Start with accreditations, not price
The instinct to compare quotes first and ask questions second is understandable — but it leads to predictable problems. The contractor who wins on price most often does so by cutting corners on insurance, skipping risk assessments, or using unqualified labour. Before you invite anyone onto your site, ask for proof of the following:
- Public Liability Insurance — minimum £2 million for residential work, £5 million or more for commercial or council projects.
- Employer's Liability Insurance — if they have any employees (including regular subcontractors), this is a legal requirement.
- CHAS or SafeContractor accreditation — these schemes assess health and safety competence and insurance as a package. An accredited contractor has been independently checked.
If a contractor cannot produce these documents promptly, walk away. This is not bureaucracy — it is what protects you if something goes wrong on site.
Verify that the team is employed, not just referred
Many contractors in London operate as referral intermediaries. They take your money, pass the work to whichever subbies are available, and take a margin. The result is a revolving cast of unfamiliar faces on your property, no accountability, and quality that varies from day to day.
Ask directly: are the people who will carry out the work employed by you, or are they subcontractors? There is nothing inherently wrong with specialist subcontracting — a joiner who brings in a specialist plasterer, for example — but the principal contractor should have a consistent, known team who they are accountable for.
Check references — actually check them
Ask for two or three references from projects similar in scale and type to yours. Call them. Ask specifically:
- Did the work finish on the agreed date, or close to it?
- Were there significant variations to the original price?
- Was the site kept tidy and the team respectful of the property?
- Would you use them again?
A contractor who cannot or will not provide references has told you something important.
Understand what the quote covers — and what it doesn't
A written quote is not just a number — it is a document that defines the scope of works. Read it carefully. Common omissions to look for:
- Scaffold costs (often quoted separately or excluded entirely)
- Waste removal and skip hire
- Making good after works — replastering, repainting disturbed surfaces
- Provisional sums for contingencies — what triggers them, and who authorises?
If the quote is vague — "refurbishment works as discussed" rather than a line-by-line breakdown — ask for clarification before you sign. Disputes about scope are the most common cause of contractor conflict.
Understand the payment structure
You should never pay the full sum upfront. A reasonable structure for a larger project is: a deposit (10–20%) to mobilise, stage payments tied to defined milestones, and a retention held until satisfactory completion. For smaller jobs, a deposit followed by payment on completion is normal.
Be cautious of any contractor who asks for a large cash payment before works begin and then disappears. It happens more often than it should.
The right fit matters as much as technical competence
You will be communicating with this person or team for weeks or months. Do they respond to messages? Do they explain things clearly when you ask? Do they treat your home or building with respect?
Technical competence is the baseline. But a contractor who is hard to reach, dismissive of your questions, or vague about what is happening is going to make the experience difficult regardless of the quality of the finished work.
The contractor you should be looking for is one who would rather lose the job than take on something they cannot deliver to the standard you need.