How to Add an Additional Insured to Your Contractor Insurance Policy

Every subcontract you sign will require it. Every GC will ask for it. The certificate of insurance they want shows it. But many contractors don't fully understand what "additional insured" status actually means — or what the difference is between a blanket endorsement and a scheduled one, between CG 20 10 and CG 20 37, or between primary/non-contributory language and standard coverage language.

Understanding these distinctions matters. Getting them wrong means your COI says one thing but your policy says something different — and when a claim happens, the coverage isn't there. This guide walks through everything you need to know.

What Additional Insured Status Actually Means

When you name someone as an additional insured (AI) on your general liability policy, you're extending your policy's protection to cover them — but only for claims that arise from your work or operations. Here's the critical nuance:

• What it covers: If you install defective plumbing and a GC gets sued, your policy defends the GC and pays any covered damages — because the claim arose from your operations.
• What it does NOT cover: If the GC does something wrong that's unrelated to your work and gets sued, additional insured status on your policy does not protect them. They're covered for claims arising from YOUR work, not their own independent negligence.
• Defense costs: One of the most valuable aspects of AI status is that it gives the additional insured access to your carrier's defense — legal representation — even before a claim is resolved. Lawsuit defense costs in construction disputes routinely run six figures.

Why GCs Require It

General contractors carry their own GL insurance. So why do they need to be on your policy too? Because vicarious liability. When you're working under a GC and something goes wrong, the injured party often sues everyone — the GC, the sub, the owner, and anyone else with deep pockets or an insurance policy. The GC's liability for your work is real, and their insurer doesn't want to be the one paying for it when you were the one doing the work.

By requiring AI status on your policy, the GC ensures that if they get dragged into a lawsuit arising from your operations, your carrier handles the defense and payment — not their carrier. This protects the GC's own loss history and keeps their premiums from being affected by claims that were really your fault.

How to Request an Additional Insured Endorsement

The process is straightforward:

1. Contact your broker — call or email us with the request. You don't call the insurance carrier directly; your broker handles it.
2. Provide the AI's full legal name and address — exactly as it needs to appear on the endorsement. Get this from the GC's contract or their certificate request. "ABC Construction" is not the same as "ABC Construction, Inc." for endorsement purposes.
3. Provide the contract language — send us the insurance section of the subcontract so we know exactly what endorsement forms are required (CG 20 10, CG 20 37, blanket AI, primary/non-contributory, waiver of subrogation).
4. We add the endorsement and issue the COI — same day in most cases. The updated certificate is sent electronically to whoever needs it.

The ISO Endorsements: CG 20 10 vs CG 20 37

The Insurance Services Office (ISO) publishes standard endorsement forms that the industry uses. For additional insured coverage on GL policies, two forms are most common:

CG 20 10 — Additional Insured, Ongoing Operations

This endorsement extends AI coverage to the named party for liability arising out of your ongoing operations. It covers claims that happen while you're actively working — during the project. If a visitor trips over your tools on an active job site and sues the GC, CG 20 10 protects the GC under your policy.

CG 20 37 — Additional Insured, Completed Operations

This endorsement extends AI coverage for liability arising from your completed work. Construction defect claims — leaks, structural failures, faulty installations — often surface months or years after project completion. CG 20 37 protects the GC for those post-completion claims. California's statute of limitations for latent construction defects runs 10 years, making completed ops coverage critical.

Blanket AI vs. Scheduled AI Endorsements

There are two ways to add additional insured coverage to your policy:

Scheduled Additional Insured

Each AI is individually named in an endorsement attached to your policy. This is more precise — you can specify different terms for different AIs — but requires a separate endorsement for each party, which means you need to contact your broker every time you take on a new GC or project.

Blanket Additional Insured

A blanket AI endorsement automatically extends additional insured status to any party required to be an AI by written contract with you. If your contract requires you to add XYZ Development as AI, the blanket endorsement covers them without a separate endorsement filing. This is much more efficient for contractors who work with multiple GCs or developers.

Blanket AI endorsements typically cost $100–$300/year added to your policy premium. For contractors who regularly work with different GCs, it's almost always worth it. We recommend building blanket AI language into every contractor GL policy we write.

Primary and Non-Contributory Coverage

Standard AI endorsements don't automatically make your policy respond first if both your policy and the GC's policy could apply to a claim. GC contracts almost always require "primary and non-contributory" language to address this.

Primary: Your policy responds before the additional insured's own insurance.

Non-contributory: Your policy doesn't require the GC's insurer to share in the claim — your policy pays without seeking contribution from the GC's carrier.

Without primary and non-contributory language, your carrier and the GC's carrier may dispute who pays what percentage of a claim, delaying resolution and creating friction. GCs require primary/non-contributory to ensure their own insurance isn't drawn into claims arising from their subs' work. This typically requires a separate endorsement — confirm with your broker that it's in your policy.

Waiver of Subrogation

Subrogation is your insurance carrier's right to sue a third party who caused the loss to recover what they paid you. A waiver of subrogation means your carrier gives up that right against a specific party.

Example: Your carrier pays a $50,000 claim for water damage caused by your crew. Normally they could sue the GC if the GC was partially responsible. A waiver of subrogation in favor of the GC means your carrier can't pursue the GC.

Waiver of subrogation must be in place before the loss occurs. It cannot be added retroactively. Most GC contracts require it. We add it by endorsement — confirm it's there when you review your certificate.

What Additional Insured Endorsements Cost

The good news: individual AI endorsements are typically inexpensive.

• Scheduled AI endorsement (per party): $0–$50 in most cases
• Blanket AI endorsement: $100–$300/year added to policy premium
• Primary and non-contributory endorsement: Often included with AI endorsement or small additional charge
• Waiver of subrogation endorsement: Typically $50–$150/year blanket, or per-project at low cost

The COI Cannot Create Coverage That Doesn't Exist

A certificate of insurance is evidence of insurance — it documents what your policy provides. It is not the policy itself, and it cannot create coverage that the policy doesn't actually have. This is one of the most common and costly misunderstandings in contractor insurance.

Always verify with your broker that the endorsements shown on the COI are actually reflected in your policy. This is our job — and we make sure the policy matches what the contract requires before we issue the certificate.

Frequently Asked Questions