Provisional Sums in Renovation Quotes: What They Mean and How to Control Them
A provisional sum can make an incomplete renovation design look like a complete price. It appears in the quotation and contributes to the headline total, but the final amount may change when the work is properly defined and carried out.
What is a provisional sum?
A provisional sum is an allowance for work that cannot yet be fully described or measured when the quotation or contract is prepared. It may cover concealed structure, drainage, specialist joinery, utility work or finishes that have not been selected. It is an allowance, not a guaranteed final price.
Why do provisional sums appear?
They are common when design is incomplete, surveys have not resolved an existing condition, a specialist has not yet priced a package, or selections such as worktops, sanitaryware and door hardware remain open. Some uncertainty is unavoidable, but much of it can be reduced before contract by completing surveys, designs and selections.
Defined and undefined allowances
A defined allowance has enough information about the nature, location, indicative quantity and constraints of the work for the contractor to plan it sensibly. An undefined allowance is materially uncertain in scope, extent, method or access. The contract wording determines the practical consequences, so these labels should not be used casually.
What happens when the work is instructed?
A well-managed process identifies the allowance, completes the missing design or investigation, obtains a written quotation, omits the original allowance and adds the properly valued work. The project team should record any related overheads, profit, preliminaries, tax and programme effects under the signed contract.
An allowance is not a price cap
If a quotation includes a £10,000 provisional sum, the final cost may be lower, equal to or higher than that figure. Ask whether the allowance includes supply, installation, waste, access, protection, design, attendance, overheads, profit, testing and tax. A bare number is not a useful risk description.
Compare quotations on a like-for-like basis
Before ranking competing bids, list every allowance, match equivalent work, check what sits inside and outside each figure, and normalise the bids using a common reasonable allowance. A lower tender may simply contain lower assumptions for unresolved work. Keep provisional sums separate from client contingency and from later variations.
How to reduce the risk before signing
Complete drawings and schedules as far as practical. Make priority selections. Use targeted opening-up, drainage surveys, structural inspections and electrical assessments to convert unknowns into measurable work. Obtain specialist budgets for bespoke joinery, glazing, stone, mechanical systems or heritage work. State who owns each design decision and when it must be resolved.
Require written instructions and forecasts
Before provisional work proceeds, request a written scope, quantities, labour and material breakdown, supplier quotation, overheads and profit, preliminaries or attendance, tax, programme impact, validity and exclusions. Track the original allowance, amount omitted, instructed value, paid amount, remaining commitment and forecast final cost.
Common mistakes
Treating the headline total as fixed, using round figures with no scope, confusing a product allowance with installed cost, allowing too many incomplete selections, spending without written approval, ignoring programme consequences and failing to reconcile unused sums can all undermine the budget.
Questions to ask before signing
Ask why each allowance is provisional, what information would firm it up, whether labour and materials are included, how overheads and tax are treated, who can authorise expenditure, what the decision deadline is and how underspend, overspend and time effects will be valued.
The bottom line
Provisional sums are useful when uncertainty is genuine and visible. Reduce uncertainty through design, surveys and selections; describe what remains; use realistic amounts; set decision deadlines; require written instructions; and reconcile each allowance transparently.
Ask our team to review the drawings, specification, quotation and provisional-sum schedule before the building contract is signed.
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