Choose a builder who has done similar work locally, gives an itemised written quotation, works under a written contract, can show insurance, uses registered trades for gas and electrical work and explains who handles building control and party wall notices. Ask to see similar finished projects, agree a staged payment schedule linked to completed work, and get the guarantee in writing. Avoid anyone who asks for a large payment upfront or will not put the scope in writing.
This checklist applies to extensions, loft conversions and renovations anywhere in south-west London. Below each question we explain what a good answer looks like, and how Prohaus answers it.
Key takeaways
- Get at least two or three quotes, and compare them line by line, not just the total.
- The contract matters as much as the price: scope, price, programme, payments, variations and guarantee.
- Check the company on Companies House and verify registrations on the official registers.
- Local experience with your house type reduces surprises.
- Clear communication during the quote is a good sign of communication during the build.
01The 12 questions
1. Have you built projects like mine nearby?
Why it matters: A builder who knows Victorian terraces, 1930s semis and the Royal Borough of Kingston upon Thames’s planning approach will price more accurately and spot problems earlier.
Good answer: Named local examples with photos, and similar house types.
Prohaus: We are based in Kingston. Recent projects include a wrap-around extension on Barnfield Avenue, a rear extension on Staunton Road and a loft conversion with a new kitchen on Grange Road, Chessington. See our Kingston page and Projects.
2. Will you visit the property before quoting?
Why it matters: Structure, drainage, access and the condition of older houses cannot be priced from photos alone.
Good answer: Yes, with questions about the structure, services and access.
Prohaus: Every quotation follows a site visit, where most older-house surprises are found early.
3. Is the quotation itemised?
Why it matters: A single lump sum hides what is included. An itemised quote lets you compare builders fairly and control changes.
Good answer: Separate lines for preparation, foundations, structure, roofing, glazing, electrics, plumbing, plastering, finishes and any provisional sums, with exclusions listed.
Prohaus: We provide a detailed, transparent, itemised quotation for the agreed scope.
4. What is not included?
Why it matters: Kitchen units, flooring, decorating, landscaping, skips, parking suspensions, professional fees and VAT are common exclusions. Two quotes can look different only because of what they leave out. Read our house extension cost guide for the full list.
5. Is there a written contract?
Why it matters: The contract records the scope, price, programme, payment stages, how variations are priced and agreed, and what happens if something goes wrong.
Good answer: Yes, before any work starts.
Prohaus: Every project runs under a written and agreed contract.
6. How are payments structured?
Why it matters: Paying large sums in advance puts your money at risk.
Good answer: A modest deposit, if any, then staged payments linked to completed stages of work, with a retention or final payment after snagging.
7. What insurance do you hold?
Why it matters: Public liability insurance protects you and your neighbours if something is damaged or someone is hurt. Employer’s liability is a legal requirement for builders with employees.
Good answer: Certificates provided on request, with the cover and expiry dates visible.
8. Who carries out gas and electrical work, and what certificates will I receive?
Why it matters: By law, gas work must be done by a Gas Safe registered engineer. Notifiable electrical work must be certified under building regulations. You will need these certificates when you sell.
Good answer: The names of the registered businesses, which you can check on the Gas Safe Register and the relevant electrical scheme register, and confirmation of the certificates you will receive.
Prohaus: Gas and electrical work is carried out and certified by appropriately registered subcontractors, and the responsible trade is confirmed before regulated work starts.
9. Who handles planning, building control and party wall notices?
Why it matters: Missing approvals cause delays, enforcement and problems on sale.
Good answer: A clear statement of who submits each application, who appoints building control, and when party wall notices will be served. Read our planning permission guide and Party Wall Act guide.
Prohaus: We work closely with professional architects, designers and structural engineers through our planning and design service, and plan approvals and notices alongside the build programme.
10. Who will be on site, and who is my point of contact?
Why it matters: You need one person who answers your questions and coordinates trades.
Prohaus: We coordinate structural, carpentry, plumbing, electrical, tiling and decorating trades under one project plan.
11. How long will it take, and how do you handle delays?
Why it matters: A written programme lets you plan around the work. Weather, materials and hidden conditions can cause delays, and the contract should explain how they are handled.
Good answer: A written programme with key stages. As an example, a straightforward single-storey rear extension typically takes about 10 to 14 weeks on site.
12. What guarantee do you give?
Why it matters: A guarantee shows the builder will come back if something is not right.
Good answer: A written guarantee with clear terms. For new builds, ask about structural warranty providers.
Prohaus: Completed work has a 1-year guarantee, set out in writing.
02Red flags to watch for
- A quote with no breakdown, or a price far below the others with no explanation
- Requests for large cash payments upfront
- No address, no company details, or a phone number only
- Reluctance to put the scope or contract in writing
- Pressure to start immediately “before prices rise”
- Claims of gas or electrical registration that do not appear on the official register
- Advice to skip planning or building control
03How to check a builder yourself
| Check | Where |
|---|---|
| Company registration and directors | Companies House (find-and-update.company-information.service.gov.uk) |
| Gas engineers | Gas Safe Register |
| Electrical scheme registration | The competent person scheme register named by the electrician |
| Planning history at the address | Your council’s online planning register |
| Reviews | Google reviews and trade review sites, ideally with named past clients you can speak to |
Swipe the table sideways to see every column.
04Why local matters in Kingston and Surbiton
Housing across the Royal Borough of Kingston upon Thames ranges from Victorian and Edwardian homes near the town centre and Norbiton to 1930s semis towards Tolworth, Berrylands and Chessington. A local builder knows the borough’s conservation areas, the typical issues with each house type, and the practicalities of parking and deliveries on local streets. See builders in Kingston upon Thames and builders in Surbiton.
05Frequently asked questions
How many quotes should I get?
Two or three detailed quotes for the same scope is usually enough to compare price and approach. More than that often adds time without adding clarity.
Is the cheapest quote the best value?
Not necessarily. Compare what each quote includes and excludes, the quality of the specification, the programme and the contract terms.
Should I pay a deposit?
Some builders ask for a deposit to secure materials or a start date. Keep it modest, and make later payments against completed stages of work.
Do I need an architect as well as a builder?
For extensions and loft conversions, you will usually need drawings for planning and building regulations. Some builders work with architects and designers, which helps the design match the build.
What should I send a builder for a quote?
Your address, photos, a description of what you want, any drawings or planning documents, and your target start date.
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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.
Talk to Prohaus
We are a building company based in Kingston upon Thames. Send us your project details and we will arrange a conversation, a site visit and a written, itemised quotation.
