Construction & design PI

M&E design and the Building Safety Act: the professional indemnity angle

Category: Construction and design professional indemnity · Reviewed by the Apex broking team · Last reviewed 2026-08-22

In short: Mechanical and electrical design sits squarely inside the Building Safety Act regime, even though the duty-holder conversation is usually conducted in the language of architects, structural engineers and principal designers. Service penetrations through compartment lines, smoke control, detection and alarm interfaces and firefighting services all bear on the safety case for a building. For an M&E consultancy the insurance consequence is not a different policy — it is a much longer liability tail, a harder underwriting conversation, and a sharper need to define where your scope stops and the next discipline’s begins.

Why M&E design is inside the regime, not adjacent to it

The Building Safety Act 2022 and the regulatory architecture built on it are usually explained through the roles it names. Our guides on the Building Safety Act and professional indemnity insurance and on principal designer insurance set that framework out, and there is no value in restating it here.

What is worth saying is the thing M&E consultancies most often tell us they were not expecting: that a discipline which spends most of its time on plant selection, load calculations, distribution routes and commissioning turns out to be a fire-safety discipline as well. The building safety case for a higher-risk building is not confined to the structural frame and the facade. It reaches into how services cross fire compartment lines, how smoke is controlled and extracted, how detection is zoned, how the alarm system talks to lifts and dampers, and how the firefighting shaft is powered and pressurised.

Where M&E design actually touches building safety

The practical intersections are narrow, technical and well understood by the people who do the work. They include:

Service penetrations and compartmentation. Every duct, pipe, cable tray and containment run that crosses a compartment wall or floor is a designed breach of a fire barrier, and the specification of the firestopping and the coordination of who installs and inspects it is a design and interface question before it is a workmanship question.

Smoke control and ventilation. Smoke shafts, mechanical extract, natural ventilation openings, pressurisation of stairs and lobbies — the design intent, the modelling assumptions behind it and the interaction with the evacuation strategy are all M&E territory.

Detection, alarm and cause-and-effect. Zoning, the cause-and-effect matrix, interfaces with dampers, lifts, door releases, sounders and the fire alarm panel, and the commissioning evidence that proves it all behaves as designed.

Firefighting and life-safety services. Firefighting shafts, rising mains, evacuation and firefighting lift supplies, secondary power, emergency lighting and the resilience assumptions underneath them.

Suppression. Where a sprinkler or suppression system forms part of the fire strategy, its hydraulic design, water supply assumptions and coverage all become safety-critical rather than merely functional.

None of this is new engineering. What is new is that the regime treats these decisions as recorded, auditable and traceable through the life of the building, which changes how a claim looks when it arrives years later.

The limitation tail is the real underwriting problem

Section 135 of the Building Safety Act 2022 inserted a new section 4B into the Limitation Act 1980. The effect is a 15-year limitation period for claims under the Defective Premises Act 1972 and section 38 of the Building Act 1984 accruing after commencement, and a 30-year period for rights of action that had already accrued before the section came into force on 28 June 2022. Our page on Defective Premises Act limitation and PI cover deals with the mechanics.

For an M&E consultancy the point is blunt. A design decision taken on a residential scheme two decades ago can still be actionable, and the policy that has to answer for it is the one in force when the claim is made, not the one in force when the drawing was issued. That is what makes continuity of cover, an unbroken retroactive date and a properly funded run-off position matter far more than the price of any single year.

What this does to a claims-made programme

Professional indemnity is written on a claims-made basis, so a lengthening liability tail has three consequences that are worth planning for.

First, the retroactive date. If cover has ever lapsed, or if a change of insurer brought a later retroactive date with it, there is a window of historic design work with no policy behind it. That window does not close on its own, and under the extended limitation regime it stays exposed for a very long time.

Second, run-off. A practice that closes, merges or is bought still needs the claims tail funded. The conventional six-year run-off assumption was built around ordinary contractual limitation, and it does not sit comfortably against a 15-year or 30-year window on residential work.

Third, notification discipline. Circumstances that might give rise to a claim need to reach insurers in the policy year in which the practice becomes aware of them, and building-safety matters have a habit of surfacing as remediation surveys, gateway queries or building control correspondence rather than as letters of claim.

Interfaces: the scope question underwriters keep asking

Most M&E design disputes we see are interface disputes. Somebody assumed the fire engineer owned the smoke strategy; somebody else assumed the M&E consultant did. Somebody assumed the specialist contractor’s design portion covered the firestopping detail; the appointment said otherwise, or said nothing.

Underwriters read appointments and collateral warranties for exactly this. The questions that come back are consistent: what is the defined scope of service, is there a fitness-for-purpose obligation lurking in a schedule, who carries the design responsibility for contractor-designed portions, and are the warranties given no wider than the underlying appointment. Our notes on collateral warranties and your PI programme and on design liability on fit-out work cover the drafting side. The discipline-specific exposure profile is set out in how the engineering discipline shapes PI exposure. Design-and-build contractors approaching renewal can also read about using a specialist broker for design-and-build PI.

Fire safety and cladding exclusions

Since the market hardened, most PI policies written for construction professionals carry some form of fire safety, cladding or combustibility restriction. The wording varies enormously — from a narrow cladding-specific exclusion to a broad fire-safety carve-out that can reach smoke control and compartmentation work. For an M&E consultancy that does life-safety systems, the width of that clause is one of the two or three things that actually determine whether the policy is fit for the work. We set out the landscape in fire safety and cladding exclusions in PI insurance, and the wider placement picture for in-scope buildings in higher-risk buildings insurance.

How Apex approaches M&E design PI

We start with the work, not the proposal form. What proportion of fee income is residential, what proportion sits on buildings likely to be in scope of the higher-risk regime, what the practice designs itself versus reviews or coordinates, and where the appointments put the interface boundaries. From that we work back to the scope of the policy: retroactive date, the width of any fire safety restriction, how contractor-designed portions are treated, and whether the run-off position is realistic against the limitation regime the practice is actually exposed to. Presented that way, most M&E consultancies place perfectly well. Presented as a line on a schedule, the same practice can find the restrictions doing more work than the cover.

Frequently asked questions

Does the Building Safety Act apply to mechanical and electrical designers?

The Act and the regime built on it are organised around roles and around buildings rather than around professional titles. An M&E consultancy carrying out design work on a building within scope is doing safety-relevant design, and its decisions on compartment penetrations, smoke control, detection and firefighting services form part of the building's safety case. The practical answer is that M&E design sits inside the regime rather than alongside it.

How long can an M&E design claim be brought after the work?

Section 135 of the Building Safety Act 2022 inserted section 4B into the Limitation Act 1980, giving a 15-year period for claims under the Defective Premises Act 1972 and section 38 of the Building Act 1984 accruing after commencement, and 30 years for rights of action that had already accrued before 28 June 2022. Ordinary contract and tort limitation still applies to claims outside those routes.

Will a fire safety exclusion stop our PI policy responding to smoke control work?

It depends entirely on the wording. Some exclusions are confined to external wall systems and cladding; others are drafted broadly enough to catch fire strategy, compartmentation and life-safety systems generally. The clause needs to be read against the actual work the practice does before renewal, not after a notification.

What should we do about run-off if the practice closes?

Fund it deliberately and for a realistic period. Professional indemnity responds to claims made during the policy period, so once cover stops there is nothing to notify into. Given the extended limitation windows on residential building work, the traditional six-year assumption should be tested rather than adopted by default.