How to Resolve Sub Scope Overlap Before It Becomes a Change Order

The concrete sub thinks the equipment pads are in his scope. The mechanical sub’s proposal excludes them. Both are right according to their own documents, and neither is wrong, you just forgot to assign the work to anyone specific. That’s how a $22,000 change order gets born on a job that was already bought out tight.

Scope overlap is not a subcontractor problem. It’s a GC coordination problem, and it almost always traces back to the bid phase, where nobody had time to reconcile the edges.

The Same Gaps, The Same 40 Years

The dangerous zones are predictable once you’ve been through a few buyouts. Mechanical and electrical fight over equipment connections: who runs the whip, who provides the disconnect, who does the final hookup. Concrete and structural steel argue about embed plates and anchor bolts. Drywall and painting disagree about who patches after the electricians. Fire protection and plumbing overlap at drain points and sleeves in rated assemblies.

None of this is obscure. These same gaps have been generating change orders for 40 years. The reason they keep appearing is that scope sheets are written per trade, not across trades. Each sub is responsible for their column. Nobody owns the intersections.

The structural tells are in the exclusions. A mechanical proposal that says “electrical connections by others” and an electrical proposal that says “equipment hookups by mechanical” means the final connection to that unit belongs to nobody. You’ll find out in month seven when the equipment startup is scheduled and the argument starts about who’s pulling the wire the last six feet.

Catch It Before the PO Is Cut

The window is narrow. After you’ve received bids and before you award, you have maybe a few days where you can actually fix this without it costing anyone money. Once the PO is cut, the sub’s scope is locked, and any clarification becomes a negotiation.

Read every exclusion list against the other trades. This is not a quick process, a commercial project with 18 sub scopes has a matrix of potential overlaps that takes real time to work through. But the alternative is a buyout meeting six months later where two subs are both pointing at the same work and neither is planning to move.

Build a simple overlap log. It doesn’t need to be elaborate: a spreadsheet with four columns works fine, work item, sub A’s position, sub B’s position, assigned to. Go line by line through the high-risk interfaces. Mechanical/electrical is always the sharpest edge. Civil/concrete, concrete/steel, drywall/acoustical, and plumbing/fire protection follow closely. The CSI MasterFormat division structure is useful here: when two divisions share a boundary, that boundary is where the overlap lives.

Call the subs before award. Not to renegotiate price, to confirm scope. “Your proposal excludes equipment pads. I’m reading that as concrete’s responsibility. Can you confirm that’s your understanding?” Most subs will confirm or flag the issue right there. The ones who get quiet or say “we’d need a CO for that” are telling you exactly what you need to know.

Do not wait for the preconstruction meeting to have this conversation. By then the budget is fixed, the schedule is set, and nobody wants to absorb a scope they weren’t counting on, and treating the preconstruction meeting as a scope-reconciliation session is a mistake that costs real money. The bid phase is when you have options.

One Sub, One Exhibit, No Ambiguity

Once you’ve identified the overlap, pick one sub and put it in writing. Not in an email that says “we discussed”, in the subcontract exhibit. The scope exhibit is the document that matters. If the work isn’t in the exhibit, it doesn’t exist.

The language matters. “Mechanical contractor to provide and install all equipment pads per structural drawings, including formwork, concrete, anchor bolts, and grouting” leaves no room for interpretation. “Equipment pads by mechanical” will generate a question on day one of the job.

If neither sub priced the work, you have a gap, not an overlap, and that’s a different problem with its own math. Somebody is absorbing cost that wasn’t in anyone’s number. At that point you’re deciding whether to go back to one of the subs and negotiate it into their scope, carry it in your self-perform budget, or take the hit in contingency. Whatever you do, decide it consciously. The worst outcome is discovering the gap at startup and funding it with money you didn’t plan for.

The subs who perform well on coordination are the ones who own their edges. A good mechanical sub knows where his scope ends and electrical’s begins, and he’ll tell you in plain language. That clarity, or the absence of it, shows up in how they write their proposals. It’s one more signal worth reading before you sign the PO. For more on reading those signals early, see how to read a subcontractor bid for red flags before you call them.

Comms Center logs every conversation with every sub in one searchable thread, so when a scope clarification happens over the phone at 4:30 PM, it’s documented and attached to that sub’s record, not buried in someone’s inbox. When the PM asks at buyout whether the equipment pad was discussed, the answer is findable. Learn more at commscenter.com.