You need professional liability, also called E&O, if you do more than build to someone else's plans, so if you design, spec, engineer, or design-build, because your general liability will not respond to a design mistake at all. GL is triggered by an accidental physical event; a flaw in your drawings or specifications is a professional error, which sits entirely outside GL. If you only install exactly what an engineer or architect specified, you probably do not need it.
Why general liability won't cover a design mistake
General liability responds to an "occurrence," an accidental physical event that causes bodily injury or property damage. A professional error is not an accident. Bad design, the wrong specification, a faulty calculation, or a negligent inspection are all failures of professional judgment, not physical accidents, so GL does not respond to them.
That is the gap professional liability fills. If you carry design or engineering responsibility on a job and rely only on GL, you are uninsured for the exact risk that responsibility creates.
Who actually needs E&O
You likely need E&O if you:
- Are a design-build contractor.
- Design, spec, or engineer any part of the work.
- Provide value engineering or shop drawings that change the design.
- Sign a contract that makes you responsible for a professional standard of care on the design, not just workmanship.
You likely do not need it if you are a pure installer building to a sealed set of plans somebody else stamped. The test is simple: does your contract make you responsible for whether the design is adequate, or only for whether your work matches the plans? Responsibility for the design is the trigger.
What E&O covers
A professional liability / E&O policy for contractors typically covers:
- Design errors and omissions in drawings, specifications, or calculations.
- Negligent supervision or inspection.
- Faulty-workmanship claims where the cause traces back to a professional error rather than a physical accident.
- On contractor-specific E&O forms, things like use of defective materials and recall of work.
Some contractor E&O endorsements also reach into the "your work" gap that GL excludes, which is worth asking about if redoing your own defective work is a real exposure for you.
It's claims-made: mind the retroactive date and tail
Professional liability is almost always claims-made, not occurrence. That has three consequences you have to manage:
- The policy must be active when the claim is filed, not just when the work was done.
- A retroactive date sets how far back covered acts reach. Work done before that date is not covered.
- You need tail coverage (an extended reporting period) when you switch carriers or close the business, or a claim that lands after the policy expires is uninsured, even for work you did while insured.
Never let a gap open between the incident and reporting, and never drop the policy the day you retire without buying tail. This is the same discipline that makes claims-made risky for general liability, which is why you insist on occurrence for GL but accept claims-made for E&O.
The design-build premium reality
Design-build carries both the physical construction risk and the professional design risk, so carriers price it higher than E&O for a pure design firm. Expect design-build E&O to cost meaningfully more than a plain design professional's policy, because you are holding two exposures at once.
For large or complex jobs, project-specific professional liability (PSPL) can cover the entire design team, including subconsultants, for that one project. And on limits: set your per-claim limit above the value of your largest project, because a single design failure can put the whole project value at risk.
Common questions
What's the difference between general liability and professional liability?
General liability covers physical accidents, bodily injury, and property damage; professional liability covers mistakes in your professional work, like a design error or bad specification. GL is triggered by an accidental event and will not respond to a flaw in your drawings or engineering. If you design, spec, or design-build, that design exposure sits entirely outside GL, so you need professional liability (E&O) to cover it. Pure installers building to someone else's stamped plans generally only need GL.
Do I need E&O if I only build to the architect's plans?
Usually no. If you are a pure installer building to a sealed set of plans that someone else designed and stamped, your general liability generally covers you and E&O is not required. E&O matters when you carry design responsibility yourself, through design-build, speccing, engineering, or value engineering that changes the design. The test is whether your contract makes you responsible for whether the design is adequate, not just whether your work matches the plans. If you only own the workmanship, GL is usually enough.
Is E&O insurance occurrence or claims-made?
Almost always claims-made. The policy must be active when the claim is filed, not just when you did the work, and a retroactive date limits how far back covered acts reach. That means if you switch carriers or close the business, you need tail coverage (an extended reporting period), or a claim filed after the policy ends is uninsured even for work you did while covered. This is the opposite of the occurrence form you insist on for general liability, so E&O needs active management of dates.
What is tail coverage and when do I need it?
Tail coverage, an extended reporting period, lets you report claims after a claims-made policy ends, for work you did while it was active. You need it whenever you switch professional liability carriers or close the business, because without it, a claim that arrives after the policy expires is uninsured, even though the work was done during the covered period. Design and defect claims often surface years later, so dropping a claims-made policy without buying tail can leave you exposed for old work.
The honest bit
- E&O premiums vary widely by scope, design exposure, and firm size, so it is a get-a-quote item, not a number you can look up.
- Because it is claims-made, the retroactive date and tail coverage are as important as the limit. Read them, and never let a coverage gap open.
- This is general guidance, not legal or insurance advice. If your contract imposes a professional standard of care, have it reviewed, and route state licensing rules for design work to Working in Your State.
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