Scheduling

What is a preliminary schedule in construction?

A preliminary schedule is an early, summary-level timeline that sets the major phases and milestones of a project before the detailed baseline schedule is built.

Two construction professionals review paper plans beside a tablet at a jobsite workbench.
Plan reviews connect field conditions, drawings, and the next decisions on a job. AI-generated illustration.

A preliminary schedule is the first credible answer to the owner's question: how long will this take? It is built from incomplete information, usually during design, budgeting, or bidding, and it shows big blocks of work rather than every activity. Once the contract is signed and the design is far enough along, it is replaced by a detailed baseline schedule.

Owners use it to plan financing, leases, and move-in dates. Contractors use it to price time-related costs such as supervision, trailers, and equipment.

What it usually includes

  • Design and permitting durations, if they are still ahead.
  • Procurement of long-lead items like switchgear, elevators, and rooftop units.
  • Major construction phases: sitework, foundations, structure, envelope, rough-in, finishes.
  • Key milestones: notice to proceed, dry-in, permanent power, substantial completion.
  • Owner activities such as furniture, IT, and move-in.
  • Stated assumptions, such as work hours, weather allowance, and permit timing.

Some owners and contracts require a short-term schedule for the first weeks of work, submitted soon after award, while the full baseline is developed. If your contract has that requirement, the preliminary schedule must meet its specific format and deadline.

How it works on a real job

Say a design-build contractor is pricing a 30,000-square-foot warehouse with a small office. Design is at 30 percent. The owner needs the building by the end of the third quarter to meet a lease. The contractor's preliminary schedule shows 10 weeks of design completion and permitting, 6 weeks of sitework, 8 weeks of foundations and slab, and the pre-engineered metal building delivered 16 weeks after order.

That last line drives everything. If the building order waits until the permit is in hand, steel arrives late and the lease date is missed. So the schedule shows an early release of the metal building order, which the owner approves with a separate early-procurement agreement. The contractor also flags that the timeline assumes a typical permit review, so a slow review is the owner's risk.

The same schedule also shapes the price. Because the field duration is about 22 weeks, the estimator carries roughly five months of superintendent time, trailer rental, and temporary utilities in general conditions. If the owner later asks to compress the timeline, the preliminary schedule is the starting point for pricing overtime or added crews.

Common mistakes

  1. Treating it as a promise. Write the assumptions on the schedule so nobody holds you to dates built on a 30 percent design.
  2. Leaving out procurement. Lead times for equipment often control the finish date more than field work does.
  3. Forgetting owner tasks. Owners delay jobs too, through slow decisions and late owner-furnished items.
  4. Never replacing it. A preliminary schedule used as the job schedule has no logic to measure delays against.
  5. Pricing general conditions on an optimistic duration.

Related terms

See construction schedule, progress schedule, critical path method, and Gantt chart. For building the detailed version, read how to build a construction schedule.

Frequently asked questions

How detailed should a preliminary schedule be?

Detailed enough to show major phases, long-lead procurement, and milestones. A few dozen lines is common. Too much detail on an incomplete design just creates false precision.

Is a preliminary schedule part of the contract?

Sometimes. Some contracts attach it as an exhibit or require one soon after award. Read how the contract treats it, and state your assumptions.

What replaces the preliminary schedule?

The baseline schedule, which is a detailed, logic-driven schedule accepted by the owner and used to measure progress and delays.

Written and edited by

Maurice Francois writes and edits construction operations guides for Smart Business Automator. More from Maurice on the Scaling Legends podcast.

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