic requirements.
Our service includes:
- Pre-test consultation – Guidance on temporary and permanent sealing strategies to maximise your chances of passing
- Calibrated blower door systems – Professional-grade equipment operated by a certified air permeability tester for accurate, reliable results
- On-site testing – Typically 1-2 hours per dwelling
- Smoke diagnostics – If home air leakage testing fails, we use targeted smoke testing to identify air leakage paths quickly and effectively
- Comprehensive reporting – Detailed test results and feedback within 48 hours, suitable for SAP calculations and Building Control submission
- Remedial sealing support – If remediation is required, our specialist sealing team can help get your building back on track
- National coverage – Our experienced air permeability tester engineers operate across the UK
- Volume and phased testing support – Structured home air tightness testing for multi-plot developments and phased handovers
- SAP coordination – Close liaison with SAP assessors to ensure Part L domestic alignment and smooth compliance reporting
What to Expect on Test Day
Our experienced air permeability tester will arrive on site with calibrated blower door equipment and conduct a thorough air permeability test in accordance with ATTMA TSL1/CIBSE TM23 methodology. The test measures the volume of air leakage at 50Pa, providing an accurate air permeability rate used within SAP calculations.
We'll explain the process as we go, answer any questions, and provide immediate feedback on results.
Common concerns we address:
- How long will the engineer be on site?
- What temporary sealing do I need to complete beforehand?
- How will I know if we've passed or failed?
- What happens if we fail the test?
Our experienced engineers provide clear, practical answers to all these questions and more.
Building Regulations Part L Domestic Compliance
Under Building Regulations Part L for domestic dwellings, air permeability testing is mandatory for all new builds and extensions over 25% of the existing building. The objective is to limit uncontrolled air leakage, improving energy efficiency and supporting SAP compliance.
Building Regulations Part L 2021 came into effect on 15th June 2022, significantly tightening air permeability requirements. The maximum permitted air permeability was reduced from 10 m³/(h·m²) to 8 m³/(h·m²) at 50Pa—a 20% improvement requirement.
What this means for your project: The notional building specification (the benchmark against which your building is compared) uses an air permeability of 5 m³/(h·m²). This means that while 8 m³/(h·m²) is the absolute maximum, achieving closer to 5 m³/(h·m²) will make it much easier to pass your SAP calculations and meet overall energy performance requirements.
With reduced margins for error, professional home air leakage testing delivered by an experienced air permeability tester is crucial to achieve first-time compliance.
With over 20+ years of industry experience and practical expert guidance on sealing strategies, we help developers achieve compliant results within today’s more demanding regulatory environment.
Stricter Regulations Since June 2022
The 2022 update to Part L domestic introduced tighter air leakage targets:
- Old target (pre-June 2022): 10 m³/(h·m²) at 50Pa
- New target (from June 2022): 8 m³/(h·m²) at 50Pa
- Notional building baseline: 5 m³/(h·m²) at 50Pa (the realistic target for SAP compliance)
What this means for you: This 20% reduction in acceptable air leakage (from 10 to 8) means buildings must be significantly more airtight than before. While 8 m³/(h·m²) is the absolute maximum, the notional benchmark of 5 m³/(h·m²) is often the realistic target to support SAP calculations and achieve compliant air permeability testing results.
Looking ahead, the introduction of the Future Homes Standard signals continued tightening of performance expectations, with 5 m³/(h·m²) becoming the anticipated norm. Now is the time to develop robust home air tightness testing strategies and work with experienced testing partners to protect programme certainty and future compliance.
Partner with Stroma for Stress-Free Air Testing and Building Regulations Compliance
At Stroma, our structured approach to air permeability testing helps improve first-time pass rates, reduces repeat visits and supports efficiency under Part L domestic compliance across single and multi-unit developments UK-wide.