How Do You Build a Construction Schedule?

The estimate already breaks the job into scopes that someone priced: the bid packages, the general conditions, the self-performed work. Use that breakdown as the schedule's structure (the general contractor's guide shows where the schedule sits between buyout and mobilization, and the project lifecycle shows the whole job). Phases become the summary rows (sitework, foundations, structure, envelope, interiors, closeout), and each priced scope becomes one or more activities under them. When the schedule and the estimate share a breakdown, a slip in an activity points at a company and a contract, and a change order lands on a line you can find.

Split each scope by area or floor until no activity is longer than the contract allows. The Corps of Engineers' guide specification for project schedules, UFGS 01 32 01.00 10, caps construction activities at "20 workdays or 30 calendar days" (§3.3.2), so that progress can be measured between update periods. It is a good rule on private work too. For the field, a three-week look-ahead breaks these activities down further, to pieces a foreman can staff.

1. List the activities by phase and area from the estimate. Name each one so a sub reads it the same way you do: "Stem walls, area A", not "Concrete 2".
2. Size each duration from its quantity: the takeoff quantity divided by what the crew installs in a day, rounded up to whole working days. Ask the sub who priced it what crew size they carried.
3. Link the activities. Most links are finish-to-start; use start-to-start with a lag where trades overlap (tape can follow hanging by a few days). Every activity needs a predecessor and a successor except the first and the last.
4. Add procurement: each critical submittal, its review, fabrication and delivery. UFGS 01 32 01.00 10 calls out "long lead" items with "an anticipated procurement sequence of over 90 calendar days" (§3.3.4).
5. Add the activities nobody prices but everyone waits on: owner and agency approvals, permits, utility tie-ins, inspections, commissioning, punch-list correction, O&M manuals and as-built drawings (the guide spec lists these in §3.3.5 and §3.3.6).
6. Set the calendar: the work week, holidays and any weather allowance your contract defines. Durations and float are counted in working days on that calendar.
7. Calculate the critical path and float, read it, and fix what looks wrong. Then walk it with the major subs, adjust, and save the agreed version as the baseline.

A fictional one-story clinic, Fernhill Medical, with the durations from the table and a 30-working-day steel procurement (shop drawings, review, fabrication and delivery). Day 1 is the first working day after notice to proceed. A forward pass gives each activity its earliest start and finish; a backward pass from the end gives its latest finish; float is the difference.

The foundations and slab total 3 + 8 + 4 + 3 = 18 days, but steel erection waits for the steel, which arrives after day 30. So the critical path runs through procurement: 30 + 6 + 8 = 44 days to dried-in, and the slab chain has 12 days of float. That changes what the project manager does in week one: push the steel shop drawings, not the concrete. A schedule that left procurement out would show the slab on the critical path and a dried-in date on day 32, 12 days too early.

• Open ends. UFGS 01 32 01.00 10 allows only two: the first activity has no predecessor and the last has no successor (§3.3.11). Any other dangling activity has float that means nothing.
• Constraints in place of logic. A date typed into an activity hides why it starts then. Use a link, and keep constraints for real outside dates such as an owner move-in.
• Lags used as durations. The same guide spec says lags must not be "used in place of realistic original durations" (§3.3.16). If concrete has to cure, say so in a note and keep the lag honest.
• Missing owner work. Furniture, IT, owner-supplied equipment and inspections by others belong in the network; they are often the reason a turnover date slips.
• A float total that looks too good. If most of the job has weeks of float, look for missing links.

Public contracts set the deadline. Where the federal schedules clause applies, FAR 52.236-15 asks for "a practicable schedule" within five days after work commences, "or another period of time determined by the Contracting Officer". Private contracts usually set their own date; read the general conditions. Once it's issued, owners read it the way our guide on how an owner reads a schedule describes.

In Conflo's schedule the GC builds phases, tasks and milestones, links them finish-to-start, start-to-start, finish-to-finish or start-to-finish with a lag in days, and sets the project's work week and holidays. Float and the critical path are calculated from the dates on the schedule, counting working days only, and a loop of links is refused. When a predecessor slips, linked work that hasn't started moves later; nothing is pulled earlier on its own.

If you build schedules in Microsoft Project or Primavera P6, import the XML export instead of retyping it (Conflo vs Microsoft Project covers what comes across). When the team agrees on the schedule, Save baseline copies the dates as the yardstick for slippage.

A buildable schedule comes from the estimate: priced scopes split into activities of 20 working days or less, durations from crew output, every activity linked, and procurement in the network.

Run the critical path before you trust a finish date. On many jobs a long-lead item, not the concrete, decides it.

See the schedule in Conflo

1. UFGS 01 32 01.00 10, Project Schedule (August 2026), §3.3.2, §3.3.4, §3.3.5, §3.3.6, §3.3.11 and §3.3.16 — U.S. Army Corps of Engineers (Whole Building Design Guide). Read October 22, 2026.
2. FAR 52.236-15, Schedules for Construction Contracts — Acquisition.gov (General Services Administration). Read October 22, 2026.