Between any two trade packages there is a line, and somebody has to own the work that crosses it. Scope gaps between trade packages appear in the same six places on almost every job, and each one becomes a change order the moment work reaches it.
Why scope gaps between trade packages exist at all
A building is drawn as a whole and bought in pieces. The drawings show a complete assembly. The trade packages divide that assembly into scopes of work, each with its own bidder, its own price and its own understanding of where the work stops.
The division is done by people writing scope descriptions, usually under time pressure, usually working from a template used on the last job. The drawings do not change. The way the drawings are cut into packages does.
A gap appears when two adjacent scope descriptions both stop short of the same piece of work. Neither bidder priced it. Both were reasonable. The drawings showed it clearly, which is why nobody noticed that nobody had claimed it.
An overlap appears when both scopes include the same work. That one is less dangerous, because it costs money twice rather than appearing out of nowhere, and it usually surfaces during buyout.
Gaps do not surface during buyout. They surface when a crew arrives, finds something not in their contract, and stops.
The six places they always appear
1. Structure to enclosure
Embeds, slab edge tolerances, the anchor system for curtain wall or panel. The structural package pours the slab. The enclosure package hangs off it. The embed plates, the edge angle and the tolerance the enclosure needs from the concrete belong to somebody, and frequently to nobody.
2. Enclosure to waterproofing
Where a wall assembly meets a roof, a plaza, a planter or a below grade condition. Two warranties, two subcontractors, one joint. Transitions between different waterproofing systems are the single most expensive gap on this list, because the first evidence of failure is water inside a finished building.
3. Mechanical, electrical and plumbing to structure
Penetrations, sleeves, hangers, supports and fireproofing patched after a penetration is cut. Who cuts, who patches, who fireproofs and who inspects. Four verbs, often three packages.
4. Equipment to the systems that serve it
Owner furnished equipment is the usual culprit, but it happens with contractor furnished equipment too. The unit arrives. Power, data, drainage, supports and final connection each sit in a different package, and the specification that described the unit rarely described all five.
5. Finishes to everything above the ceiling
Access panels, ceiling coordination, and the trim condition where a wall meets a soffit. Individually small. Collectively, on a job with a lot of ceiling, not small at all.
6. Commissioning and closeout
Training, spare parts, attic stock, as-built drawings, operations manuals. Almost always assumed by the owner to be included and frequently excluded by name on the qualifications page.
Why clash detection does not find them
Clash detection compares geometry. It finds a duct passing through a beam, and it is very good at that. It is a spatial test.
A scope gap is a commercial condition, not a spatial one. The embed plate that nobody priced does not clash with anything. It simply is not in any contract. The model is perfectly coordinated and the work is unbought.
This is why a clean clash report is not evidence that the interfaces are covered, and why a constructability and interface review reads the scope descriptions against the drawings rather than running the model. The two exercises answer different questions and neither substitutes for the other.
The test is not whether two objects occupy the same space. The test is whether every object in the drawings appears in exactly one scope of work.
Why the gaps are found late, every time
Three things have to happen before a gap becomes visible, and all three take months.
The packages have to be written. Scope descriptions are produced under buyout pressure, often by different people for different trades, often reusing language from a previous job with a different building. Two adjacent scopes are rarely drafted by the same person on the same afternoon.
The shop drawings have to arrive. Most interface requirements are invisible until a subcontractor details their own work. The curtain wall anchor requirement does not exist until the curtain wall subcontractor draws it, and that is usually well after award.
Somebody has to be standing at the junction. The gap becomes real when a crew reaches the condition, cannot proceed, and asks who owns it. That is the first moment anybody compares two scope descriptions side by side.
By then the packages are awarded, the price is fixed, and the only available instrument is a change order. Nothing went wrong in the ordinary sense. The sequence simply guarantees that the cheapest moment to find the gap has already passed.
The only way to move the discovery earlier is to read the scopes against each other before the awards, which is an hour of reading per interface and costs nothing to act on.
A worked example
Illustrative figures. Not taken from any client project and not a quotation.
A seven story building with a unitized curtain wall. The structural package includes cast in place concrete and the embed plates shown on the structural drawings. The curtain wall package includes the unit, the anchor and installation.
The curtain wall shop drawings, produced after award, require embeds at a spacing and tolerance tighter than the structural drawings showed. The structural package priced the embeds on the structural drawings. The curtain wall package priced anchors assuming embeds meeting its own requirement.
Neither priced the difference. The gap is 340 embeds at a tighter tolerance, plus survey, plus the sequence change to install them before the slab pour rather than after.
Cost of the change order: $310,000. Schedule impact: four weeks on the enclosure sequence, which is on the critical path.
Found before signature, this is a scope clarification costing nothing, because the packages had not been awarded and the requirement could simply be written into the correct one.
Found in month nine, it is a change order and a delay, and the argument about whose drawings governed takes longer than installing the embeds would have.
What to ask for before you sign
- The scope matrix, if one exists, showing every package against every building system.
- Every trade package scope of work, not a summary, for the six interfaces above.
- Written confirmation of who owns each of the six, by package name.
- The exclusions list for each package, read against the drawings.
- The list of owner furnished equipment, with the five connection items named for each.
- What the closeout package includes: training, spares, attic stock, as-builts, manuals.
Where a scope matrix does not exist, that absence is the finding. It means nobody has checked the interfaces as a set, and the six gaps above are open until somebody does. The rest of this ground sits in constructability, scope and design.
What we do
We read every trade package scope against the drawings and write down what nobody has claimed. Each finding names the two packages, the drawing reference and the likely exposure in dollars. It is a commercial reading, not a design review, and we do not redesign anything. The point is to turn a gap into a clarification while it is still free, which is only true before the packages are awarded. The readiness review covers the price side of the same package.
Questions people ask
Is a scope gap the same as a clash?
No. A clash is two objects occupying the same space, which modeling software finds automatically. A gap is work that appears in the drawings but in nobody contract, and it does not clash with anything. A model can be perfectly coordinated while several interfaces remain unbought by any trade.
Who is responsible for scope gaps on a CM at risk job?
It depends on the contract and on how the packages were written, and entitlement is a question for your counsel rather than for us. What is consistent is that gaps found before award cost nothing to fix, and gaps found after award become change orders. The timing decides the price more reliably than the wording does.
How many trade packages does a typical project have?
Enough that the interfaces outnumber the packages considerably. A job with fourteen packages has far more than fourteen boundaries, because systems cross several scopes each. That arithmetic is why the interfaces deserve their own reading rather than being checked package by package.
This is general information about construction contracts and is not legal advice.