Most coordination tools track clashes. This one tracks the conditions that make clashes inevitable — and the sequence of decisions that prevents them.
It manages the pre-construction BIM coordination process from kickoff through fabrication release — organized around areas of the building, the disciplines working in each one, and the specific constraints that must be resolved in the right sequence.
A coordination project is a series of interdependent decisions. The wrong decision made first forces every decision that follows to work around it. The right sequence — defined by the physics of the building, not by schedule convenience — is what this tool enforces.
The tracker holds the complete coordination state of the project: which systems are defined, which trades are responsible for them, which areas of the building require coordination, what constraints exist in each area, what state those constraints are in, and who committed to what in each week's coordination cycle. That information is stored in a single .vdcpt file that travels with the project, can be shared, archived, and opened by any team member.
When trades begin resolving clashes before all discipline models are loaded, they are solving problems against an incomplete picture. Solutions become provisional. When the missing elements arrive, every resolved clash must be re-checked. The cost is not just time — it is the erosion of team trust in the coordination process itself.
No area can enter coordination until every expected discipline has confirmed their elements are loaded at the required level of development, a five-point checklist is satisfied, and the VDC manager has signed off. The gate is structural — not a suggestion. Coordination that starts before it passes is flagged as premature and scored accordingly.
Gravity drainage, structural clearances, and existing conditions are not negotiable. They constrain everything that follows. The tier system encodes this reality — T0 and T1A constraints must be resolved before T3 coordination can produce reliable solutions. Resolving in the wrong order produces solutions that look right until the element they ignored shows up.
Every week's trade commitments are logged against specific constraints and attributed to specific contacts. At end of week, the VDC manager commits the week — freezing a permanent snapshot that can be saved as its own file. The report emails directly from the commit, listing every trade's resolved, activated, and pending items with contact names.
Loading and coordination are different activities with different completion criteria. They must be kept separate. Mixing them is the most common source of rework in pre-construction coordination.
Loading phase — every discipline expected in this area submits their elements at the required level of development. The VDC manager tracks loading per discipline, monitors confidence levels, and runs the loading gate checklist. The gate has five criteria: all disciplines confirmed, minimum confidence met, no unverified T1 or T1A elements, gravity drainage path modeled, and VDC manager sign-off. Nothing in the loading phase is about solving — it is about confirming that the problem is fully visible.
80% complete — one criterion remaining. Coordination is locked until the gate is passed.
Coordination phase — constraints are resolved in tier order. T1 and T1A constraints set the immovable boundaries. T3 constraints are resolved within those boundaries. T4 fills in what remains. The coordination phase is locked until the loading gate passes. If coordination has already started in an area where loading is incomplete, the system flags it as premature coordination — risk score is multiplied by 1.8 and all resolved constraints are marked provisional until loading completes and the gate is passed.
Premature coordination is the most expensive mistake in pre-construction. A team that coordinates 80% of an area's clashes before all disciplines have loaded will likely re-coordinate 60% of those solutions when the missing elements arrive. The loading gate exists to prevent this.
Not all constraints are equal. Some are set by physics, regulation, or existing conditions and cannot move. Others are preferences that can adapt. Coordinating preferences before resolving the immovable constraints produces solutions that must be undone.
| Tier | Category | Who controls it | Rule |
|---|---|---|---|
| T0 | Absolute fixed | Regulatory / legal authority | Cannot be changed under any circumstance. Municipal utility inverts, code-mandated clearances, property line setbacks. Establish these before the project starts. |
| T1 | Structural primary | Structural EOR | Requires EOR approval and structural drawing revision to change. Beam depths, slab penetration locations, column positions. Resolve before any MEP routing. |
| T1A | Gravity drainage spine | Plumbing EOR / Civil EOR | Physics-constrained. Every foot of horizontal run consumes irreversible vertical drop. The full slope path — roof drain to stack to underground invert — must be modeled at building scale before any ceiling coordination begins. Three audit checkpoints: shaft turn, mid-run, terminal invert. |
| T2 | Fixed program | Owner / PM | Requires owner decision to change. Room dimensions, ceiling height commitments, program areas. Establish before primary MEP. |
| T3 | Primary MEP distribution | MEP subs and EORs | Largest systems at full size — duct mains, pipe mains, bus duct, FP mains. Coordinate before secondary MEP. Duct main elevation sets everything below it. |
| T4+ | Secondary MEP, architectural | All trades | Branch ductwork, branch piping, conduit home runs, devices, ceiling grid. Coordinate within the envelope established by T1 through T3. |
Gravity drainage deserves its own tier — T1A — because it is not structural and it is not MEP. It is physics. A roof drain leader descending at 1/8 inch per foot over 140 feet of horizontal run consumes 17.5 inches of vertical drop before it reaches the stack. That number is fixed at the moment the stack location is set. Every duct, pipe, and conduit that runs parallel to that leader in the ceiling plenum must fit within what remains above the leader's invert. Getting the leader elevation wrong, or not modeling it at all before ceiling coordination begins, is the single most common cause of late-stage rework in commercial office buildings.
The tracker follows the natural sequence of a pre-construction coordination project. Each step builds on the one before. Skipping steps is visible in the data.
All views read from and write to the same .vdcpt project file. Switching between them is switching context, not switching tools.
Files: The project saves as .vdcpt (VDC Phase Tracker) — a JSON file that does not conflict with any Windows application. Each committed week saves as a separate ProjectName-weekN-committed.vdcpt file. Both can be opened in any text editor, version-controlled in Git, and shared without any installation required. The tracker itself is a single HTML file that runs in any browser with no server.