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, including design decisions, specifications, calculations, drawings, and professional advice that form part of a design-build project. When a claim alleges that a design error, specification issue, or professional judgment caused damage or financial loss to a project owner or third party, E&O coverage is generally the policy designed to respond.
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 generally covers claims for bodily injury and property damage arising from the physical operations of a business, including construction work performed by the firm’s crews on a job site. If a third party is injured because of a condition created by the construction work, or if construction activities damage adjacent property, GL coverage may respond.
GL policies typically contain a professional services exclusion that limits coverage for claims arising from the rendering or failure to render professional services. Design decisions, specifications, and engineering calculations generally fall within the scope of professional services. When a claim attributes damage to a design error rather than a construction defect, the GL policy may not respond because of the professional services exclusion.
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 structure of E&O coverage creates a specific risk for design-build firms. If a firm completes a project and later allows its E&O policy to lapse, whether because it has no active projects or is between coverage periods, claims arising from completed projects may have no active policy under which to be reported. Tail coverage endorsements, also known as extended reporting period endorsements, are designed to address this risk. A tail endorsement provides a reporting window, often three to five years for construction projects, during which the firm can report claims arising from professional services provided before the policy lapsed, even though the policy is no longer active.
How Much E&O Coverage Does a Design-Build Contractor Actually Need?
There is no single E&O limit that fits every design-build contractor. The right amount depends on the firm’s professional services, project mix and contract requirements. Three factors should guide the review.
1. The potential cost of a design error. A design fee is a useful measure of the services performed, but it is not a ceiling on a claim. On a $4 million project with a $400,000 design fee, an error could lead to redesign, construction rework, delays or other alleged losses that exceed the fee. Evaluate the possible consequences of an error in the firm’s actual scope of work when selecting a limit.
2. Project complexity. Structural systems, mixed-use occupancy and complex mechanical, electrical and plumbing coordination can increase the potential severity of a professional liability claim. Consider the largest and most technically demanding projects the firm takes on, along with whether claims from multiple projects could draw on the same annual policy limit. irmi.com
3. Owner contract requirements. Review proposed insurance terms before bidding or signing. Required limits, the length of time coverage must remain in place and the insurance carried by design consultants can all affect the program. The Design-Build Institute of America’s sample insurance exhibit provides spaces for the parties to specify insurance types and limits; it does not prescribe one limit for every project. store.dbia.org
E&O should also be reviewed alongside general liability, umbrella and builder’s risk coverage. Those policies address different exposures, and an umbrella should not be assumed to increase the E&O limit. Tooher-Ferraris helps contractors evaluate their project mix and coordinate coverage through its specialty programs and broader commercial insurance services. Tooher-Ferraris
Is your E&O limit appropriate for the projects you are pursuing? Contact Tooher-Ferraris to schedule a no-obligation consultation.
Frequently Asked Questions
Does my GL policy cover any design-related claims?
Standard commercial general liability policies typically contain a professional services exclusion that limits coverage for claims arising from design errors, specifications, or professional advice. Some GL policies may include endorsements that provide limited coverage when construction operations cause damage, even if a design error also contributed to the loss. However, this is not standard and should be confirmed by reviewing the specific policy language rather than assumed.
For design-build firms, E&O coverage is specifically designed to address professional liability arising from design services and related errors or omissions.
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.















