Searching for a "builder near me" is easy. Working out which of those builders you can actually trust with your home, your money and six months of your life is the hard part. A house extension, loft conversion or full renovation is one of the largest purchases most people ever make outside of the house itself — and unlike a car or a kitchen, you are buying a promise of work that has not been carried out yet.
This guide explains exactly how to find a trusted builder in North London: what to look for, what to ask, what things genuinely cost in this part of the capital, and the warning signs that should make you walk away. It is written from the perspective of a Barnet-based contractor whose directors and site managers have over 25 years of combined industry experience across North London and Hertfordshire.
What to look for in a local builder
Every builder will tell you they do good work. The things worth checking are the ones that can be verified independently, before any money changes hands.
A real, registered company
Look the company up on Companies House. Check how long it has traded, that the registered address is real, and that the name on the quotation matches the name on the bank details. A builder who invoices from a different company name than the one they quote from is a risk you do not need to take.
Accreditations and insurance
- Public liability insurance — ask for the certificate, check the cover level and the expiry date.
- Employers' liability insurance if they employ staff on site.
- Trade accreditations relevant to the work (electrical, gas, structural).
- Building Control involvement — a competent builder expects inspections, they don't avoid them.
Local, verifiable references
Photos prove very little on their own. What matters is being able to speak to a homeowner whose project was a similar size and type to yours, ideally in a nearby postcode, and asking them the awkward questions: did the programme slip, how were variations priced, how was the site left at the end of each week, and would they use the same team again?
A written, itemised quotation
A trustworthy quotation shows what is included and — just as importantly — what is excluded. Structural steel, waste removal, scaffolding, Building Control fees, kitchen and bathroom supply, decoration and making good should all be either priced or clearly named as exclusions. A single figure on one page is not a quotation, it is a guess.
Questions to ask before hiring a builder
Ask every builder you shortlist the same set of questions and compare the answers side by side. The differences are usually more revealing than the prices.
- Who will be on site day to day, and who is my single point of contact?
- Is the price fixed, and how are variations priced and approved?
- What is the payment schedule, and is it tied to stages of completed work rather than dates?
- What is the programme, and what happens if it slips?
- Do you handle planning applications, Building Control and party wall notices, or do I?
- Which parts of the work are subcontracted, and are those trades certificated?
- What guarantee or warranty is provided after handover, and what does it actually cover?
- Can I visit a project you are working on right now?
Two answers should always give you pause: a request for a large deposit before any work starts, and pressure to sign quickly because the price is only valid this week. Genuine contractors have full diaries and do not need urgency to win work.
How much does a builder cost in North London?
Prices in North London sit above the national average because labour, access, parking, waste disposal and planning requirements all cost more here. The ranges below are indicative guide figures for the North London and Hertfordshire area at a standard-to-good specification. They exclude VAT and professional fees such as architects, structural engineers and planning charges, and they should never be treated as a quotation — the only accurate price comes after someone has walked round your property.
| Project type | Indicative range |
|---|---|
| Single storey rear extension | £60,000 – £120,000+ |
| Double storey extension | £90,000 – £180,000+ |
| Dormer loft conversion | £50,000 – £90,000+ |
| Hip-to-gable or mansard loft conversion | £65,000 – £120,000+ |
| Full house renovation | £100,000 – £300,000+ |
| Kitchen or bathroom refit | £20,000 – £60,000+ |
Where a quotation comes in far below every other price you have received, assume something has been left out rather than that you have found a bargain. Under-priced jobs are the ones that stall halfway through.
For a quick guide price on your own project, use our online cost estimator — it takes about a minute and gives you a realistic range to plan around.
Areas we cover in North London and Hertfordshire
We are based on High Street in Barnet and work throughout North London and southern Hertfordshire, including Barnet, Finchley, Whetstone, Totteridge, Mill Hill, Hendon, Edgware, Highgate, Hampstead, Muswell Hill, Friern Barnet, Winchmore Hill, Edmonton, Waltham Cross, Potters Bar, Borehamwood, Radlett, Brookmans Park, Hadley Wood and St Albans.
Each location has its own page with local planning guidance and recent projects nearby — see all the areas we cover.
Why local builders beat national firms for home projects
A local contractor knows how the London Borough of Barnet and neighbouring authorities treat rear dormers, how far you can extend under Permitted Development on a typical 1930s semi, which streets have restricted access for deliveries, and which parking permits you will need for a skip. That knowledge removes weeks of avoidable delay.
Local firms also carry a different kind of risk. Their next project usually comes from the street they last worked on, so the quality of the finish and the state they leave your home in matters to them commercially. National lead-generation platforms simply pass your enquiry to whoever paid for it, and the relationship ends there.
How The Construction Collective works
Our process is deliberately simple, and it is the same on every project regardless of size.
- Free consultation — we visit your home, listen to the brief and tell you honestly what is possible and what it is likely to cost.
- Design and planning — drawings, structural calculations, planning applications and Building Control, coordinated by us.
- Detailed quotation — an itemised fixed price with a clear programme, so you know what is included before you commit.
- Build — one site manager, one point of contact, weekly updates and a tidy, respectful site.
- Handover — final inspections, certification, snagging completed and a full set of documents for your records.
You can see completed work across North London in our project portfolio, or read more about the team behind the company.
Frequently asked questions
How do I find a good builder in North London?
Start with two or three local contractors who have completed projects like yours nearby. Check the company on Companies House, ask for insurance certificates and accreditations, speak to at least one recent client, and compare fully itemised written quotations rather than headline prices. Visiting a live site tells you more about a builder than any brochure.
What should I ask a builder before hiring them?
Ask who your day-to-day point of contact will be, whether the price is fixed and how variations are handled, how payments are tied to completed stages of work, what the programme is, who handles planning and Building Control, which trades are subcontracted, and what guarantee applies after handover.
How much does an extension cost in North London?
As an indicative guide, single storey rear extensions in North London typically range from £60,000 to £120,000+ and double storey extensions from £90,000 to £180,000+, excluding VAT and professional fees. The final figure depends on size, structural complexity, glazing and specification.
How long does a loft conversion take?
A dormer loft conversion typically takes 8–14 weeks on site once work begins, with larger hip-to-gable and mansard conversions towards the upper end. Design, planning and Building Control approvals beforehand usually add a further two to four months.
Do I need planning permission for an extension in London?
Many single storey rear extensions fall under Permitted Development rights and do not need a full planning application, but limits on depth, height and materials apply, and they are tighter on flats, conservation areas and listed buildings. We confirm the position at the free site visit and handle any application required.
Book a free site visit
If you are planning an extension, loft conversion or renovation anywhere in North London or Hertfordshire, we will visit your home, discuss your brief and give you honest advice with no obligation. Book your free site visit or call us on 020 8441 3144.