CG 20 10 vs. CG 20 37: The Additional Insured Endorsement Gap That Leaves GCs Uncovered

5 days ago

6 min read

Almost every general contractor requires subcontractors to name them as an "additional insured" on the sub's general liability policy before work starts — but a surprising number of GCs never check which specific endorsement form actually accomplishes that, and the gap between the two most common forms, ISO CG 20 10 and CG 20 37, can be the difference between real coverage and a false sense of security. CG 20 10 covers ongoing operations while the subcontractor's work is in progress; CG 20 37 extends that coverage to completed operations after the work is finished. A GC holding only a CG 20 10 endorsement from a sub has no additional insured protection at all for a claim that arises after that sub's work wrapped up — exactly the kind of claim that construction defect and completed-operations liability most commonly produces.

What "Additional Insured" Status Actually Does

Being named as an additional insured on a subcontractor's general liability policy means the GC gets direct access to that policy's coverage and defense for claims arising out of the subcontractor's work, rather than relying solely on an indemnification clause in the subcontract and the sub's financial ability to make good on it. This matters enormously in practice: an indemnification clause is only as valuable as the indemnifying party's ability to pay, while additional insured status puts the GC in direct contractual privity with an insurance carrier that has the financial resources to actually pay a claim and the contractual obligation to defend it. For a GC relying on dozens of subcontractors across a project, additional insured status converts an informal risk-transfer hope into an enforceable insurance relationship.

CG 20 10 ("Additional Insured — Owners, Lessees or Contractors — Scheduled Person or Organization") covers the additional insured for liability arising from the named subcontractor's ongoing operations performed for that additional insured — but, depending on the specific edition, generally does not extend to claims arising after the subcontractor's work on the project is complete.
CG 20 37 ("Additional Insured — Owners, Lessees or Contractors — Completed Operations") specifically extends additional insured status to completed operations liability — claims arising after the subcontractor's work is finished, which is exactly when many construction defect, property damage, and injury claims actually surface, sometimes years after substantial completion.
A GC that requires only CG 20 10 from subs, without also requiring CG 20 37 (or a combined endorsement that covers both ongoing and completed operations), has a coverage gap precisely where it matters most — many construction liability claims, from water intrusion to structural defects, don't surface until well after the sub has demobilized from the job.
Some ISO endorsement editions and some carriers offer a single combined form providing both ongoing and completed operations additional insured coverage — contractors should specifically confirm which edition and which combination of forms a sub's certificate actually reflects rather than assuming "additional insured" on a certificate means comprehensive protection.

Why a Certificate of Insurance Alone Doesn't Prove Anything

A standard certificate of insurance (ACORD 25 is the most common form) is a convenient summary, but it's explicitly not a contract and carries no binding obligation on the insurer — a certificate can show "additional insured" checked without specifying which endorsement form actually provides that status, and in the worst cases, a certificate can be issued showing coverage that was never actually bound on the underlying policy. The only way to confirm what additional insured protection actually exists is to request and review the actual endorsement itself (not just the certificate referencing it), confirming the specific ISO form number and edition date, and ideally reviewing it alongside legal counsel or a knowledgeable insurance broker before relying on it for a significant project.

Primary and Non-Contributory Language Matters Just as Much

Beyond which endorsement form is used, the "primary and non-contributory" wording attached to it determines whose insurance actually pays first when a claim hits. Without this specific language, a sub's additional insured coverage for the GC can end up contributing alongside the GC's own liability policy on a pro-rata basis, rather than responding first and exclusively — meaning the GC's own policy, and its own claims history and premium, absorbs part of a loss that the risk-transfer arrangement with the sub was specifically designed to avoid. Requiring "primary and non-contributory" language as part of the additional insured requirement, not just additional insured status alone, closes this gap and is now standard practice among contractors who've had this exposure explained to them by their own insurance counsel, usually after discovering it the hard way.

Equipment and Rental Scenarios Add Another Layer

Additional insured requirements extend beyond labor subcontractors into equipment rental and transportation arrangements as well — a contractor renting equipment with an operator, or hiring a trucking company to haul materials or equipment, typically needs to be named as an additional insured on that vendor's liability policy too, following the same ongoing-versus-completed-operations and primary-and-non-contributory logic. This is easy to overlook because equipment rental and hauling arrangements often move faster and feel more transactional than a formal subcontract, but the liability exposure from an equipment-related incident or a trucking accident can be just as significant as from any labor subcontractor's work, if not more so given the severity potential of heavy equipment and vehicle incidents.

Waiver of Subrogation Is a Related but Separate Requirement

Alongside additional insured status, many construction contracts also require a waiver of subrogation — a separate provision preventing a sub's insurer from paying a claim and then turning around to sue the GC (or another party on the project) to recover what it paid out, essentially closing off a second avenue of liability exposure between parties who are supposed to be protecting each other, not litigating against each other after an insurer pays a claim. Waiver of subrogation and additional insured status address different exposure and often appear as separate contract clauses and separate policy endorsements, so a contractor checking for one should specifically check for the other as well rather than assuming a certificate showing additional insured status automatically covers subrogation waiver too — the two frequently travel together in a well-drafted risk transfer program, but neither one implies the other exists on its own.

A Worked Example: The Completed-Operations Claim Nobody Was Covered For

Illustrative example, not an actual case: a general contractor requires every subcontractor to provide a certificate showing the GC as an additional insured, and a roofing sub provides exactly that — a certificate referencing a CG 20 10 endorsement, properly in force while the sub was actively working on the project. Eighteen months after project completion, a roof leak traced back to the sub's installation work causes significant interior water damage, and the building owner sues the GC. When the GC turns to the roofing sub's liability policy for defense and coverage as an additional insured, it discovers that CG 20 10 alone doesn't extend to this completed-operations claim — the sub never carried CG 20 37, and nobody on the GC's team had checked for it at the time the certificate was collected. The GC ends up defending and potentially paying the claim largely on its own, exactly the outcome its additional insured requirement was supposed to prevent.

Building a Verification Process, Not Just a Collection Process

Most contractors already collect certificates of insurance from every sub and vendor before work starts — the gap is almost always in verification, not collection. A stronger process requires the actual additional insured endorsement (not just a certificate referencing it) for any subcontractor whose work carries meaningful completed-operations exposure, confirms both CG 20 10-equivalent and CG 20 37-equivalent coverage (or a combined form covering both) is in force, confirms primary and non-contributory language is included, and tracks policy expiration dates through the full period the completed-operations exposure realistically extends — which, for construction defect claims, can be years beyond substantial completion depending on the applicable statute of repose in the relevant state.

How This Connects to Equipment Financing

A contractor's own equipment financing and insurance programs run on the same logic as additional insured requirements for subs — a lender financing equipment typically wants to be named as a loss payee or additional insured on the borrower's own equipment insurance, for exactly the same risk-transfer reasons a GC wants it from a sub. BFC finances the excavators, loaders, and trucks construction businesses depend on, and understanding how additional insured coverage actually works protects a contractor on both sides of that relationship — as the party requiring it from subs, and as the party potentially providing it to a lender. Our piece on

the workers' comp premium audit and uninsured subcontractor exposure covers a closely related subcontractor-documentation risk worth reviewing alongside additional insured verification. Our piece on buying an existing contracting business and UCC lien due diligence covers another area where verifying the actual documentation, not just a summary of it, matters just as much.

The Bottom Line

Requiring additional insured status from subcontractors is only as protective as the specific endorsement form behind it, and a GC holding only ongoing-operations coverage (CG 20 10) with no completed-operations extension (CG 20 37) has no protection at all for the construction defect and property damage claims that most commonly surface after a project wraps up. Contractors who verify the actual endorsement form and edition, require primary and non-contributory language, and extend the same scrutiny to equipment rental and hauling vendors are closing a gap that otherwise surfaces, expensively, at exactly the moment a GC most needs the coverage to be real.