How do I find a reliable builder in London?

Start with the house, not a directory. Ask for work like yours — a rear that opened a thin kitchen, a loft that's in use — and visit one if you can. Get a written, itemised price after someone has been on site. Get a name who will run the job. Check any FMB claim on check a member. Ask to read the warranty. Never pay the full amount up front.

Should I hire a builder for labour only or design and build?

Labour-only if you already have drawings and you want to run the job — materials, trades, the programme. Design and build if you want one company from the brief to handover, so a wall on paper is a wall they have to build. Most standard London house jobs sit on that second side. The architect-versus-team question is covered in our do I need an architect guide.

What causes construction delays and how can I avoid them?

Unlocked design, materials ordered late, and nobody sequencing the site. Lock the layout before you start. Ask for a programme, and when the steels and windows are ordered. Keep one named person responsible for the day. Planning, if you need it, has to be clear before a start date means anything — that's the planning permission guide.

How do I know if a builder quote is fair?

Two or three quotes, same scope, itemised. Compare the exclusions, not only the total. The cheap one has often left the kitchen, the steels or the garden out — that's in common build mistakes. A from-£ on our costs page is the scale of a real job. It isn't a quotation.

What should a building contract include?

A fixed total once the design is locked, a scope that says what's in and what's out, a programme, payments tied to work that's done, a defects period, and the warranty in writing. Never pay the full amount up front. This isn't legal advice — contracts vary, and we won't invent a standard deposit.

Which construction company in London is best for extensions?

The one that's best for this house. Have they built your job — a modest rear, a wraparound, a loft — and can you walk a finished one? Did they visit? Is the quote the same scope as the others, fixed after design, with a name on site? Can you find the membership on FMB check a member? "Best in London" is a brochure line. Best for this kitchen is a visit, a piece of paper, and a badge you looked up yourself.

How to Choose a Builder in London

Two quotes on the kitchen table.

You're opening the thin kitchen onto the garden, or you're doing the unused loft.

One number is labour-only and looks cheap, until you'd be the one chasing trades.

The other firm priced from a photo and hasn't walked the house.

You're trying to tell who is safe to let in — not which website sounds more professional.

This is the chooser. It isn't a cost guide and it isn't a capabilities deck.

The cheapest-quote traps sit in 7 mistakes homeowners make. Architect versus design-and-build sits in do I need an architect. Build bands sit on costs.

Those pages aren't rewritten here.

This isn't legal advice. Contracts and deposits vary. We won't invent a standard London percentage.

Key Takeaways

1
Same scope on paper, itemised, so two quotes are actually the same job
2
Someone has visited the house. A number from a photo isn't a quote
3
A name who will run the site, not a generic inbox
4
A written price after the design is locked — not an estimate that moves
5
A badge you can look up yourself. Never the full sum up front

Short Answer

A rear extension is typically £60,000–£120,000+ on costs.

That's a real job, not a weekend quote.

The person you let through the door decides whether that number holds, and whether the kitchen you wanted is the kitchen you get.

You don't need a brochure. You need the same job written down, a site visit, a name, a contract you can read, and a membership you can check.

The wider cost picture is the extension cost guide. Don't treat either as a quotation.

The wrong builder isn't always the cheap one. Sometimes it's the one who never came to the house.

Design and Build vs Labour Only

This is the first fork.

Labour-only is right when you already have drawings, you want to buy the materials, and you want to run the programme yourself.

You become the project manager. Trades, deliveries, the gap when the steel doesn't match the drawing — that's yours.

Design and build is one company from the brief to handover. Design, planning, the build, one contract.

When something doesn't fit, there isn't an architect's office and a builder each pointing at the other.

Most London house jobs — a modest rear, a side return, a straightforward loft, a renovation — sit on the design-and-build side because the homeowner doesn't want that coordination.

The people drawing the opening are the people who will put the steels in.

If the live question is whether you need a registered architect at all, that's do I need an architect. Don't treat this page as that fork.

Trovix is a design-and-build firm. We use in-house designers.

We don't pretend every job needs an architect, and we don't pretend none do.

Red Flags

Walk away, or at least slow down, when any of these show up.

They won't visit the house. A quote from photos is a guess. London terraces hide the drains, the neighbour's foundations, the access.
The scope isn't itemised. The quote that isn't a quote leaves the kitchen out, or the steels, or the garden. That's the cheapest-quote mistake.
Cash only, or the full amount before anyone starts. Never pay the whole job up front. Payments should follow work that's actually done. We won't invent a typical deposit — contracts vary.
No name on site. If you can't get a straight answer about who turns up and who you call, you don't have a manager. You have a van.
A badge you can't find. Anyone can put a logo on a website. If they claim Federation of Master Builders membership, check the member yourself on FMB check a member.
They won't show finished work. Ask to visit a kitchen that's been lived in, not only a render. A finished loft. A rear that actually opened onto the garden.

What a Fixed Price Actually Means

Fixed means the total is written after the design is locked — survey, drawings, a visit to the house.

It isn't a number from a listing photo.

Until that design is agreed, you're looking at a starting band or an estimate. A from-£ on costs is a band.

A real quote names the house, the footprint and what's excluded.

Day-rate or "cost-plus" means the bill follows time and materials. That can be honest on a job that can't be specified yet.

On a standard rear or loft, it leaves the final number open.

We won't invent what it costs to get to a fixed price. Design, survey and the site visit are how you get there. There isn't a Trovix fee for that published on this page.

Checking the Badge

Anyone can call themselves a builder in the UK. There isn't a licence you must hold for domestic work on a house.

That's why independent membership exists.

The useful action is the check, not the logo. If they say they're in the Federation of Master Builders, use FMB check a member.

Ask for the name they trade under. Look them up on the FMB site, not on their own homepage.

Membership is a check on the builder. It isn't deposit insurance, and it isn't the warranty on your job. Those are separate pieces of paper.

Trovix is an FMB member. You can verify that on FMB or read the trust and standards page.

This article isn't that chrome, and we won't expand a membership number here.

Structural work should carry a written warranty you can actually read. Trovix already states a 10-year structural warranty on the site.

This page isn't that document, and it isn't the planning 10-year rule — different meaning, different clock.

How Jobs Slip

Most slips start before the skip.

The design isn't locked. Materials that take weeks — steels, windows, doors — haven't been ordered. Nobody is on site to sequence the trades. You change the island after the opening is cut.

Ask for a programme before anyone starts. Ask when the long-lead items get ordered.

Lock the layout before you dig — mid-build changes are the mistake that unpicks work that's already done.

If the job needs planning permission, get that route clear before you treat a start date as real. This page isn't the consent guide.

A Fair Quote

Get two or three quotes on the same scope. Itemised. Same kitchen, same steels, same garden, same exclusions.

The lowest number is often a different job. That's already written in common build mistakes. We won't invent a spread.

Compare the paper, then visit a finished house. A from-£ rear on costs tells you the scale.

It isn't a quotation, and this isn't a second cost table.

Questions Before You Sign

Keep it short. You don't need a sixteen-question ritual.

Is this a fixed total, or an estimate?
What's included, and what's excluded — kitchen, steels, garden, making good?
Who is the named person on site, and how do they update you?
Can I see a programme before work starts?
Can I read the warranty, not just hear that there is one?
How do you handle a change once the job has started?
What does each payment follow — which stage of actual work?
Can I visit a finished kitchen or a current site?
Can I see the insurance, and can I check the trade-body membership myself?
What happens if the job overruns the programme?

How they answer the first email is useful. Slow and vague now is slow and vague when the steels are late.

Worth knowing: Verify the badge on the trade body's own site. Never pay the whole job up front. Those two checks cost you an afternoon and they rule out a lot of the rest.

If You're Choosing Us, or Not

Trovix designs and builds. For a standard rear, a side return, a loft or a renovation, the in-house designers draw it and the same company builds it.

A written price comes after the design is locked, not from a photo.

We are one option on the design-and-build side of the fork. This page is how to choose, not a claim that we are the answer for every house.

If you've got two quotes on the table, or you haven't asked yet, book a consultation. We can look at the kitchen, the loft and whether labour-only or one team is the right job.

How that sequence runs sits on house extensions and loft conversions.

Common Questions