2.5 Project Management, Scheduling & Field Supervision
Key Takeaways
- The critical path is the longest continuous chain of dependent activities through a network, and it alone sets the project duration; activities on it have zero total float.
- Total float is how long an activity can slip without delaying project completion, computed as late start minus early start.
- Submittals and shop drawings must be approved before fabrication or ordering, and long-lead mechanical equipment is the most common source of schedule failure on HVAC work.
- Delays are classified as excusable and compensable, excusable but non-compensable, or non-excusable, and the classification determines whether the contractor gets time, money, both, or neither.
- Closeout is a deliverable: as-built drawings, operation and maintenance manuals, test and balance reports, warranty letters, and owner training all condition final payment.
2.5 Project Management, Scheduling & Field Supervision
[!NOTE] Scope of this subject area: On the Alabama HAC blueprint, project management is a small but reliably tested block. Questions center on scheduling arithmetic (critical path and float), the submittal and request-for-information workflow, and who owns a delay. This section teaches those three ideas plus the documentation habits that decide whether a delay claim survives.
The Phases of a Mechanical Project
| Phase | Contractor deliverable | Typical failure |
|---|---|---|
| Preconstruction | Reviewed drawings, RFIs on conflicts, buyout of equipment | Ordering before submittal approval |
| Submittals | Product data, shop drawings, coordination drawings | Long-lead gear submitted last |
| Rough-in | Duct, refrigerant lines, condensate, gas, sleeves, hangers | Missed sleeve or a chase closed by another trade |
| Equipment set | Curbs, rigging, crane pick, unit set and secured | Crane scheduled before roof curb is flashed |
| Trim and start-up | Grilles, thermostats, controls, start-up report | Start-up before permanent power |
| Test, adjust, balance | TAB report against design airflow | Balancing a system with unfinished ceilings |
| Closeout | As-builts, O&M manuals, warranties, training | Retainage held for a missing manual |
Submittals, Shop Drawings and RFIs
- A submittal proves the product you intend to install matches the specification. Product data sheets, performance curves, and electrical data are submitted, reviewed by the engineer, and returned marked approved, approved as noted, revise and resubmit, or rejected.
- Shop drawings are the contractor's own fabrication drawings - duct layouts at scale, hanger details, seismic or wind restraint details. Nothing should be fabricated from a design drawing alone.
- A request for information (RFI) is the written mechanism for resolving a drawing conflict. Verbal answers do not change the contract. Number every RFI, log the date asked and the date answered, and note whether the answer changed cost or time.
- Coordination drawings overlay mechanical, electrical, plumbing, and fire protection in the same ceiling space. The trade that coordinates last usually pays for the rework.
Critical Path Scheduling
A critical path method (CPM) schedule is a network of activities with durations and dependencies. Four numbers are computed for each activity:
- Early start (ES) and early finish (EF) from a forward pass.
- Late start (LS) and late finish (LF) from a backward pass.
- Total float = LS - ES = LF - EF.
The critical path is the longest continuous path through the network. Every activity on it has zero total float; a one-day slip on any of them slips the project one day.
Worked Example
A small rooftop replacement has these activities:
| Activity | Duration | Depends on |
|---|---|---|
| A - Permit and submittals | 10 days | - |
| B - Equipment lead time | 25 days | A |
| C - Curb fabrication | 6 days | A |
| D - Roof curb set and flash | 3 days | C |
| E - Crane pick and unit set | 1 day | B, D |
| F - Electrical and controls tie-in | 4 days | E |
| G - Start-up and TAB | 3 days | F |
Path 1: A + B + E + F + G = 10 + 25 + 1 + 4 + 3 = 43 days. Path 2: A + C + D + E + F + G = 10 + 6 + 3 + 1 + 4 + 3 = 27 days.
The project duration is 43 days and the critical path runs through equipment lead time. Activities C and D carry 43 - 27 = 16 days of total float: the curb can be fabricated and set any time in a sixteen-day window without moving the completion date. Expediting the curb saves nothing. Expediting the equipment order is the only action that shortens the job - which is why long-lead equipment is released first on every well-run mechanical project.
Look-Ahead Planning and Field Supervision
- Three-week look-ahead: the master CPM schedule is strategy; the rolling look-ahead is execution. It names crew, material, equipment, and the predecessor each activity is waiting on.
- Daily report: date, crew and hours, weather, work performed, deliveries, visitors, inspections, delays and their cause. A contemporaneous daily report is the evidence that wins a delay claim two years later.
- Productivity tracking: compare actual hours per unit installed against the estimated labor unit weekly, not at the end. A crew running 20% over on week one will be 20% over on week ten.
- Punch list: walk the job with the owner and generate the list yourself before the architect writes one.
Who Owns the Delay
| Delay classification | Time extension | Additional money | Example |
|---|---|---|---|
| Excusable and compensable | Yes | Yes | Owner-directed change, late owner-furnished equipment, defective design |
| Excusable, non-compensable | Yes | No | Unusually severe weather, strike, act of government |
| Non-excusable | No | No | Contractor's own late ordering, undermanning, rework |
Contract notice provisions are strict. Most construction contracts require written notice of a delay or a claim within a stated number of days of the event, and courts routinely enforce the deadline. Give notice in writing, on time, even when relations are good.
Closeout: The Package That Releases Retainage
- As-built (record) drawings marked with every field change.
- Operation and maintenance manuals with model and serial numbers, filter sizes, wiring diagrams, and parts lists.
- Test, adjust and balance report demonstrating design airflow at each outlet.
- Start-up reports signed by the technician, with refrigerant charge method and readings.
- Written warranties from the contractor and from the manufacturer, with start dates.
- Owner training with a signed attendance record.
- Final lien waivers from the contractor and every supplier and subcontractor.
In a mechanical project schedule, activity "Curb fabrication" has an early start of day 11 and a late start of day 27. What is its total float, and what does that mean for the project completion date?
A rooftop unit arrives three weeks late because the contractor released the purchase order after rough-in instead of at submittal approval. Under standard delay classification, what relief is the contractor entitled to?
Why does a well-run mechanical contractor process the submittal for long-lead rooftop equipment before the submittal for sheet metal fittings?