What is a schedule of works?

Three documents, three jobs

JCT's practice note says Minor Works is not suitable where bills of quantities are required. For a typical extension or refurbishment, the choice is between a specification, a schedule, or the two together.

Where there are no quantities, the risk of mismeasurement moves to the contractor. JCT's practice note warns that tenders may rise to cover the contractor's preparation costs and possible disputes over the quantity of work the documents imply. A clear schedule reduces both.

How the schedule is priced and used

JCT's MW 2024 user checklist lists the documents that describe the work (contract drawings, contract specification, work schedules) and the pricing document the contractor provides: a priced specification, priced work schedules, or a schedule of rates. Whichever you choose becomes part of the contract.

That matters later. JCT's comparison of its contracts shows that Minor Works has no detailed rules for valuing variations. When you add a window or drop a rooflight, the rates in the priced schedule are the obvious evidence of what the change is worth. A schedule priced as one lump sum per room gives the contract administrator much less to work with than one priced line by line.

What to put in a schedule of works

RICS NRM 2 lists the sections of a bill of quantities. Adapted for a schedule, they give this checklist:

1. Preliminaries. Site set-up, access, security, safety, protection of the parts of the house you are living in, skips, temporary services, and your requirements at completion.
2. Demolition and strip-out.
3. The work itself, in the order it is built: below ground and drainage, structure, roof, windows and doors, internal walls, services, finishes, external works.
4. Making good where new meets old.
5. Provisional sums, each described as fully as you can.
6. Work the contractor designs, if any, with the requirements it must meet.
7. Dayworks, the rates for work valued on time and materials.
8. A summary that carries every section to a total.

Each item should point to the drawing or specification clause that describes it. An item that says only "new kitchen" invites six different prices for six different kitchens.

Provisional sums

NRM 2 defines a provisional sum as money set aside for work that cannot be fully described and quantified under its rules, and splits them in two:

• Defined. The work is not completely designed, but you can state its nature and construction, how and where it fixes to the building, a quantity showing its scope, and any limits. The contractor is assumed to have allowed for it in its programme, planning and preliminaries.
• Undefined. Any of that information is missing. The contractor is assumed to have made no allowance, so the work can bring extra time and preliminaries with it.

NRM 2 also says provisional sums should exclude overheads and profit, which are dealt with separately. JCT's practice note confirms that work under a provisional sum is valued using the priced document.

For example, "Provisional sum of £4,000 for underpinning 6 m of the rear wall to a depth of 1.5 m, if trial holes show it is needed" is close to defined. "Provisional sum £4,000, structural works" is undefined.

Prime cost sums

NRM 2 defines a PC sum as a supply-only rate included in a unit rate for materials or goods whose exact quality is not yet known. Its own examples are facing bricks at £480 per 1,000 and ceramic wall tiles at £50 per square metre. The sum excludes fixing, sundries, and the contractor's preliminaries, overheads and profit, which are priced separately in the rate. When you choose a tile at £70 per square metre, the difference in supply cost is adjusted under the contract.

Do not confuse a PC sum with a prime cost contract. JCT uses "prime cost" for contracts paid on actual cost plus a fee, which its practice note calls a relatively high-risk option for the client where the extent of the work is not known.

What this means for you

Three things make a schedule useful: it covers every item on the drawings, each item is specific enough that two contractors would price the same thing, and provisional sums are defined wherever they can be. A contingency is your own allowance for the unknown and sits outside the schedule. A provisional sum is a named item inside it.

Parallel Architecture writes schedules of works and specifications for tender: see tender and contract administration.