When a plumbing contractor subs under a general contractor, the subcontract does not just describe the work — it dictates the insurance the sub has to carry, and it comes with a demand for proof. For a plumbing business bidding commercial and new-construction jobs, understanding those requirements is the difference between mobilizing on schedule and getting held up at certificate time. This post walks what a general contractor typically requires from a plumbing sub and how to read the requirement against your own policy.
The short version: the requirements almost always include general liability at a stated limit, additional-insured status on that general liability, a certificate of insurance proving it, workers compensation, and commercial auto — with an umbrella, a waiver of subrogation, and primary-and-noncontributory wording added on larger jobs. The additional-insured guide owns the endorsement mechanics; this post is the owner’s-eye view of the whole insurance exhibit and how to satisfy it.
Where the requirements live: the subcontract insurance exhibit
The insurance a general contractor requires is not a conversation — it is a written exhibit attached to the subcontract, the master services agreement, or the purchase order, and it is paired with a demand for a certificate of insurance evidencing every item on it. What a plumbing contractor has to understand is that this exhibit is a checklist the GC will actually verify: its compliance team reads the certificate and the endorsements against the exhibit line by line, and any mismatch stops the file. Reading that exhibit early — before signing, not when the certificate request lands mid-job — is the single most useful habit for a sub that works under general contractors, because it turns a potential job-stopping gap into something handled on your own timeline. On larger general contractors the review is not even a person you can call — it runs through a third-party compliance portal that checks the certificate and the endorsement forms against the exhibit automatically and flags anything that does not match. That makes the exhibit less a negotiation than a specification: the coverage either matches what is written or the file does not clear. The plumbing contractors who move fastest treat the insurance exhibit the way they treat a plan set — as a document to read and build to before the work starts.
General liability and the additional-insured demand
At the center of almost every exhibit sits general liability at a stated limit, paired with a requirement that the general contractor be named an additional insured on it. Additional-insured status extends part of your general liability to the GC for liability connected to your plumbing work, and a careful contract asks for it on both your ongoing operations while the crew is on the job and your completed operations after the plumbing is signed off — usually the CG 20 10 and CG 20 37 endorsements that the additional-insured guide walks in full. The point an owner cannot miss is that the status is granted by the endorsement on your policy, not by the certificate that references it, and that completed-operations piece is the one most often left off. A plumbing sub’s long water-damage tail is exactly why the GC wants the completed-operations status, so it is worth confirming both endorsements are attached rather than assuming the pair is there.
The certificate is the evidence, not the coverage
The most expensive misunderstanding in the whole exchange is treating the certificate of insurance as the coverage. It is not. A certificate is a snapshot that evidences coverage was represented on a given day; the coverage itself lives in the policy and the endorsements attached to it. A general contractor that collects a certificate and files it has proof that coverage was represented — not the additional-insured status, the waiver, or the limits the exhibit demanded. For a plumbing contractor, the practical consequence is that a clean-looking certificate does not mean the underlying endorsements are actually on the policy, and the honest move is to confirm the endorsements exist and reach the operations the contract requires before relying on the certificate to close the file. There is a second wrinkle worth knowing: a certificate can be issued showing coverage that a later policy change quietly removed, and it can name limits the underlying policy does not actually carry to the general contractor. Neither the plumbing sub nor the GC is well served by a certificate that overstates the program, because the gap only surfaces when a claim tests it. The discipline that protects both sides is the same — the endorsements and limits are confirmed on the policy first, and the certificate is issued to reflect what is genuinely there.
Workers comp, auto, and the rest of the exhibit
Beyond general liability, the exhibit reaches the rest of your program. Workers compensation is nearly universal, because the general contractor does not want your injured crew members reaching back to it — and many project owners require comp regardless of state rules. Commercial auto covers the trucks and vans your crews drive to and around the site, and the exhibit usually sets a limit for it. On larger jobs the requirements climb: an umbrella or excess policy to reach a higher total limit than the primaries carry, a waiver of subrogation so your insurer gives up its recovery rights against the GC, and primary-and-noncontributory wording so your policy answers first without calling on the GC’s own coverage. Each of these is granted by policy wording or an endorsement — not by the certificate — so each is another line to confirm against your actual program rather than assume.
Real-World Scenario: A plumbing contractor wins a commercial build-out under a general contractor and signs the subcontract without reading the insurance exhibit closely. On mobilization day the GC’s compliance team rejects the certificate: the general-liability limit is fine, but there is no completed-operations additional-insured endorsement, no waiver of subrogation, and the umbrella limit is short of the requirement. The crew sits while the plumbing contractor scrambles to have the endorsements added and the limit raised mid-job — slower and costlier than it would have been up front. A second sub on the same project read its exhibit before signing, arranged the endorsements and the umbrella in advance, and mobilized on schedule. Same requirements; the one who read them early started on time.
Waiver of subrogation and primary-and-noncontributory: the terms owners miss
Two phrases in the exhibit trip up more plumbing contractors than any others, because they sound like boilerplate and are not. A waiver of subrogation means your insurer agrees, in advance, to give up its right to come after the general contractor to recover what it paid on a claim — even a claim the GC had a hand in. Carriers do not grant that automatically; it takes policy wording or an endorsement, and some charge for it. Primary-and-noncontributory is really two requirements in one: your policy must respond first, and it must do so without asking the general contractor own policy to contribute. Together they push the financial weight of a covered claim onto your program rather than the GC, which is exactly why general contractors ask for the terms and verify the wording is actually attached. For a plumbing sub the rule is the same one that governs the additional-insured endorsement: these are policy terms, not certificate boxes, so confirm your carrier has agreed to them before you certify compliance — not after a claim reveals the wording was never there.
Match your program to the contract before you sign
The takeaway is straightforward: a general contractor’s insurance requirements are a checklist it will verify, the coverage that satisfies them lives in your policy and its endorsements rather than the certificate, and the completed-operations additional-insured piece and the higher-limit and waiver terms are the ones most often missed. Read the insurance exhibit against your own program before you sign, confirm the endorsements are attached and the limits are met, and handle any gap on your timeline instead of the project’s. The additional-insured guide walks the endorsement mechanics in detail, and the commercial plumbing work where these demands concentrate is exactly where an early read pays off. When you are ready, start a quote and send us the contracts you are bidding, or browse the coverage overview to see how the lines the exhibit asks for fit together. The habit costs a few minutes at bid time and saves a stalled crew at mobilization; on a trade that lives on commercial and new-construction work under general contractors, it is one of the cheapest forms of loss control an owner has.