How to Choose a Reliable Builder in London

I've been building across London for over twenty years, and I'll let you in on something: not all builders are created equal. I've followed on from enough botched jobs to know the difference between a professional outfit and a chancer with a transit van. Here's how to tell them apart before you hand over a deposit.

The Non-Negotiables: What Every Builder Must Have

Before you even discuss your project, check these credentials. A legitimate builder will have them ready to show you without hesitation.

Public Liability Insurance

Minimum £2 million cover—and for London, I'd recommend £5 million. This protects you if something goes wrong: a wall collapses, someone gets injured, a fire starts. Without it, you're personally liable. Ask for the certificate and check the dates. Policies lapse, and some builders "forget" to renew.

Employer's Liability Insurance

If they have any employees (not just subcontractors), this is a legal requirement—£10 million minimum. Again, ask to see it.

A Registered Business Address

Search Companies House. Are they a limited company? How long have they been trading? A builder who's been operating for five years and has accounts on file is a safer bet than one who set up six months ago. Not foolproof, but it's a data point.

💡 Builder's Truth: "I'm just a sole trader" isn't necessarily a red flag—plenty of good builders operate this way. But they should still have insurance, a fixed business address, and proper invoicing. Cash-only, no paperwork? Walk away.

Red Flags: What Should Make You Nervous

After two decades, I can spot a problem builder from the first conversation. Here's what to watch for:

Red Flag	Why It's a Problem
Asks for more than 10-15% deposit upfront	They may be using your money to finish someone else's job—or might disappear entirely
Can start tomorrow	Good builders in London are typically booked 4-12 weeks ahead. Immediate availability suggests they can't get work
Quote significantly lower than others	Either they've underestimated the job (you'll pay later in "extras") or they're cutting corners on materials and labour
Reluctant to put things in writing	Verbal agreements are worthless when things go wrong. No contract = no protection
No fixed address or landline	Mobile-only and PO Box address makes them very difficult to pursue if they vanish
Pressures you to decide quickly	"This price is only good until Friday" is a sales tactic. Professionals don't work that way
Won't provide references	If they can't point to happy clients, there probably aren't any

Actually Visit a Previous Site

This is the single most valuable thing you can do, and barely anyone bothers. Ask your prospective builder for the addresses of two or three previous clients. Then actually visit.

I'm not talking about the polished photos on their website—I mean knock on the door, speak to the homeowner, and see the work with your own eyes. Ask them: Did the builder turn up when they said? How did they handle problems? Would they use them again?

💡 Builder's Truth: I actively encourage potential clients to speak to my previous customers. If a builder makes excuses about why you can't—"data protection" or "they're on holiday"—that tells you everything.

The Contract: What It Must Include

Don't sign anything until you've read it properly. A proper building contract should include:

Detailed scope of works: Exactly what's included and what isn't
Fixed price or method of calculating variations: How will extras be priced?
Payment schedule: Tied to specific milestones, not dates
Start and completion dates: With provisions for delays
Defects liability period: Typically 6-12 months after completion
Insurance details: Confirmation of valid cover
Dispute resolution process: What happens if things go wrong

For larger projects (£30,000+), consider using a standard JCT Minor Works or JCT Homeowner contract. These are industry-standard and protect both parties fairly.

Payment Stages: How to Protect Yourself

Never pay for work that hasn't been done. A sensible payment structure for a typical London extension or refurbishment might look like:

10-15% deposit on signing contract (to cover initial materials)
25% on completion of structural work
25% on first fix (plumbing, electrics, plastering)
25% on second fix (bathrooms, kitchen fitted)
10% on practical completion and snagging

Keep that final 5-10% until snagging is complete. It's remarkable how quickly outstanding issues get fixed when there's money waiting.

What About Trade Body Memberships?

Memberships of the Federation of Master Builders, TrustMark, or Checkatrade can be useful but aren't guarantees. They indicate a builder has met certain standards and agreed to a code of practice—but due diligence is still essential.

One advantage: these bodies usually offer mediation services if disputes arise. That alone can be worth something.

London-Specific Considerations

Building in London has particular challenges that an experienced local builder will understand:

CPZ and parking suspensions: Skip permits and parking suspensions add £50-100 per day. Your builder should factor this into their quote
Party wall agreements: Essential for terraces and semis—budget £700-1,500 per neighbour
Restrictive covenants: Some London properties have historic restrictions on building works
Conservation areas: Extra planning considerations in many boroughs
Access constraints: Narrow streets and limited parking affect logistics and costs

Thinking About a Project?

If you're weighing up builders and want a second opinion on what you're being quoted, feel free to get in touch. I'm always happy to have an honest chat—even if you don't end up using us.

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