How to Choose a Builder in London: What to Check Before You Sign

**1. Companies House registration** Check that the building company exists at Companies House (www.companieshouse.gov.uk — free). Look for: company number, registered address, date of incorporation, directors' names, filing history (accounts must be filed if trading). A company that has not filed accounts may be in financial difficulty. A company that was only formed a few weeks ago should be queried.

**2. Check for CCJs and adverse financial history** County Court Judgements (CCJs) can be checked via the Registry Trust (www.registry-trust.org.uk) for a small fee (£6 per search). A CCJ against a building company means they have been court-ordered to pay a debt and have not complied. Multiple CCJs are a serious warning sign.

**3. Verify Public Liability Insurance** Ask for the insurance certificate — the actual document, not just a statement that they have insurance. The minimum for a residential contractor in London is £2M public liability. Check: the policy is in date, the policy amount, and whether the contractor's activities match the insured operations. Do not accept a photocopy of an expired certificate.

**4. Check for Employer's Liability Insurance** If the builder employs staff (as opposed to using only subcontractors), they must hold Employer's Liability Insurance of at least £5M. This is a legal requirement. Ask for the certificate.

**5. Verify membership of a trade association** Memberships to check: Checkatrade and other verified contractor review platforms. However, be aware that some of these are membership organisations, not quality accreditors — check whether the contractor's membership is current and whether reviews are genuine.

**6. Request and check references — not testimonials** A testimonial on a website is marketing. A genuine reference means the contractor provides contact details for recent (within the last 2 years) former clients, and you call or visit them. Ask specific questions: did they start on time? Did they finish on time? Were there cost overruns? Would you use them again? Can you see the work?

**7. Visit a recent project** Ask to visit a recently completed project — ideally one similar in type and value to yours. A good contractor will be proud of their work and happy to arrange a visit with the client's consent. If a contractor cannot provide any recent project to visit, that itself is information.

**8. Check the VAT registration** If the contractor charges VAT, verify their VAT number at HMRC's VAT number checker (www.tax.service.gov.uk/check-vat-number). VAT fraud — charging 20% VAT and not paying it to HMRC — is a known issue in construction. A contractor claiming to be VAT-registered but unable to provide a VAT number is a warning sign.

**9. Ask about Building Control and structural engineering** A competent contractor will manage Building Regulations applications and Building Control inspections as part of their standard service. Ask: who will submit the Building Regulations application? Who coordinates the structural engineer? Who manages the Building Control inspections? 'You sort that out' is not an acceptable answer.

**10. Understand their contract** A professional contractor will use a written contract before starting. It should include: a clear scope of works, a start date and completion date (or programme), a payment schedule, a process for handling variations (changes), and a defects liability period. An oral agreement or a single-page letter is not adequate for a project over £10,000. Ask what contract they use — JCT Minor Works is the industry standard for smaller residential works.

**11. Check the payment schedule** A professional contractor will not ask for a large upfront payment. Reasonable payment structures: a deposit of 10–20% on contract signing (to cover mobilisation costs), then stage payments tied to measurable milestones (foundations complete, roof watertight, plastering complete, practical completion, defects sign-off). Any contractor asking for 50%+ upfront should be queried carefully.

**12. Check for a Building Regulations Completion Certificate from previous work** Ask a potential contractor: on your last extension project, can you show me the Building Regulations Completion Certificate? A contractor who routinely obtains Building Control Completion Certificates for their clients is one who is working within the correct legal framework. One who cannot produce this document — or who says 'the client handles that' — is one who may leave you with uncertified works.

Experience of London's construction market reveals consistent patterns of behaviour that precede problems:

**Pressure to decide immediately**: a professional contractor gives you time to consider. 'This price is only available today' or 'I have another client who wants this slot' are pressure sales tactics.

**Cash-only requests or avoidance of written quotes**: professional builders provide written, itemised quotes. Quotes that are vague, verbal, or that specifically exclude VAT 'if paid in cash' are warning signs.

**Starting before a contract is signed**: any contractor who wants to 'start tomorrow' before drawings are agreed, a contract is signed, or a Building Regulations application is submitted is one who is operating outside normal professional standards.

**Unable to name their structural engineer or architect**: a serious contractor has working relationships with structural engineers and architects. A contractor who 'figures it all out on site' without engineering input for structural work is dangerous.

**Significantly lower price than all other quotes**: if one quote is 30–50% below all others, it either means the scope is wrong (they have not understood what is needed) or the contractor will attempt to increase the price significantly mid-build ('price low to win, extras to profit'). Both are problems.

**No fixed address or only a mobile number**: a legitimate building company has a registered address and a non-mobile contact number (even if the day-to-day contact is a mobile). A contractor with only a mobile phone and no company registration is operating informally.

**Asking you to obtain the scaffolding or skip separately**: breaking the works into fragments that the client manages directly is a sign that the contractor is either disorganised or attempting to reduce their apparent price without reducing their actual cost to you.

When meeting a contractor to discuss your project, these questions reveal a great deal about their professionalism and approach:

• **About the project**:
• •Have you done a project similar to this recently?
• •Who is your structural engineer for this type of work?
• •How will you manage Building Control?
• •Will you be on site yourself or will you have a project manager? Who?
• •What is your typical crew size for a project like this?

• **About commercial terms**:
• •What contract do you use? Can I see a copy?
• •What is your payment schedule?
• •How do you handle variations (changes to the agreed scope)?
• •What is your defects liability period after completion?
• •Do you carry public liability insurance? Can I see the certificate?

• **About programme**:
• •When could you start?
• •What is your estimated programme?
• •What might cause the programme to extend, and what is your process if it does?

• **About references**:
• •Can you provide contact details for two or three recent clients with similar projects?
• •Can I visit a completed project?

The quality of the answers — not just the content — tells you a great deal. A contractor who answers confidently and specifically, who asks questions back, and who engages with the details of your project is more likely to be professional than one who deflects or gives vague answers.

Comparing quotes from multiple contractors is essential — but comparing them directly is harder than it looks.

**Scope gaps**: different contractors may not have included the same scope. One quote may include the structural engineer's fees; another may not. One may include all scaffolding; another may quote it separately. The lowest quote is rarely the cheapest project — compare the scope carefully.

**Specifications**: ensure all quotes are based on the same specification. If you have drawn the project and produced a Schedule of Works, ask all contractors to quote against the same document. This is the only way to compare like with like.

**Inclusions and exclusions**: read the exclusions on each quote carefully. Common exclusions that add cost later: structural engineer fees, party wall surveyor, Building Control fees, scaffolding, skip, tree removal, drainage connections, ground conditions risk.

**Contingency**: experienced contractors often suggest a contingency allowance of 10–15% above the fixed-price quote to cover unexpected site conditions (discovered rot, unexpected drainage routes, hidden structural issues). This is sound practice.

**Payment terms**: a quote that requires 40% upfront is not directly comparable to one that requires 10% upfront and stage payments — the former represents a higher financial risk to you.

**VAT**: check whether VAT is included in the quoted figure. A quote of £80,000 + VAT is £96,000. Ensure you are comparing inclusive or exclusive figures consistently.