Provisional Sums Explained: Why Your Quote Isn’t Always Fixed
In short
A provisional sum is an allowance included in a building quote for work or items that cannot yet be priced exactly, such as tiles not yet chosen or a repair that cannot be seen until opened up. The final cost is adjusted up or down once the actual cost is known.
A provisional sum is a figure in a quotation that is an estimate rather than a fixed price. It is used where something cannot be priced accurately yet: you have not chosen your tiles, the condition of a floor will only be known once it is lifted, or a specialist has not yet quoted. When the real cost is known, the provisional sum is replaced and the contract price moves up or down accordingly.
Why provisional sums are used
Used properly, provisional sums are honest. They allow work to start without waiting for every decision, and they show the client where the price is still open. Typical uses in a London renovation include:
- Client choices not yet made: tiles, sanitaryware, brassware, flooring, kitchen appliances or lighting.
- Hidden conditions: rotten joists, failed lintels, damp or old wiring that only appears once surfaces are removed.
- Third party work: utility connections, specialist glazing or bespoke joinery yet to be priced.
Prime cost sums versus provisional sums
A prime cost (PC) sum usually covers the supply of a specific item, such as “tiles at £60 per square metre”. The fitting is priced; the product allowance is adjusted to what you choose. A provisional sum is broader and can cover work as well as materials. Both should be clearly labelled in the quote.
How provisional sums can catch people out
The risk is not provisional sums themselves but low or vague allowances. A quote that looks competitive because it allows a modest amount for tiles in a high end bathroom will rise once realistic products are chosen. When comparing quotes, add up the provisional sums separately and ask:
- Is each allowance realistic for the standard I want?
- Is it supply only, or supply and fit?
- What happens to the contractor’s overhead and profit if the sum changes?
- How will the final figure be confirmed and approved by me?
Keeping provisional sums under control
The best way to reduce them is to make decisions early. The more products are chosen before the contract, the more of the price becomes fixed. For hidden conditions, a careful survey and opening up a small area can turn an unknown into a measured item. Everything else should be written into the schedule of works with a realistic allowance.
How we handle provisional sums on London’s Prestige projects
Our quotations show every provisional sum on its own line, with a realistic allowance for the standard you have described, so the number you see is the number you can plan around. We help you finalise selections early to fix as much of the price as possible, and if an allowance changes, we show you the actual cost and get your approval before ordering. It is the approach behind finishes like our Campden Hill Road bathroom in Kensington. Read more about our bathroom renovation service, or book a site visit for a clear, itemised quote.
Common questions
Can a provisional sum go down?
Yes. If the actual cost is lower than the allowance, the contract price reduces by the difference. A fair contract adjusts in both directions.
How do I know if my quote has provisional sums?
They should be labelled as provisional, PC sums or allowances. If a quote does not separate them, ask the contractor which items are fixed and which are estimates.
Are provisional sums a sign of a poor quote?
Not at all. A few honest, realistic allowances are normal. Be cautious with quotes that have many vague or unrealistically low allowances, because the final price will rise.