A good building quote is itemised: it breaks the price into stages and trades (preparation, foundations, structure, roof, glazing, electrics, plumbing, plastering, finishes), lists what is excluded, identifies any provisional sums, states whether VAT is included, and is tied to drawings and a specification. A lump sum quote gives one figure, which is hard to compare and hard to adjust when something changes. Ask for an itemised quote, compare quotes line by line, and agree in writing how changes (variations) will be priced.
Key takeaways
- Itemised quotes make comparison fair and changes transparent.
- Exclusions and provisional sums explain most of the difference between quotes.
- A quote should be based on the same drawings and specification for every builder.
- Payment stages should follow completed work.
- The quote becomes part of the written contract.
01Itemised vs lump sum
| Itemised quote | Lump sum quote | |
|---|---|---|
| What you see | Price for each stage or trade | One total |
| Comparing builders | Line by line | Total only |
| Changes during the build | Priced from known rates | Harder to value fairly |
| Spotting omissions | Easy | Difficult |
| Trust | Shows the builder has priced the detail | Can hide gaps |
Swipe the table sideways to see every column.
02What a good quote includes
- Your details, the address and the date.
- The documents it is based on: drawing numbers, structural calculations, specification.
- A description of the scope in plain language.
- An itemised breakdown, for example:
– site set-up, protection and waste removal; – demolition and strip-out; – excavation, foundations and drainage; – walls, steelwork and structure; – roof, rooflights and weatherproofing; – windows and doors; – electrics, plumbing and heating; – plastering, screeds and floors; – kitchen or bathroom installation; – joinery, decorating and making good.
- Provisional sums with an explanation of how each was estimated.
- Prime cost (PC) sums for items you will choose later, such as tiles or sanitaryware.
- Exclusions, stated clearly.
- VAT, shown separately.
- Programme and expected start date.
- Payment stages.
- Validity period of the quote.
03Provisional sums and PC sums explained
- Provisional sum: an allowance for work that cannot be priced exactly yet, for example drainage until the drains are exposed. The final cost may change.
- Prime cost (PC) sum: an allowance for an item you will choose, for example “£X per m² for floor tiles”. If you choose a more expensive product, the price rises.
Many provisional sums mean a less certain price. Read our guide to hidden costs of building work.
04How to compare quotes
- Make sure every builder prices the same drawings and specification.
- Put the quotes side by side, line by line.
- Check exclusions and add their cost to the cheaper quotes.
- Compare provisional and PC sums and adjust them to the same allowance.
- Compare programmes and payment stages.
- Consider experience, references and communication, not just price. See our guide on how to choose a builder.
05Payment stages
Payments should follow progress. A typical pattern links payments to stages such as foundations complete, structure complete, roof and glazing complete, first fix complete and practical completion, with a final payment after snagging. Avoid paying large sums before work is done.
06Variations: when things change
Changes happen, for example a different kitchen layout or extra sockets. The contract should say:
- how a variation is requested and confirmed in writing;
- how it is priced, ideally from the rates in the itemised quote;
- how it affects the programme.
07How Prohaus quotes
Every Prohaus project starts with a conversation and a site visit, followed by a detailed and transparent itemised quotation for the agreed scope. The work then runs under a written, agreed contract, and completed work has a 1-year guarantee. See our guide prices on the services page and our house extension cost guide.
08Frequently asked questions
Why are builders’ quotes so different?
Usually because of different scope, specification, exclusions or provisional sums. Compare them line by line on the same drawings.
Should I accept a quote without a site visit?
For anything structural, no. Structure, access, drainage and the condition of older houses need to be seen.
Is a fixed-price quote better?
A fixed price is only as reliable as the scope it covers. A clear itemised quote with few provisional sums gives more certainty than a “fixed price” with vague scope.
How long is a quote valid?
The quote should state its validity period, because material prices change.
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About Prohaus
Prohaus Ltd is a building company based in Kingston upon Thames, registered in 2015 and built on more than 20 years of residential building experience. We carry out extensions, loft conversions, renovations, new builds, kitchens and bathrooms, glazing, bespoke joinery and garden offices across Kingston, Surbiton, Richmond, Barnes, Putney, Fulham, Chelsea, Clapham and Wimbledon. Every project runs under a written contract with a 1-year guarantee.
Get an itemised quote
Send us your address, drawings and what you want to achieve. We will visit and provide a written, itemised quotation.
