A structural issue surfaces six months after project close. The owner’s legal team traces the cause to a design decision made during the integrated planning phase. Your general liability carrier receives the claim and issues a denial. Design errors are not a general liability exposure. They are a professional liability claim. You do not carry that coverage.
This is not an edge case. It is a gap that exists in the majority of small and mid-sized design-build firms operating today, and as design-build project delivery continues to grow, so does the exposure.
Why Design-Build Blurs Every Liability Line
In traditional project delivery, the liability separation is relatively clean. The architect or engineer carries professional liability — also called errors and omissions, or E&O — for design decisions. The general contractor carries general liability for construction execution. Claims fall into distinct buckets.
Design-build collapses that structure. When one entity holds both design and construction obligations under a single contract, the liability for problems at the intersection of design and construction lives entirely with the design-build contractor. The owner does not need to sort out whose error caused the problem. The design-build entity owns all of it.
According to the Design-Build Institute of America, design-build now accounts for more than 44% of US construction volume across commercial, institutional, and infrastructure sectors — a share that has grown steadily for over a decade. Engineering News-Record has reported that as design-build projects grow in size and complexity, more project owners are contractually shifting risk back to the design-build contractor, with insurance requirements as the primary mechanism.
General liability covers third-party bodily injury and property damage caused by your operations. It does not cover pure economic loss arising from a design error, an omission in drawings, or a specification that turns out to be wrong. Those claims fall under professional liability and without a professional liability policy, the design-build contractor is uninsured for them.

What Professional Liability Actually Covers
A professional liability policy covers claims arising from negligent acts, errors, or omissions in the performance of professional services. For design-build contractors, that means structural or mechanical errors in design documents, failure to meet code requirements identified during design, cost overruns caused by inaccurate specifications or scope documents, and third-party claims for economic loss tied to design decisions.
GL and professional liability do not overlap. They are designed to cover fundamentally different categories of loss. A project with a design flaw that causes water intrusion damage could generate both a GL claim for the property damage and a professional liability claim for the cost to redesign and correct the underlying error. Full protection requires both policies.
One additional detail matters here: professional liability policies are typically written on a claims-made basis, meaning the coverage in force when a claim is reported is what applies — not necessarily the coverage in place when the alleged error occurred. Maintaining continuous coverage and understanding the retroactive date on your policy is essential.
What Project Owners Are Requiring Right Now
Carrying professional liability is no longer just about internal risk management. More project owners, particularly on institutional, municipal, and private commercial work, are contractually requiring evidence of professional liability coverage before executing design-build agreements.
Sophisticated owners have become aware of the coverage gap and are shifting that risk back to the contractor through insurance requirements and indemnification language. If you are pursuing work where professional liability is a contract requirement and you do not carry it, you are either losing bids or misrepresenting your program.
A specialty programs review with an experienced broker can clarify what coverage limits are appropriate for your project types, whether your current commercial insurance program has any incidental professional liability extensions, and how to structure both policies so they work together without gaps or overlap.
Ready to make sure your design-build operation is fully covered? The team at Tooher-Ferraris has been helping contractors protect their businesses since 1932. Contact us today to schedule a no-obligation consultation.





