How to Choose a Renovation Contractor in London

The renovation market in London is large and unregulated. Almost anyone can call themselves a contractor. The gap between the best firms and the worst is enormous — and the consequences of choosing badly, on a project of any significant scale, can be severe.

This guide gives you a practical framework for evaluating contractors before you commit.

Why this matters more in London than elsewhere

London's renovation market has specific characteristics that make contractor selection more complex than in most other places:

• —Volume and pace — there is more renovation work in central London than most contractors can handle. This means firms can be selective; but it also means some less reputable operators rely on a constant stream of new customers rather than repeat business.
• —Listed buildings and conservation areas — the majority of prime London postcodes are conservation areas. Work on listed buildings requires specialist knowledge and planning experience that most generalist contractors do not have.
• —Multi-trade complexity — a full renovation in London typically involves structural engineers, architects, planning consultants, party wall surveyors, and multiple specialist trades. Coordinating these requires project management capability that many small firms lack.
• —Scale of investment — renovation projects at the top of the London market routinely run into hundreds of thousands of pounds. The stakes are high.

Step 1: Establish whether they are set up for your type of work

Before asking for a price, ask whether the contractor regularly works on projects of your type and scale.

A firm that primarily does kitchen refits is not the right choice for a whole-house renovation. A generalist builder who has never worked on a listed building is not the right choice for a Grade II townhouse. Asking direct questions about their recent project history takes five minutes and tells you a great deal.

Specifically ask:

• —What was your largest project in the past 12 months, by value?
• —Do you have experience with listed buildings / conservation areas?
• —How do you manage multiple trades on site simultaneously?
• —Who will be on site every day, and who do I call if there is a problem?

Step 2: Check their credentials and insurances

Any serious contractor should be able to provide, without hesitation:

• —Public liability insurance — minimum £2m for residential work, £5m for larger projects
• —Employers' liability insurance — mandatory if they have employees
• —Professional indemnity — relevant for design-and-build contractors
• —Accreditation — Federation of Master Builders (FMB), NICEIC (electrical), Gas Safe (gas works) are the most relevant for residential renovation
• —Companies House registration — verify the company exists, check filing history, look at any County Court Judgements (CCJs) via a simple credit check

A contractor who cannot provide insurance certificates on request, or who suggests working off the books to avoid VAT, should be declined immediately. This is not only illegal; it leaves you entirely unprotected if something goes wrong.

Step 3: Evaluate the quote carefully

A low quote is not good news. In London's renovation market, it almost always means one of the following:

• —The contractor has underpriced the job and will seek to recover margin through variations
• —They have missed items from the scope that will be added later
• —They are using lower-quality materials or subcontractors than specified
• —They are less experienced and therefore less able to price accurately

A good quote should be itemised — line by line, trade by trade. It should include allowances for contingency (typically 10–15% on a complex project), and should be clear about what is and is not included.

When comparing quotes, compare like for like. If one is significantly lower than others, ask the contractor to explain the difference specifically. Sometimes it reveals a genuine saving; more often it reveals an omission.

Step 4: Check references — properly

Most contractors will provide references. The question is whether you use them.

Call the references. Ask specific questions:

• —Was the project delivered on time and on budget?
• —How were variations and unexpected costs handled?
• —Was the site kept clean and secure?
• —How did the contractor communicate during the project?
• —Would you use them again for a project of similar scale?

If a contractor cannot provide references from projects of similar type and scale to yours, treat this as a significant red flag.

Step 5: Assess the contract

Any work above a few thousand pounds should be governed by a formal contract. For significant renovation projects, a JCT Minor Works or Intermediate Contract is standard.

Key terms to check:

• —Payment schedule — tied to defined stages of completion, not to dates or contractor cash flow demands. Never pay more than 25–30% upfront.
• —Retention — typically 5% held back until practical completion and again until the end of the defects liability period (usually 12 months)
• —Variation procedure — how are changes to scope instructed and priced? This is where disputes most commonly arise.
• —Programme — a project programme should be attached, with key milestones
• —Defects liability — what is the contractor obliged to fix, and for how long after completion?

If a contractor is unwilling to sign a formal contract, do not proceed.

A note on price

Premium renovation in London costs more than in most other markets. This is a function of London labour rates, material lead times, planning complexity, access constraints, and the standard expected by clients at the top of the market.

Trying to achieve premium results on below-market budgets leads to below-market outcomes, rework, and — often — the cost of bringing in a second contractor to fix what the first one did.

ASAAN works at the top end of the London market. We are not the cheapest option, and we do not try to be. If you would like to discuss your project, we are happy to meet at your property and give you an honest view of what is involved. Contact us or view our portfolio to see our recent work.