Professional indemnity insurance for draughtspeople and trades doing design work

Reviewed by Apex Insurance Brokers · Last reviewed 2026-08-05

Plenty of tradespeople take on design work without ever calling it design. You size a beam, set out a drainage run, specify a boiler and pipework layout, or draw up a steel frame in CAD. The moment you decide how something should be built rather than simply building to someone else's drawing, you have taken on professional responsibility — and a different kind of risk.

This guide explains where that liability comes from, why your existing insurance almost certainly does not cover it, when a contract or regulator effectively requires PI, and how Apex arranges the right cover for draughtspeople and design-and-build trades.

Where design liability comes from

Public liability (PL) insurance responds to injury or physical damage — a member of the public trips over your materials, or you flood the flat below. It is written to exclude the financial consequences of your professional advice or design. Professional indemnity is the policy built for exactly that gap: claims that you were negligent in a professional capacity and the client lost money as a result.

Design liability is easy to acquire without noticing. Common examples across the trades and drawing office include:

• Draughtspeople and CAD technicians producing setting-out drawings, fabrication drawings or construction details that others rely on and build to.
• Steel fabricators and metalworkers designing connections, brackets or a frame rather than fabricating to an engineer's drawing.
• Electricians designing a distribution board layout, fire alarm or emergency lighting scheme.
• Heating and plumbing engineers specifying heat loss calculations, boiler sizing or an underfloor heating layout.
• Kitchen, bathroom and shopfitters preparing design plans and specifications for a client to sign off.
• Groundworkers and drainage contractors deciding falls, levels and pipe runs.
• Builders offering “design and build” where you take responsibility for the design element as well as construction.

In each case the claim is not “something broke” — it is “the design was wrong, so the client had to tear it out, redo it, or absorb a loss.” That is a professional negligence claim, and it lands outside PL.

The gap most people don't realise they have

Say a fabricator designs a mezzanine support and the connection detail is under-specified. Nobody is hurt, but the structure has to be propped, redesigned and partly replaced. The main contractor pursues the fabricator for the cost of the remedial works and the delay to the programme. There is no injury and no third-party property damage in the sense PL contemplates — the loss flows from a defective design. Without PI, that claim, and the legal costs of defending it, sit with you personally.

This is why offering design work quietly changes your risk profile. Many trades assume their combined liability policy “covers everything.” It rarely covers pure financial loss caused by negligent design, and design and professional services exclusions are standard in PL wordings. If in doubt, read the exclusions on your current schedule — or ask us to.

Not sure whether your work counts as design? Tell us what you do and we'll check →

Is PI insurance legally required?

For most trades, PI is not a statutory requirement in the way that employers' liability is under the Employers' Liability (Compulsory Insurance) Act 1969. But two things commonly make it effectively compulsory in practice.

Contracts. If you work under a JCT contract with a Contractor's Design Portion, or a design-and-build form, the contract will usually specify a level of PI you must hold and maintain — often for a set number of years after completion. Main contractors, principal contractors and developers routinely make PI a pre-condition of being appointed. No policy, no place on the job.

Regulation. Under the Construction (Design and Management) Regulations 2015 (CDM 2015), anyone who prepares or modifies a design — including tradespeople and draughtspeople who take design decisions — is a “designer” with legal duties, regardless of job title. The Building Safety Act 2022 has further raised expectations on the competence of those carrying out design work, particularly on higher-risk buildings. Neither statute mandates PI directly, but both reinforce that design work carries accountability, and clients increasingly ask designers to evidence appropriate cover.

So the honest answer is: rarely required by law, frequently required by contract, and prudent whenever you take on design responsibility.

How much cover, and how the limit works

PI limits are typically offered as illustrative options such as £1m, £2m or £5m. The right figure depends on the value of the projects you design for, the contracts you sign, and what your clients require. A steel design error on a commercial frame can cost far more to put right than a domestic kitchen layout.

Two features of PI matter more than trades often expect:

Because of the claims-made structure, gaps in cover are dangerous. If you let PI lapse and a claim then arrives about last year's drawing, there may be no policy to respond. Continuity matters.

What PI typically covers — and what it doesn't

A professional indemnity policy for design-active trades and draughtspeople generally responds to:

• Claims of negligent design, drawings, specifications, calculations or professional advice.
• The cost of putting right or compensating for a design error that caused financial loss.
• Legal defence costs in investigating and defending such allegations.
• Related exposures often available by extension, such as breach of professional duty and, in some wordings, intellectual property or defamation cover.

It is not a warranty on your workmanship, and it does not replace public liability or employers' liability. Injury and physical damage stay with PL and EL; the quality of your design decisions is where PI does its work. Most trades doing design carry all three, so the injury claim, the damage claim and the design claim each have a home.

How Apex places cover for design trades

Apex Insurance Brokers is an FCA-authorised broker (FRN 724952) based in Bristol. We arrange PI for draughtspeople, CAD technicians and the growing number of trades taking on design-and-build responsibility. Our approach is practical:

• We map your real activities. The premium and the cover hinge on exactly what you design, for whom, and to what value — so we start there, not with a generic trade label.
• We match the limit to your contracts. If a JCT design portion or a client framework sets a required limit and run-off period, we make sure the policy meets it rather than falling short.
• We check the wording, not just the price. Claims basis, aggregate versus any-one-claim, and whether defence costs sit inside or outside the limit all change how a policy responds when it matters.
• We keep cover continuous. Because PI is claims-made, we help you avoid gaps and arrange run-off if you wind down or change what you do.

If you have moved from installing to designing — or you always designed and never insured it — that shift is worth a conversation before the next contract, not after the next claim.

Start your PI quote and tell us about your design work →

Common questions

I only occasionally tweak a design on site — do I really need PI?
Even occasional design decisions create design liability, and under CDM 2015 anyone who modifies a design counts as a designer. If a client could suffer a financial loss because a decision you made was wrong, PI is the policy that responds. How often you design affects the price, not whether the exposure exists.

Won't my public liability policy cover a design mistake?
Almost never. PL is written to exclude pure financial loss from professional advice or design, and design/professional services exclusions are standard. PL handles injury and physical damage; PI handles negligent design and advice. They are different policies for different risks.

What limit of indemnity should I choose?
It depends on the value of the projects you design for and what your contracts demand. Options are commonly offered at £1m, £2m or £5m. Where a JCT design portion or a client specifies a figure and a run-off period, your policy needs to meet it — we'll help you match the limit to your obligations.

Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority (FRN 724952). This guide is general information, not advice on a specific policy or a substitute for your policy wording.