Errors and omissions insurance, called professional liability or E&O in the design context, is the coverage that addresses what general liability explicitly excludes for design-build contractors. Understanding how it works, when it responds, and how to size it appropriately is foundational to building an insurance program that actually covers the exposure profile design-build project delivery creates. Here are the four most important questions design-build contractors ask about E&O coverage, answered directly.
What Does E&O Insurance Actually Cover for a Design-Build Contractor?
E&O insurance covers claims arising from professional services — the design decisions, specifications, calculations, drawings, and professional advice that constitute the design component of a design-build project. When a claim alleges that a design error, specification failure, or professional judgment call caused damage or loss to a project owner or third party, E&O is the policy that responds.
The coverage grant in a design-build E&O policy is typically framed around “wrongful acts” in the performance of professional services. A wrongful act is a negligent act, error, or omission in the performance of professional services that results in a claim. The coverage does not require that the design-build firm intended to make an error. It requires that a claimant can establish that a professional services failure occurred and that the failure caused a loss.
In practical terms, E&O responds to claims such as: a waterproofing system failure attributed to a specification error in the waterproofing detail; a structural element that fails to perform as designed due to a calculation error; a mechanical system that does not meet performance specifications because of a design coordination error between disciplines; and a project that cannot be occupied because a code compliance error in the design requires expensive remediation. These are all professional services failures, and none of them are covered by a standard commercial general liability policy.
How Is E&O Different From General Liability — and Why Do Design-Build Firms Need Both?
The distinction between E&O and GL coverage is fundamental to understanding why design-build firms face a unique insurance requirement that traditional design-bid-build contractors do not.
General liability insurance covers claims for bodily injury and property damage caused by the physical operations of the business — the construction work performed by the firm’s crews on the job site. If a third party is injured because of a condition created by the construction work, or if the construction process damages adjacent property, GL responds. GL policies contain a professional services exclusion that bars coverage for claims arising from the rendering or failure to render professional services. Design decisions, specifications, and engineering calculations are professional services. When a claim attributes damage to a design error rather than a construction defect, the GL policy’s professional services exclusion applies.
In a traditional design-bid-build project, the architect carries E&O for the design and the contractor carries GL for the construction. Each party’s coverage corresponds to their scope. In a design-build project, both scopes are merged under a single entity. That entity’s GL policy excludes the design exposure, and without E&O coverage in place, the design error exposure is uninsured.
Both policies are required because a design-build claim rarely allocates neatly to one category or the other. A waterproofing failure may involve a design specification error and a construction installation defect. Both policies need to be in place and properly coordinated for the full liability exposure to be covered. When only one policy exists, the other policy’s exclusion defines the coverage gap.

What Triggers an E&O Claim for a Design-Build Contractor?
E&O policies are written on a claims-made basis, which means two things: the policy in force when a claim is first made not when the alleged error occurred is the policy that responds, and coverage ends if the policy lapses or is not renewed after the firm completes the project.
A claim is typically triggered when the project owner or a third party makes a written demand for compensation arising from an alleged professional services failure. In design-build contexts, claims commonly arise during or after construction when: a structural element does not perform as specified; a system fails during commissioning or shortly after occupancy; a code compliance issue discovered during inspection requires design revision and additional construction cost; or a post-occupancy investigation attributes a building defect to a design error rather than a construction defect.
The claims-made nature of E&O creates a specific risk for design-build firms: if the firm completes a project and then allows its E&O policy to lapse — because it has no active projects or because it is between coverage periods — claims that arise from completed projects have no policy to report to. This is the scenario that tail coverage endorsements, also called extended reporting period endorsements, address. A tail provides a window — typically three to five years for construction projects — during which the firm can report claims arising from professional services rendered before the policy lapsed, even though the policy itself is no longer active.
How Much E&O Coverage Does a Design-Build Contractor Actually Need?
E&O limit adequacy depends on the size and complexity of the projects the firm undertakes and the nature of the professional services being provided. Three factors drive the analysis.
The design fee represents the minimum meaningful reference point. A design-build project with a $400,000 design fee component and a $3.6 million construction component has $4 million in total project exposure — but the professional services exposure is specifically tied to the design component. E&O limits should at minimum be sized to address the design fee exposure and the likely cost of the design errors that could arise from the firm’s scope of services.
Project complexity is the more important driver for firms doing technically complex work. A design-build firm working on mixed-use mid-rise construction with concrete structural systems and complex MEP coordination has professional services exposure that is qualitatively different from a firm doing ground-up commercial shell buildings. The nature of the work, the criticality of the structural systems involved, and the potential consequence of a design error all inform appropriate limit selection.
Contract requirements imposed by project owners increasingly specify minimum E&O limits as a condition of contract award. In design-build procurement, owners commonly require $1 million to $5 million in E&O coverage, with larger public projects sometimes requiring limits that match or exceed the design fee. Understanding what the firm’s typical owner clients require before going to market for coverage allows the E&O program to be structured efficiently rather than reactively.
Tooher-Ferraris works with design-build contractors to evaluate E&O exposure, structure coverage that reflects the firm’s actual project mix and complexity, and coordinate E&O with the broader commercial insurance program including GL, umbrella, and builder’s risk. Learn more at https://toofer.com/specialty-programs/ and https://toofer.com/commercial-insurance/.
RIMS, the risk management society, publishes resources on professional liability for design-build delivery at rims.org. The Design-Build Institute of America provides guidance on standard design-build contract insurance requirements at dbia.org.
Frequently Asked Questions
Does my GL policy cover any design-related claims?
Standard commercial general liability policies contain a professional services exclusion that bars coverage for claims arising from design errors, specifications, or professional advice. Some GL policies are endorsed to provide limited coverage for claims where the damage was caused by construction operations even if a design error contributed — but this is not standard and should be confirmed by reviewing the specific policy language, not assumed. For design-build firms, an E&O policy is the only reliable coverage for the design error exposure.
What is the difference between E&O and professional liability insurance?
In the design and construction context, E&O and professional liability are different names for the same product. The term “errors and omissions” is commonly used in technology and some professional services contexts; “professional liability” is the term more commonly used in architecture, engineering, and design-build contexts. The coverage grant, the claims-made structure, and the tail coverage considerations are the same regardless of which term is used.
How long should my E&O tail coverage extend after project completion?
The appropriate tail period depends on the type of projects completed and the statute of limitations applicable to professional liability claims in the relevant jurisdiction. For most commercial construction projects, a tail period of three to five years after substantial completion is the minimum reasonable standard. Projects with long-term performance warranties, complex structural systems, or significant public use exposure warrant consideration of longer tail periods. Consult with your insurance broker about the specific tail requirements for the types of projects your firm completes before allowing an E&O policy to lapse.
Ready to evaluate your design-build E&O program? The team at Tooher-Ferraris has been helping contractors structure complete construction insurance programs since 1932. Contact us today to schedule a no-obligation consultation — https://toofer.com/contact-us/







