To choose a building contractor in Kent, check their trade-body membership, confirm their insurance, and insist on a written contract. Verify public liability and employer’s liability cover. Read independent reviews and speak to recent clients. Agree staged payments instead of a large deposit. These checks separate safe builders from risky ones.

Picking a builder is one of the biggest financial decisions you make at home. Get it right and your project runs smoothly. Get it wrong and you risk delays, defects, and lost money. This guide gives you a step-by-step checklist to vet any Kent builder.

You will learn what to check, what to ask, and what to avoid before you sign.

How do you check a building contractor is qualified?

Check a building contractor is qualified by confirming their company details, insurance, and trade-body membership. Look up the business on Companies House. Confirm any VAT number they quote. Search for them with the Federation of Master Builders (FMB), TrustATrader, or Checkatrade. These bodies vet members before listing, so membership is a fast credibility check.

Companies House is the UK’s official register of companies. Search the builder’s name there to confirm the business is registered and active. The incorporation date shows how long it has traded.

How to check a builder is legitimate:

1. Search the company name on Companies House to confirm it is registered and active.
2. Check how long the business has traded.
3. Confirm a VAT number if the builder charges VAT.
4. Look for membership of the FMB, TrustATrader, or Checkatrade.
5. Ask for a real business address and a landline.
6. Request proof of insurance and recent references.

The Federation of Master Builders (FMB) is the UK’s largest construction trade association. It was founded in 1941. Membership is one useful signal, though it is not the only one you should rely on.

Which trade body is best: FMB, TrustATrader, or Checkatrade?

The FMB, TrustATrader, and Checkatrade all vet their members, but to different depths. The FMB adds an independent inspection of real building work. The directory platforms do not. Checkatrade runs up to twelve background checks. TrustATrader vets traders and offers a guarantee. For structural work, FMB membership is the strongest single signal.

TrustATrader is an online directory of vetted UK traders. Checkatrade is an online directory that background-checks tradespeople and verifies reviews.

The FMB requires an independent inspection of a member’s real work before joining, according to the Federation of Master Builders in 2026. Directory platforms check business details, not the workmanship on your site.

Checkatrade members must pass up to twelve background checks, according to Checkatrade in 2026. Checkatrade also states it removed around 1,500 trades in the last year for failing its standards. You can read the FMB’s own guidance on finding and checking a builder at the Federation of Master Builders.

A builder listed on more than one of these platforms gives you the strongest reassurance.

What insurance should a building contractor have?

Every building contractor should hold public liability insurance and employer’s liability insurance. Public liability insurance covers injury or damage to your property and other people. Employer’s liability insurance is legally required when a builder employs staff. Ask to see current certificates before work starts. Check the cover level suits your project value.

Employer’s liability insurance is required by law for firms with staff, under the Employers’ Liability (Compulsory Insurance) Act 1969. A builder without it is either working alone or breaking the law.

Cover of 1 million to 5 million pounds is common for domestic building work. As of 2026, BDC Construction states it carries both public and employer’s liability insurance. Always ask for in-date certificates and match the cover to your project value.

What questions should you ask a builder before hiring?

Ask a builder for proof of insurance, recent references, a written quote, and a realistic timeline. Ask who runs the site each day. Ask how they price changes and handle delays. Ask about their payment schedule. Ask whether they provide a written contract and a guarantee. Clear answers signal a professional.

Ten questions to ask before you hire:

1. Can you show current public liability and employer’s liability certificates?
2. Can I visit two or three recent, similar projects?
3. Will you provide a fixed, written, itemised quote?
4. What are the start and finish dates?
5. Who supervises the site each day?
6. How do you price changes or extra work?
7. What happens if the job runs late?
8. What payment schedule do you use?
9. Will we sign a written contract?
10. What guarantee or warranty do you offer?

Vague or evasive answers are a warning sign. A professional builder answers each question plainly and puts the detail in writing.

Do you need a written contract, and which one?

Yes, always use a written contract for building work. For homeowners, two contracts suit direct hiring. The JCT Building Contract for a Home Owner/Occupier uses plain English. The FMB contract is free when you hire an FMB-registered builder. A contract records price, payments, timescales, insurance, and how you settle disputes.

The JCT (Joint Contracts Tribunal) produces standard building contracts used across the UK. Its Home Owner/Occupier contract is written for homeowners hiring a builder directly, without a consultant.

Even without a bespoke contract, the Consumer Rights Act 2015 requires services to be performed with reasonable care and skill. A signed contract still gives you far clearer footing if problems arise. You can view the homeowner contracts at the Joint Contracts Tribunal and read the law at legislation.gov.uk.

A good building contract records:

• The full scope of work and the fixed price.
• The payment schedule and any deposit.
• Start and completion dates.
• Insurance responsibilities.
• How variations and disputes are handled.

What is a structural warranty, and do you need one?

A structural warranty is insurance that covers defects in a building’s structure, usually for ten years. It pays out on proof that something has failed. You do not need to prove negligence. A workmanship guarantee is different, and comes from the builder directly. New builds usually need a warranty; extensions often benefit from one.

Warranty and guarantee are not the same thing. A workmanship guarantee is the builder’s own promise to fix faults. A structural warranty is backed by an insurer, so it still protects you if the builder stops trading.

Structural warranties usually run for ten years. Providers include NHBC, LABC Warranty, and Premier Guarantee. Lenders and future buyers often expect a warranty on a new build, so ask your builder what they offer in writing.

How should builder payments and deposits work?

Reputable builders take staged payments tied to completed work, not a large sum upfront. Expect a small deposit or interim payments as milestones are met. A final amount, called a retention, is held until snagging is done. Avoid paying in full in advance. Pay by bank transfer and record every payment.

Snagging is the process of fixing small faults near the end of a job. Holding a retention until snagging is finished protects you if final details are left undone.

How do you check a builder’s reviews and references?

Read a builder’s reviews on independent platforms, not only their own website. Weight repeat business and recent, dated jobs most heavily. Read full reviews that describe real projects, not one-line praise. Ask to speak to or visit two or three recent clients. Repeat customers are the clearest sign of quality building work.

Reviews on a builder’s own site are curated. Reviews on TrustATrader, Checkatrade, Google, and Houzz are harder to cherry-pick. Look for detail, dates, and clients who came back for a second job.

As a benchmark, a strong local record looks like this. As of 2026, BDC Construction holds 4.94 out of 5 from 79 TrustATrader reviews, built largely on referrals and repeat work. You can see completed projects on the recent projects across Kent page.

How many quotes should you get, and how do you compare them?

Get at least three written, itemised quotes so you can compare like for like. Check each quote for materials, labour, timescales, and exclusions. Treat the cheapest quote with caution, because it often means cut corners. A quote is a fixed price. An estimate is only a rough guide, so know which you have.

A good quote includes:

• An itemised breakdown of materials and labour.
• Clear start and completion dates.
• What is included and, just as important, what is excluded.
• Provisional sums for anything not yet fixed.

Costs vary widely by project, so compare scope, not just the headline figure. A cheap quote that leaves out key work is not a saving.

What are the red flags of a rogue builder?

Red flags of a rogue builder include pressure to decide fast and a large cash deposit demanded upfront. Be wary of no written contract, no proof of insurance, and no references. A quote far below the others is a warning. So is no fixed address or a builder who will not put things in writing.

Walk away if you see:

• A demand for a large deposit in cash.
• No written contract or quote.
• No verifiable insurance.
• High-pressure, “today only” tactics.
• No references or fixed address.
• A price far below every other quote.

One red flag is a reason to pause. Two or more is a reason to walk away.

Do you need planning permission or building regulations?

Most extensions and loft conversions need building regulations approval. Many also need planning permission, though some count as permitted development. A Party Wall agreement applies when work affects a shared wall. A good contractor explains which approvals you need and can suggest an architect. Responsibility for approvals sits with you, the homeowner.

Permitted development is work allowed without a full planning application, within set limits. The Party Wall etc. Act 1996 governs work on shared walls with a neighbour. You can check the rules at gov.uk.

The Construction (Design and Management) Regulations 2015 also apply to domestic building projects. A reliable builder guides you through approvals, but the legal duty to hold them stays with you.

How do you choose a builder in Kent?

For a Kent project, prioritise local references you can visit and recent work near you. Ask to see completed projects in Maidstone or your town. Check the builder knows local planning and conservation rules. Confirm they genuinely cover your area. Local knowledge and nearby proof reduce your risk on the project.

Local builders can show you real jobs a short drive away. They also understand Kent planning, conservation areas, and ground conditions. Confirm your builder covers your specific town before you shortlist them, using the areas we cover across Kent page, and review their extensions and loft conversions in Kent.

The takeaway

Choosing a builder comes down to proof. Check membership, insurance, contracts, reviews, and payment terms before you sign. Do that, and you protect both your money and your home.

Planning a project in Kent? BDC Construction is a Maidstone-based contractor that meets the checks in this guide. Get a free, no-obligation quote.

Not sure where to start? Begin with insurance and a written contract.