If you are a roofing contractor working for general contractors or property owners, you will be asked to provide additional insured endorsements on virtually every commercial project. The two most commonly required ISO forms are CG 20 10 and CG 20 37, and understanding the difference between them is essential because using the wrong one — or missing one entirely — can get your certificate of insurance rejected and delay your project start.
CG 20 10: Ongoing Operations
The CG 20 10 endorsement adds a party (typically the GC or property owner) as an additional insured on your GL policy for claims arising from your ongoing operations — meaning work you are currently performing. If your crew is tearing off an old roof and debris falls onto a pedestrian, the GC named on your CG 20 10 is protected under your policy for that claim. This endorsement is active while you are on the job site performing work.
The key limitation is timing. CG 20 10 covers only claims that occur during your active operations. The moment you complete your scope and leave the project, this endorsement stops providing additional insured coverage. For a roofer, that means a leak that develops six months after you finish the job is not covered for the additional insured under CG 20 10 alone.
CG 20 37: Completed Operations
The CG 20 37 endorsement extends additional insured coverage to claims arising from your completed work. This is the endorsement that protects the GC or owner when a roof system you installed fails after project completion. If you welded a TPO membrane in March and a seam failure causes interior water damage in November, CG 20 37 ensures the additional insured has coverage under your policy for that claim.
For roofing contractors, this endorsement is arguably more important than CG 20 10 because the most expensive claims — wind uplift failures, membrane defects, flashing failures, ponding water damage — typically manifest months or years after you leave the site.
Why GCs Require Both
Sophisticated general contractors and their risk managers require both CG 20 10 and CG 20 37 because they need protection during construction (ongoing operations) and after turnover (completed operations). The AIA A401 subcontract form and most custom subcontract insurance requirements now explicitly list both endorsement numbers. If your certificate of insurance shows only CG 20 10, expect the GC to reject it and demand the completed operations form before releasing your first payment.
Edition Dates Matter
Both endorsements have been revised over the years, and the edition date changes the scope of coverage. The 2004 editions (CG 20 10 04 13 and CG 20 37 04 13) are the most widely accepted and provide broader coverage than earlier versions. Some older editions of CG 20 10 included both ongoing and completed operations, but the current versions split them into separate forms. If a GC's contract specifies a particular edition date, your broker must attach that exact version. Using a different edition can create a coverage mismatch that surfaces at the worst possible time — during a claim.
Proprietary vs. ISO Forms
Some carriers do not use ISO standard forms and instead issue proprietary additional insured endorsements. These can be narrower than the ISO versions, sometimes limiting coverage to specific job sites, capping the additional insured's coverage at a sublimit, or including restrictive language that effectively negates the endorsement. If your carrier uses a proprietary form, have your broker compare it line by line against the ISO versions. Many GC risk managers will reject proprietary forms outright and require manuscript endorsements matching ISO language.
Cost and Availability
Adding both CG 20 10 and CG 20 37 to your policy typically costs $500 to $2,000 per year, depending on your carrier and how many additional insureds you schedule. Some carriers include blanket additional insured coverage, which automatically extends the endorsements to anyone you are contractually required to name, without scheduling each party individually. Blanket forms save administrative time and prevent gaps when you start a new project before the endorsement paperwork is processed.
Never assume your policy includes these endorsements. Pull your endorsement schedule, verify the form numbers and edition dates, and confirm both ongoing and completed operations are covered.