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Contractors who design
Ductwork installers need professional indemnity insurance if they size ducts, produce coordination drawings, select fire dampers or lay out kitchen extract. Each is a design decision. Install-only work to a consultant’s design carries less professional risk, although site changes still count. Public liability is there for accidental injury and damage, not for a system that can’t deliver its airflow or a duct that undermines the fire strategy where it crosses a compartment wall.
Part of: Professional indemnity for design and build contractors
In short
Ductwork contractors take on design liability more often than they think: sizing ducts, drawing routes, choosing damper types and planning kitchen extract so it can be cleaned. In England, Approved Document B sets out four ways to keep fire resistance where ducts pass through fire-separating elements, and advises against fire dampers on kitchen extract because grease affects them. Since 1 October 2023, anyone doing design work must be competent and take reasonable steps so the design, if built, would comply with the Building Regulations. Many PI policies restrict fire safety work, so check that damper and fire-resisting ductwork design is covered.
Last reviewed 5 October 2026 by the Apex professional indemnity team.
Public liability (PL) pays for accidents. A length of duct that falls from a scissor lift onto a finished fit-out, or hot works that set insulation alight, are PL claims. The claims that hurt ductwork contractors tend to look different: a system that won’t move the air it was designed for, a fire damper in the wrong place, or kitchen extract that can’t be cleaned. Nobody had an accident. A design or specification decision was wrong.
PL policies generally exclude that kind of failure to perform, and they don’t respond to financial loss on its own. Professional indemnity (PI) is the policy for allegations that your design, advice or specification was negligent.
Ductwork contractors do more design than their job titles suggest:
These scenarios are illustrative rather than real claims. Each shows how an allegation against a ductwork contractor typically takes shape.
Some of these are design errors, some are specification errors, and one could be argued as workmanship. How a claim is framed often decides which policy responds, which is why the description of your business on the PI policy matters.
When a ductwork dispute reaches experts, they compare what you did with these references. Approved Document B is the guidance for England.
| Guidance or rule | What it says | Why it matters to you |
|---|---|---|
| Approved Document B, volume 2, para 10.12 | Where air handling ducts pass through fire-separating elements, fire performance must be kept using one or more of four methods: thermally activated fire dampers, fire-resisting enclosures, fire-resisting ductwork, or fire and smoke dampers triggered by smoke detectors. | Choosing the method is a design decision that has to fit the building’s fire strategy. |
| Approved Document B, volume 2, paras 10.14 and 10.15 | Neither type of damper should be used on extract ductwork serving kitchens, because grease build-up can affect them. Thermal dampers should not be used on extract ductwork through protected escape routes, as smoke can pass them without triggering them. | Two common design mistakes, and both are easy for building control to spot. |
| Approved Document B, volume 2, paras 10.17 to 10.19 | Dampers should sit within the thickness of the fire-separating element, be securely fixed, have access for inspection, testing and maintenance, conform to BS EN 15650 and be classified to at least 60 minutes’ integrity or the rating of the element, whichever is higher. | Installation details, not just product choice, decide whether a damper complies. |
| Building Regulations 2010, Part 2A (England, from 1 October 2023) | Anyone carrying out design or building work must have the competence to do it so that it complies. A designer must take all reasonable steps to ensure the design, if built, would comply with all relevant requirements. | Your design duty is now written into the regulations, not just your subcontract. |
| Building Regulations 2010, regulation 38 | Fire safety information must be given to the responsible person by completion or occupation. Approved Document B says records for complex buildings should cover fire dampers, fire and smoke dampers and smoke control dampers. | Damper schedules and locations are part of the handover, and gaps get noticed. |
| BESA DW/144 | The industry specification for sheet metal ductwork in low, medium and high-pressure systems, covering leakage classifications, sealing and access panel positions. | The benchmark for construction quality and leakage performance. |
| BESA DW145 and TR19 Grease | BESA’s good practice guide to installing and maintaining fire dampers, and its specification for managing grease in kitchen extract systems. | Experts will read your damper installation and kitchen extract design against them. |
Fire-related ductwork is where design, workmanship and insurance collide. Get the dampers wrong and compartmentation fails; get the kitchen extract wrong and grease turns the duct into a route for fire. These are exactly the claims many PI wordings now restrict. Fire safety exclusions come in different shapes: some remove anything touching compartmentation, fire stopping or fire safety systems, some apply only to external walls, and some give cover back for a lower limit shared across the policy year.
Before you rely on a policy, check:
On the technical side, a few habits keep your work defensible:
BESA notes that many insurance policies now require kitchen extract systems to be cleaned to TR19 standards, so a design that can’t be cleaned can cost the building owner more than the duct itself. For how these exclusions are worded, see fire safety and cladding exclusions in PI.
| Usually covered by PI | Often excluded or limited | Needs a different policy |
|---|---|---|
| Negligent duct sizing, routing and system design | Fire safety work, including dampers and compartmentation, unless the policy expressly covers it | Accidental damage to the building or other trades’ work during installation (public liability) |
| Errors in coordination and fabrication drawings | The cost of remaking or refitting your own defective ductwork | Injury to your own operatives (employers’ liability) |
| Wrong selection or specification of dampers, fans and grilles | Fitness for purpose obligations and performance guarantees in subcontracts | Damage to ductwork and materials before handover (contract works) |
| Negligent advice to a client or M&E contractor, including value engineering proposals | Liquidated damages for late completion | Hired-in access equipment (hired plant cover) |
| Defence costs and experts’ fees | Claims you knew about before the policy started | Injury or damage caused by products you manufacture (products liability) |
Read how the policy describes your business. “Ductwork installation” on its own may not extend to design, coordination drawings or damper selection. Any cover depends on the insurer accepting the risk and on the wording it issues.
Most ductwork contractors work as subcontractors, so the limit comes from the M&E or main contractor. A subcontract with a contractor’s design portion usually names a PI figure and a number of years after practical completion for which cover must be maintained, and it may require collateral warranties to the employer, funders or tenants. Check two things before signing: whether the limit has to apply to each and every claim, and whether your policy’s fire safety sub-limit falls below the contract figure.
PI is claims-made, which matters because ductwork problems surface late: at commissioning, at the first damper drop test, or after a fire, often long after you have left site. The policy you hold when the claim arrives is the one that responds, so cover has to continue after the work is finished, and run-off cover is needed if you stop trading.
Related reading: collateral warranties and PI and what to do when a contract requires a higher PI limit.
A complete proposal gets better terms than a bare one, and a broker can only present what you tell us. Have these ready:
Speak to a broker
PI for ductwork installers, placed by a named broker
Start the online proposal and save it as you go, or leave your number and a named broker will call you back, usually the same working day.
Apex Insurance Brokers is an independent insurance broker based in Bristol, established in 2009 and authorised and regulated by the Financial Conduct Authority. We are not tied to one insurer: we work with over 30 markets, including Lloyd’s syndicates through wholesale brokers, and every client has a named broker who handles the placement, mid-term changes, certificates for clients and the renewal.
They do whenever they size ducts, produce coordination or fabrication drawings, select fire dampers or design kitchen extract. Public liability is for accidental injury and damage, and it usually won’t respond when a system simply underperforms. PI answers allegations of negligent design and specification, subject to the policy terms.
No law requires ductwork contractors to hold PI. In England the Building Regulations require anyone doing design work to be competent and to take reasonable steps so the design complies, but that is a duty, not an insurance requirement. In practice M&E and main contractors set PI requirements in subcontracts.
Only if the policy says so. Many PI wordings exclude or sub-limit fire safety work, and fire dampers, fire-resisting ductwork and smoke control can fall within those exclusions. Tell the insurer about this work and check the wording before you rely on it.
Your design exposure is lower, but rarely zero. Coordination and fabrication drawings, re-routing on site, value engineering proposals and damper selection are all design decisions. If you make any of them, you need a PI policy that describes them.
It can, subject to the policy terms. Claims usually allege a layout that couldn’t be cleaned, or protection at compartment walls that didn’t follow Approved Document B, which advises against dampers on kitchen extract. Tell your insurer you do this work and check any fire safety exclusion.
If the shortfall comes from your design, such as undersized ducts, the client may claim the cost of fixing it and the delay. PI can respond to that claim, subject to the policy terms. Reworking your own installation where the fault is purely workmanship is usually excluded.
Apex arranges professional indemnity insurance for ductwork installers across the UK. Tell us about your work and we’ll find cover that fits. Or call 0117 325 0027.
Start your PI proposal Call 0117 325 0027Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority. Registered in England and Wales, company number 07014570. This page is general information, not advice on your individual circumstances. Cover is always subject to the insurer’s acceptance and the policy terms, and this page does not guarantee that cover will be available or on what terms.
