Provisional Sums and PC Sums in a Builder's Quote, Explained

You open a quote and see "Provisional sum £3,500" or "PC sum £2,000 for sanitaryware". It looks like a price. It is not. It is an allowance, and the final bill moves when the real cost is known.

This page explains provisional sums and PC (prime cost) sums in plain English, how they differ, and what to ask before you treat a quote as fixed.

Quick answer

• A provisional sum is a placeholder for work or costs that are not fully defined yet (often foundations, drainage, or making good after opening up).
• A PC sum (prime cost sum) is usually an allowance for a defined type of item you will choose later (tiles, sanitaryware, a kitchen, ironmongery), typically for supply, with fitting priced separately or alongside.
• Neither figure is a fixed price. If the real cost is higher, you usually pay the difference (and any agreed attendance or margin).
• Add up every provisional and PC sum. If they are a large share of the total, the "fixed" quote is not really fixed.
• Ask how each allowance was set, what happens if it is underspent, and whether the builder's margin is inside or on top.

A quote with big provisional sums is not really a fixed price. For £59 I'll tell you which allowances look light. Review my builder's quote, £59

Provisional sum: what it means

A provisional sum covers work the builder cannot firm up yet. Common examples on home jobs:

• Foundations "as required" once ground conditions are known
• Drainage alterations after a survey or CCTV
• Structural steel once the engineer has final sizes
• Asbestos removal if suspected but not sampled
• Making good in adjoining rooms once finishes are stripped

The builder puts in a reasoned guess. You pay the actual cost of that defined provisional item once it is known, according to the contract wording. See also the foundations example in our example quote review.

PC sum (prime cost): what it means

A PC sum is usually for choosing products later. For example:

• £2,500 PC for bathroom sanitaryware
• £80/m² PC for floor tiles
• £6,000 PC for a kitchen supply

Often the quote prices labour to fit separately (or includes fitting) and leaves the supply as a PC allowance you can spend up or down by choosing different products. Read the wording: some builders put margin inside the PC, some add attendance on top when you pick.

Provisional vs PC: quick comparison

Australian and Malaysian pages online blur these terms. On UK domestic quotes, the split above is what I usually see, but always read that builder's definitions on the page.

Does a provisional sum include the builder's margin?

Sometimes yes, sometimes no. Ask:

• Is the provisional sum for net cost only, with overhead and profit added later?
• Or is it an all-in allowance?
• If underspent, do you get the saving back?
• If overspent, is there a written variation before work continues?

If the answer is vague, the allowance is not ready to accept.

How much provisional is too much?

There is no single legal percentage. As a sense-check:

• A few defined provisional items on a complex refurb can be normal.
• If a large share of the headline price is allowances, you do not yet have a fixed price for the job.
• Light provisional sums (obviously too low for the work described) are a sales tactic: the bid looks cheap, then rises.

Add them up with the quote comparison tool. Pair that with a sensible contingency you hold yourself.

Big provisional sums on your quote? Send it over. For £59 I'll say which allowances look light and what to ask each builder. Review my builder's quote, £59

What to ask before you sign

1. Please list every provisional and PC sum and what each covers.
2. How was each figure calculated?
3. What happens if it is under or overspent?
4. Is your margin included?
5. Can any of these be firmed up before we start (investigations, samples, locked specs)?
6. Will every overspend be priced and agreed in writing before the work?

Red flags

• One large "provisional" pot with no breakdown
• Foundations, drainage and steel all provisional on a job where neighbours have recent similar builds and open information exists
• PC sums that would only buy the cheapest possible finish when the drawings show high spec
• No process for agreeing overruns
• Calling the whole job "fixed price" while half of it is allowances

The short version

Provisional and PC sums are allowances. Add them up, test whether they are realistic, and do not treat the headline total as fixed until they are defined or clearly bounded. The less detail in the quote, the more contingency you need to hold.

Want the allowances checked?

I've been a builder for nearly 30 years. For £59, send me up to three quotes for one job. I'll flag light provisional sums, unclear PC allowances and what to firm up before you sign. Written review and a call within 24 hours.

Review my builder's quote, £59 · See an example review · Compare quotes free