How to Prepare a Commercial Building for an Air Tightness Test

Practical checklist on how to prepare a commercial building for an air tightness test for UK businesses

Preparing a commercial building for an air tightness test is essential if you want to achieve a first‑time pass and avoid costly delays. Whether you’re working on a warehouse, office, retail unit, school, or industrial facility, proper preparation ensures your building meets the requirements of Approved Document L (Part L) and performs efficiently once occupied.

This guide provides a practical, step‑by‑step checklist to help UK businesses prepare their commercial buildings for a successful air tightness test — with links to our in‑depth blogs and service pages for further guidance.

Why Preparation Matters for a Commercial Air Tightness Test

Air tightness testing measures how much air escapes through gaps, cracks, and penetrations in the building envelope. Poor preparation leads to:

Failed tests
Retesting costs
Delays in Building Control sign‑off
Increased energy consumption
Poor EPC ratings

To understand how leakage paths form, see our knowledge article:
👉 Air Leakage Paths Found During Thermal Imaging Surveys

Step‑by‑Step Checklist for Preparing a Commercial Building for air testing

Below is a practical checklist designed specifically for commercial buildings.

1. Ensure the Building Envelope Is Complete

Before testing, the building must be as close to finished as possible. This includes:

All external doors and windows installed
Cladding and façade systems complete
Roof and wall junctions sealed
Service penetrations closed and sealed

For examples of common leakage points, see:
👉 Common Air Leakage Paths Identified During Air Tightness Testing

2. Seal All Service Penetrations

Commercial buildings often contain hundreds of penetrations for:

Electrical cables
HVAC ductwork
Plumbing
Fire stopping
Data cabling

Every penetration must be sealed with appropriate materials. Unsealed penetrations are one of the most common causes of test failures.

Learn more about identifying leakage paths here:
👉 Air Leakage Paths Found During Thermal Imaging Surveys

3. Close All Ventilation Systems and Dampers

Before the test:

Turn off mechanical ventilation
Close all dampers
Seal open ductwork
Ensure trickle vents are closed

If ventilation systems remain open, the building will fail.

4. Check External Doors and Shutters

Commercial buildings often have:

Roller shutter doors
Fire exits
Loading bay doors

These are major leakage points. Ensure:

Door seals are installed
Thresholds are sealed
Shutters close tightly

For more guidance, see:
👉 Smoke Leakage Surveys to Pass Air Tightness Testing

5. Inspect Internal Areas for Air Leakage Paths

Internal leakage can occur around:

Lift shafts
Risers
Stairwells
Suspended ceilings
Plant rooms

These areas often connect directly to the outside envelope.

If you suspect hidden leakage, smoke testing can help:
👉 Smoke Testing Service to find air leakage paths

6. Ensure All Wet Trades Are Complete

Wet trades such as plastering, screeding, and sealing must be finished and dry. Wet materials can affect pressure readings and cause inaccurate results.

7. Prepare the Building for Pressurisation

On the day of the test:

Turn off heating and cooling systems
Close all internal doors
Ensure all personnel are aware of the test
Provide clear access to the main entrance for blower door setup

For a full breakdown of the testing process, see:
👉 Our Air Tightness Testing Procedure

What Happens If the Building Fails the Part L Air Tightness Test?

If your commercial building fails the air tightness test:

It cannot be signed off by Building Control
Remedial sealing work is required
Retesting may be necessary
Project delays and additional costs may occur

APT Sound Testing can provide on‑site diagnostics, including smoke tracing and thermal imaging, to quickly locate and fix leakage paths.

Explore our diagnostic services:
👉 Thermal Imaging Surveys

👉 Smoke Testing for AOV Smoke Shafts

Why Proper Preparation Saves Time and Money

A well‑prepared building:

Passes first time
Avoids costly delays
Reduces energy bills
Improves EPC ratings
Ensures Part L compliance
Enhances long‑term building performance

How APT Sound Testing Helps Commercial Clients

APT Sound Testing provides:

UKAS‑accredited commercial air tightness testing
ATTMA Level 2 certified engineers
High‑capacity, UKAS‑calibrated blower door systems
Smoke leakage diagnostics
Thermal imaging surveys
Pre‑test inspections
Nationwide coverage

Explore our full service offering:
👉 Air Tightness Testing Services

📞 Contact Us Now

APT Sound Testing is a UKAS‑accredited testing laboratory and an ATTMA Level 2 certified air‑tightness testing provider, giving you complete confidence that your commercial building will be tested to the highest industry standards.

We use the latest modular, UKAS‑calibrated blower door systems, capable of testing everything from small commercial units to large warehouses and complex multi‑storey buildings. Our advanced diagnostic tools — including smoke tracing and thermal imaging — ensure fast, accurate identification of air leakage paths so your project passes first time.

👉 Contact us today at info@aptsoundtesting.co.uk or call Darren on 077775623464 to book your commercial air tightness test and ensure full compliance with UK Building Regulations.