Professional Liability Insurance for Architects and Engineers

Architects and engineers need professional liability insurance because a design error can lead to costly rework, delays, or property damage claims long after a project is finished. Washington and Idaho licensing laws do not require it for architects or engineers, but owner and design-build contracts often do: a Washington state design-build project we reviewed required $2 million per claim and coverage renewed for five years after completion.

By Trella Commercial · Updated October 24, 2026

The short version

Licensing laws do not require it in Washington or Idaho for architects, engineers, or land surveyors. Contracts do.
Claims arrive late. Construction-related claims against designers can accrue up to six years after completion in both states, and the time to file suit runs from there, and design claims can surface well after the work.
Some owner contracts set long requirements. A Washington state design-build project required design E&O of $2 million per claim and $4 million aggregate, renewed for five years after completion.
General liability does not cover design errors. Washington's state contracting guidance notes that general liability policies exclude professional liability.
Retirement needs planning. Because coverage is usually claims-made, retiring or closing a firm without a tail can leave past projects uninsured.

Licensing rules in Washington and Idaho

Profession	Washington	Idaho
Architects	No professional liability requirement in chapter 18.08 RCW	No requirement for architects in Idaho Code chapter 54-3
Engineers and land surveyors	No requirement in chapter 18.43 RCW	No requirement in the engineer and surveyor law (Idaho Code chapter 54-12)
Interior designers	Not reviewed in this guide	A certified interior designer filing technical submissions for a building permit must give the building official proof of professional liability insurance in force (Idaho Code 54-306)

How long design claims can last

State	Rule for design and construction of improvements to real property
Washington	Claims must accrue within six years after substantial completion or the end of services, whichever is later (RCW 4.16.310). Negligence claims generally then have three years (RCW 4.16.080), and Washington courts often start that clock at discovery
Idaho	Tort claims accrue no later than six years after final completion of construction, and contract claims accrue at final completion; the normal limitation period then runs (Idaho Code 5-241)

This is why some owner contracts require design E&O for years after completion, and why a firm's tail coverage matters when partners retire. See tail coverage.

What owner and design-build contracts require

Requirement	Example
Limits	Design E&O of $2,000,000 per claim and $4,000,000 aggregate (Washington DES design-build project 2023-166)
Post-completion coverage	Renewed for five years after final completion (same project)
Additional insured	Professional liability carved out of the additional insured requirement (same project)
Subconsultants	Check whether the contract requires your structural, MEP, or civil subconsultants to carry their own E&O

Paste your owner agreement into our contract insurance checker to see every requirement.

Practice policies and project policies

Option	How it works	When it fits
Practice policy	One annual policy covering all of the firm's projects, sharing one aggregate	A firm's ongoing work under one annual limit
Project-specific policy	A separate limit dedicated to one project, which can run through completion plus a stated period after	Large projects, or when an owner requires dedicated limits

Common gaps

A tail too short for the six-year construction periods when a firm closes or a partner retires
A retroactive date that does not reach back to older projects after switching insurers
Contracts that require longer post-completion coverage than the firm planned for
Subconsultants without adequate coverage, whose errors become your claim
Design-build roles, where the firm takes on contractor-type risk the practice policy may not cover
Defense costs inside the limits on a policy sized close to the contract minimum

Also see general contractors for the construction side, and how much E&O you need.

Common questions

Do architects need professional liability insurance in Washington?

Not by law. Chapter 18.08 RCW does not require it. Owner contracts, public projects, and design-build agreements often do, often for years after completion.

Do engineers need professional liability insurance in Idaho?

Not by Idaho's engineer and surveyor licensing law. Contracts often require it. Idaho does require certified interior designers filing technical submissions for a building permit to show proof of professional liability insurance.

How long after a project can an architect or engineer be sued?

In Washington, claims must generally accrue within six years after substantial completion or the end of services, whichever is later, and then must be filed within the applicable limitation period. In Idaho, tort claims accrue no later than six years after final completion.

Does general liability cover design errors?

Generally no. General liability is built for bodily injury and property damage from your operations, and Washington's state contracting guidance says CGL policies exclude professional liability. Design errors are a professional liability claim.

Sources

This guide is general information, not legal advice. Coverage depends on the policies actually issued. Reviewed October 2026.

More in this guide

Professional Liability (E&O) Insurance for Washington and Idaho Businesses
The complete guide this page is part of.
Professional Liability Insurance for Consultants
Professional liability and errors and omissions (E&O) insurance for consultants and advisors in Washington and Idaho: what it covers, what client and government contracts require, how much to carry, claims-made and tail coverage, AI-assisted work, and what else consultants usually need.
How Much Does Professional Liability (E&O) Insurance Cost?
What drives the cost of professional liability and errors and omissions (E&O) insurance for Washington and Idaho businesses: your profession and services, revenue, limits and deductible, claims history, contract requirements, retroactive date, defense terms, and how to lower the premium without losing coverage.
Claims-Made vs Occurrence Insurance: What Is the Difference?
The difference between claims-made and occurrence insurance policies, with examples: retroactive dates, prior acts, extended reporting periods (tail), switching insurers, retiring or closing a business, how Washington courts treat late notice under claims-made policies, and which business policies use which form.
Tail Coverage (Extended Reporting Period) for Professional Liability
What tail coverage, or an extended reporting period, is and when you need it: closing, selling, or retiring from a business, switching insurers, and contracts that require it. How long a tail to buy in Washington and Idaho, and what a tail does and does not cover.
How Much Professional Liability (E&O) Insurance Do I Need?
How to choose professional liability (E&O) limits: per claim and aggregate limits, what Washington and Idaho contracts and rules require, defense costs inside or outside the limits, deductibles, limitation of liability clauses, and when $1 million is not enough.
Professional Liability vs General Liability: What Is the Difference?
The difference between professional liability (E&O) and general liability insurance: what each covers, real examples, why general liability excludes professional mistakes, claims-made vs occurrence, additional insured differences, and why most service businesses and client contracts need both.
Tech E&O Insurance for Software, SaaS, and IT Companies
Technology errors and omissions (tech E&O) insurance for software, SaaS, and IT companies in Washington and Idaho: what it covers, how it combines with cyber, what state and client contracts require, limits, claims-made terms, AI features, and common gaps.
Insurance for Independent Contractors, Freelancers, and 1099 Consultants
Insurance for independent contractors, freelancers, and 1099 consultants going out on their own in Washington and Idaho: professional liability (E&O), general liability, cyber, workers comp rules for sole proprietors, what client contracts require, and how coverage moves with you from employee to business owner.
My Contract Requires Professional Liability (E&O) Insurance. What Now?
What to do when a client contract, MSA, or government solicitation requires professional liability or errors and omissions (E&O) insurance: reading the limits, claims-made and tail terms, insurer rating, additional insured, certificates, real Washington and Idaho examples, and how to get covered before work starts.
Insurance for Marketing, Advertising, and Creative Agencies
Insurance for marketing, advertising, design, and creative agencies in Washington and Idaho: professional liability (E&O) for campaigns that miss, media liability for copyright and defamation claims, why general liability may not cover an agency's advertising work, AI-generated content, client data and cyber, and what client contracts require.
Which Professions Must Carry Professional Liability Insurance in Washington and Idaho?
Which professions Washington and Idaho law requires to carry professional liability or errors and omissions (E&O) insurance, or to disclose that they do not: lawyers, real estate licensees, escrow agents, structural pest inspectors, interior designers, and the professions with no requirement, including architects, engineers, CPAs, home inspectors, appraisers, and insurance agents.
Waiver of Subrogation Explained
What a waiver of subrogation is, why contracts and leases require it, how it works on general liability, auto, property, and workers comp, the endorsement you need, how Washington's state-run workers comp changes the picture, and how it differs from waiving workers comp immunity.
Additional Insured Explained
What additional insured means, why clients, general contractors, and landlords require it, the endorsement you need (ongoing and completed operations, blanket or scheduled), why a certificate alone is not enough, primary and noncontributory wording, which policies it applies to, and real Washington and Idaho contract examples.

Find out what your current policies actually cover.

Send us what you have. We review it line by line against your leases and contracts, and tell you plainly what is missing. Free, and no obligation.

Get a free policy review Call (425) 537-7773