ATSPACE helped an office fit-out achieve a first-time pass on its commercial air leakage (pressure) test by controlling the basics: readiness checks, airtightness close-out across interfaces, and a planned test sequence that avoided last-minute rework. The result was Part L‑aligned evidence at practical completion without programme disruption.

Project Snapshot

Service: Commercial Air Leakage Testing (Non-domestic pressure testing)
Client: Principal contractor (CAT A/CAT B fit-out) – anonymised
Building type: Office (refurb + fit-out)
Location: Meridian House, Kingsway Business Quarter, Birmingham (address anonymised)
Size: Approx. 4,600 m² over 5 floors
Programme stage: Pre-PC / commissioning window
Regulatory driver: Part L (non-domestic compliance evidence)
ATSPACE team: Accredited Airtightness Test Engineer + Compliance Coordinator

What Made This Job Risky

Office fit-outs fail airtightness tests for different reasons than new‑build housing. The building can appear “finished”, but airtightness performance breaks down at the interfaces.

This project had three classic fit‑out risk factors:

1) The airtightness line crossed multiple scopes

The airtightness layer wasn’t owned by a single trade. It ran through:

• base-build façade and risers
• fit-out partitions and ceilings
• M&E penetrations (fan coils, ductwork, sprinkler pipework, data routes)
• fire stopping in service zones
• door sets, thresholds and access panels

If these scopes don’t join up, leakage appears fast.

2) Late-stage changes were still happening

As with most offices approaching PC:

• last-minute data/containment additions
• ceiling tile lifts and reinstalls
• access panel changes
• “one more penetration” into risers or plant

These changes can undo airtightness work in a single day.

3) A failed test would have hit programme and cost hard

A failed test in commercial fit-out often triggers:

• delayed PC evidence
• re-access above ceilings and behind finishes
• disruption to commissioning
• out-of-hours remedials
• retest delays (and disputes)

The client didn’t want a test — they wanted certainty.

What Is a Commercial Air Leakage Test (Plain English)

A commercial air leakage test measures how much uncontrolled air escapes through the building envelope under pressure.

Why it matters:

• supports energy performance and Part L
• reduces heat loss and improves HVAC stability
• proves the building performs as intended at PC
• avoids “paper compliance” that doesn’t match reality

ATSPACE’s role is to make that outcome repeatable, not lucky.

The Brief to ATSPACE

The contractor asked ATSPACE to:

• carry out the commercial pressure test within a tight pre‑PC window
• reduce retest risk by identifying weak points before test day
• support close-out with practical, achievable guidance
• provide clear reporting suitable for compliance and handover

What ATSPACE Did (The Method That Makes First-Time Passes Normal)

Step 1: Airtightness readiness review (before test day)

We completed a targeted walkdown with the site manager and M&E lead, focusing on the leakage routes that most commonly fail office fit-outs.

Typical high‑risk items on this job:

• riser doors and access panels (seal continuity + latching)
• ceiling void penetrations (sprinklers, ductwork, containment, pipe drops)
• façade-to-slab and façade-to-ceiling junctions
• plant and comms room service entries
• perimeter glazing interfaces and thresholds
• roof upstands, hatches and smoke vents (if applicable)

These points cause most retests in commercial buildings.

Step 2: Close-out actions trades could actually deliver

We gave practical, trade-friendly guidance such as:

• ensuring access panels have continuous compressible seals
• confirming penetrations are sealed as part of fire stopping
• sealing door thresholds and frame-to-structure gaps behind trims
• controlling ceiling tile lifts post sign-off (to prevent broken seals)

The goal was simple: eliminate rework before it occurs.

Step 3: Test-day control (conditions, sequencing, evidence)

On test day, ATSPACE controlled:

• zoning and door positions
• temporary sealing arrangements (only where appropriate)
• internal pressure equalisation routes
• the test sequence to maintain stability and minimise disruption

Step 4: Reporting that doesn’t create admin pain

We delivered:

• clear test results and test conditions
• compliance-ready certification
• concise learning notes for future phases

The Real Problems We Faced (And How They Were Solved)

Problem A: Riser access panels looked complete—but weren’t airtight

A few riser panels had inconsistent compressible seals and uneven closure pressure.

Fix: confirm continuous seals and correct latching.
Why it matters: risers behave like vertical leakage chimneys.

Problem B: Ceiling void penetrations were still being modified

Containment routes and M&E details were still being adjusted late.

Fix: agree a penetrations “freeze point” and seal unavoidable late works immediately.
Why it matters: these late changes are a leading cause of failed first tests.

Problem C: Threshold detailing around plant/service doors

Multiple materials met at thresholds, creating gaps.

Fix: verify seal continuity before finishes locked the interface in.
Why it matters: small threshold leaks can have a large impact in commercial spaces.

Results

• Commercial air leakage test passed first time
• Part L‑aligned evidence achieved at practical completion
• No retest programme impact
• Reduced disruption to commissioning and defects
• Reporting ready for handover packs

What This Project Proves

On office fit-outs, airtightness success comes down to interface control.

Airtightness sits between:

• base build and fit-out
• fire stopping and M&E
• ceilings and risers
• door sets, frames and thresholds

When these interfaces are controlled early, first-time passes stop being luck.

Common Mistakes on Office Fit-Out Airtightness Testing

• booking tests before risers are properly closed out
• allowing ceiling tile lifts after “readiness” is declared
• relying on trims instead of sealing the air path
• inconsistent seals on access panels and service doors
• incomplete fire stopping around services

CTA

If your office fit-out is approaching PC and you need a first‑time commercial air leakage test pass, ATSPACE can support with:

• airtightness readiness walkdowns
• commercial pressure testing
• rapid troubleshooting if readings are inconsistent
• compliance-ready evidence for handover

FAQ

What is the difference between domestic and commercial airtightness testing?
Commercial testing has larger volumes, more complex service routes, and more interface risk. The principle is the same—control leakage pathways—but the failure points differ.

When should we book commercial pressure testing?
When envelope interfaces are complete and penetrations are controlled—ideally after a readiness review so the test slot isn’t a gamble.