Replacing a front or back door: costs and choosing an installer

Replacing an external door needs Building Regulations sign-off and the right registered installer; here's how to commission it properly.

DR-01What this job actually involvesReplacing a front or back door means taking out the old door and frame and fitting a new one, usually in the same opening. It covers the door itself, the frame, hinges, locks, weatherproofing and making good the plaster or brickwork around the edges. If you're also changing the size of the opening, converting a window into a door, or fitting French or bifold doors where there wasn't a door before, that's a bigger job involving structural work. This guide covers both, but the structural version costs and takes longer.

DR-02Check what permission you needReplacing an external door is covered by Building Regulations, because it affects the home's insulation and, where there's glass, safety glazing. Most installers handle this themselves through a competent person scheme (FENSA or CERTASS) rather than you contacting Building Control directly. If your home is listed, you'll need listed building consent to change a door, even like-for-like. In a conservation area, a replacement door is usually fine unless an Article 4 direction applies, so check with the council. HomeGraft has a 'Know the rules' guide on Building Regulations and competent person schemes — check it before you book anyone.

RULES

KNOW THE RULES

Door replacement falls under Building Regulations (Part L for insulation, and safety glazing where there's glass). This must be certified either by a FENSA/CERTASS-registered installer or signed off by local authority Building Control. On a listed building you also need listed building consent; in a conservation area, check whether an Article 4 direction applies.

DR-03Decide if you need a structural engineer firstIf you're keeping the same size opening, you generally don't need a structural engineer — just a competent installer. If you're widening the opening, removing a window to create a doorway, or fitting large sliding or bifold doors, get a structural engineer in before you book a builder. They'll specify what support (a lintel, for example) the new opening needs. Get this step done first — a builder working without that specification is a common cause of problems later.

DR-04Find and check installersLook for installers registered with FENSA or CERTASS — this means they can self-certify the work as meeting Building Regulations, so you don't need to involve Building Control separately. Ask for their registration number and check it on the FENSA or CERTASS website. Get at least two, ideally three, quotes. Ask to see examples of similar doors they've fitted, and if possible speak to a recent customer.

DR-05What a good quote should containA proper quote names the exact door make, model and material, the glazing spec and U-value, and the security rating (look for PAS24 or TS007 on front doors). It should state whether removal and disposal of the old door is included, who makes good the plaster or brickwork afterwards, and the guarantee length on both the door and the fitting. It should also give a fixed price, a payment schedule, and a realistic start and finish date. Vague quotes with a single lump sum and no detail are a warning sign.

DR-06Realistic costs and timescalesFor a typical three-bedroom house outside London in 2026: a standard uPVC door supplied and fitted costs roughly £800 to £1,500; a composite door £1,200 to £2,200; a timber door £1,500 to £3,000 or more. Back doors, patio doors or French doors run from about £1,500 to £3,500. If the opening needs altering structurally, add £500 to £1,500 for engineering and extra labour, and £2,500 to £6,000 for a full French or bifold conversion. London and the South East usually cost 15–25% more. Bespoke sizes, solid timber, high-security specification, and matching requirements for listed buildings push a job to the top of the range. Expect 1–2 weeks for survey and quote, 2–6 weeks for manufacture (longer for timber), and 1 day to fit a straightforward swap, or 2–3 days if the opening is being altered.

DR-07Questions to ask, and red flagsAsk: Are you FENSA or CERTASS registered, and can I see the certificate number? What's the U-value, and does it meet current Building Regulations? What guarantee do you offer, and who do I contact if something goes wrong after you've left? Who's responsible if the opening needs altering once you start? Red flags include no registration number, cash-only insistence, no written breakdown, pressure to sign on the day, or no mention of a compliance certificate at the end.

DR-08What commonly goes wrongThe most common problems are a door ordered to the wrong size leaving gaps, poor sealing causing draughts and damp around the frame, and cheap hinges or locks that don't meet your home insurer's security requirements. On structural jobs, work sometimes starts without a proper engineer's specification, which can cause real safety and legal problems later. If a job is going wrong, stop and get a second opinion before paying any more.

DR-09After the work: certificates and sign-offOnce the door is fitted, you must receive a compliance certificate — either from FENSA or CERTASS if your installer is registered, or from local authority Building Control if they weren't. Keep this with your house paperwork permanently. Buyers' solicitors ask for it when you sell, and without it you may face delays or costs resolving it retrospectively.

RULES

KNOW THE RULES

Replacement external doors must meet Building Regulations. The certificate from FENSA, CERTASS, or Building Control is the proof. Missing certificates commonly cause problems at the point of selling a house.

DR-10If you live in Wales, Scotland or Northern IrelandIn Wales, the rules are very similar to England, and FENSA and CERTASS installers can self-certify there too. In Scotland, a straight replacement door usually doesn't need a building warrant, but making a new opening or widening one does, so check with your council's building standards team. In Northern Ireland, Building Regulations apply but are managed separately from England and Wales, so confirm with your local council's Building Control department rather than assuming FENSA cover applies.

RULES

KNOW THE RULES

In Scotland, new or widened openings need a building warrant before work starts. Northern Ireland has its own separate Building Regulations framework. Always confirm the correct route with the relevant local authority before work begins.

KNOW THE RULES

Before you start: Do I need Building Regulations approval to replace windows or doors? · What needs listed building consent?

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