Question 1

Do I need planning permission for a kitchen extension?

Accepted Answer

Most single-storey rear kitchen extensions don't need planning permission if they fall within permitted development (PD) rights. Key PD limits: extends no more than 3m (semi/terraced) or 4m (detached) beyond the rear wall, is no taller than 4m, and covers no more than half the original garden. If you're unsure, apply for a Lawful Development Certificate (around £100) to get formal confirmation — useful when you come to sell.

Question 2

What is permitted development for a house extension?

Accepted Answer

Permitted development (PD) is a set of rights that allow certain building works without a formal planning application. For rear extensions, you can build up to 3m beyond the original rear wall on a semi-detached or terraced house, or 4m on a detached house. The extension must be single-storey, no taller than 4m at its ridge, and the total footprint of all extensions and outbuildings must cover less than half the original curtilage. These rights don't apply to flats, listed buildings, or homes in Conservation Areas.

Question 3

How close to my boundary can I build an extension?

Accepted Answer

Under permitted development, an extension must be at least 2m from any boundary if its eaves are more than 3m high. There's no minimum distance for lower eaves, but practically most builders leave at least 150–300mm from a boundary for waterproofing and maintenance access. If your extension is within 3m of a neighbouring property's foundations (or 6m for deeper foundations), you'll also need to serve a party wall notice.

Question 4

What is a Lawful Development Certificate (LDC)?

Accepted Answer

A Lawful Development Certificate is a formal confirmation from your local planning authority that your proposed extension is lawful under permitted development rights. It costs around £100 and takes 6–8 weeks. It's not compulsory, but it gives you a paper trail that's useful when selling your home, and prevents disputes with neighbours or planners later. If there's any doubt about whether your extension qualifies as PD, an LDC is worth getting.

Question 5

How much does a kitchen extension cost in the UK?

Accepted Answer

A typical single-storey rear kitchen extension costs between £30,000 and £80,000 depending on size, specification, location, and whether you include a new kitchen. In the South East and London, prices are higher. A basic 15–20m² extension with a mid-range kitchen could be £40,000–£60,000. Full cost breakdowns vary widely — get at least three quotes before committing to a budget.

Question 6

How much does a kitchen extension cost per square metre?

Accepted Answer

Build costs (structure only, excluding kitchen) typically run £1,500–£2,500 per m² depending on specification and region. A high-spec extension with glazed roof lantern, underfloor heating, and bi-fold doors sits at the upper end. When budgeting, add the kitchen itself (£5,000–£30,000+), plus architect fees (£1,500–£3,000), structural engineer (£500–£1,500), and building control fees (£800–£1,500). Many people underestimate the non-build costs.

Question 7

How much contingency should I budget for a kitchen extension?

Accepted Answer

Budget at least 15–20% contingency on top of your builder's quote. Common unexpected costs include: deeper foundations due to tree roots or clay, asbestos found in older properties, utility diversions, variations in your specification once the build starts, and delays that extend temporary accommodation costs. On a £50,000 build, that means keeping £7,500–£10,000 unallocated. If you don't use it, great — if you need it, you'll be glad it's there.

Question 8

What factors affect the cost of a kitchen extension the most?

Accepted Answer

The biggest cost drivers are: size (larger footprint = more material and labour), specification (glazed roofs, underfloor heating, and bi-folds push costs up sharply), location (London and South East builders charge significantly more), site access and ground conditions (clay, tree roots, or poor access add cost), and the kitchen itself. The kitchen fitout can easily cost more than the build. Keep your budget realistic by separating the build cost from the kitchen budget.

Question 9

How long does a kitchen extension take?

Accepted Answer

From the moment you decide to go ahead to the day you cook in your new kitchen: expect 6–9 months if things go to plan. That breaks down as: planning and design (2–4 months), construction on site (10–16 weeks), and kitchen fitting and finishing (2–4 weeks). The planning phase is where most people underestimate time — waiting for drawings, building control, and party wall responses all adds up before a single brick is laid.

Question 10

What order do you build a kitchen extension?

Accepted Answer

The broad sequence is: 1) Groundwork and foundations, 2) Walls and blockwork, 3) Steelwork and lintels, 4) Roof structure and covering, 5) Windows and external doors, 6) First fix (pipes, cables, underfloor heating), 7) Insulation and plasterboard, 8) Plastering, 9) Second fix (sockets, switches, radiators, sanitaryware), 10) Kitchen installation, 11) Flooring, tiling and decoration. Building control inspections happen at key points — foundations, steelwork, and a final completion inspection.

Question 11

What is first fix and second fix?

Accepted Answer

First fix is all the work that happens inside walls and floors before plastering — running cables, water pipes, soil pipes, and underfloor heating pipes. Second fix is everything that happens after plastering — fitting sockets, switches, radiators, sanitaryware, kitchen units, and appliances. The two-phase approach exists because you can't plaster over hidden pipework and wiring until it's been inspected and tested. Understanding the distinction helps you sequence kitchen design decisions correctly: your kitchen layout must be finalised before first fix.

Question 12

What building control inspections are needed for an extension?

Accepted Answer

For a typical kitchen extension, building control will inspect at: 1) Foundation excavations before concrete is poured, 2) Damp-proof course level, 3) Oversite and drainage, 4) Structural steelwork before it's covered, 5) Insulation before boarding out, 6) Final completion inspection. You must notify building control before work starts and request each inspection — don't cover work without sign-off or you may be asked to expose it for inspection later.

Question 13

Should I project manage my own kitchen extension?

Accepted Answer

Project managing your own extension can save 10–15% in project manager fees, but it requires real time commitment — expect to spend several hours per week chasing quotes, coordinating trades, managing deliveries, and attending building control inspections. The main risks are: underestimating the coordination burden, missing dependencies between trades, and not knowing what you don't know. If you use a single main contractor, the PM burden is lower. If you're directly managing separate trades (groundworker, bricklayer, roofer), it's a substantial part-time job.

Question 14

What does project managing a kitchen extension actually involve?

Accepted Answer

Day-to-day PM tasks include: getting and comparing quotes, scheduling trades so they arrive in the right order, managing payment schedules, ordering materials and ensuring deliveries arrive on time, attending building control inspections, dealing with snagging, and making design decisions quickly to avoid delays. Good project management is mostly about sequencing — knowing that kitchen layout decisions must happen before first fix electrics, or that party wall agreements take months to resolve. This site maps those dependencies so you don't learn them the hard way.

Question 15

Is it cheaper to project manage your own extension?

Accepted Answer

Potentially yes — a professional project manager typically charges 10–15% of the build cost, so on a £60,000 build that's £6,000–£9,000. But DIY project management has hidden costs: your time (expect 5–10 hours/week for the build period), potential mistakes from lack of experience, and the stress of managing contractors directly. If you use a main contractor, they effectively PM the subcontractors for you — the question is whether you manage them, or pay someone else to.

Question 16

How do I find a reliable builder for my extension?

Accepted Answer

Best approaches: ask neighbours and local Facebook groups for personal recommendations (far more reliable than directory sites), check the Federation of Master Builders (FMB) membership (vetted builders with a dispute resolution scheme), and get at least three quotes from local contractors. Always ask for references from recent similar jobs and follow them up. Be wary of builders who want large upfront deposits, can start immediately (good builders are usually booked weeks ahead), or can't provide proof of public liability insurance.

Question 17

How much should I pay a builder upfront for an extension?

Accepted Answer

A deposit of 10% of the quoted value is reasonable for most reputable builders. Be cautious of anyone asking for more than 20% upfront. Payment should then be tied to completion milestones — for example: 25% on completion of groundwork, 25% on completion of structure, 25% on completion of first fix, and the final 10–15% held until after a snagging inspection. Always get a written contract that specifies the payment schedule before any money changes hands.

Question 18

What questions should I ask a builder before hiring them?

Accepted Answer

Key questions: Can they provide references from similar jobs completed in the last 12 months? Are they a member of the FMB or similar trade body? Can they provide proof of public liability insurance (minimum £2m)? How far in advance are they booked? Will they use subcontractors, and if so, who manages them? What does their payment schedule look like? Will they provide a written contract? What's included and excluded in the quote? How do they handle variations? Who is the named person responsible on site day-to-day?

Question 19

What is building control and do I need it for an extension?

Accepted Answer

Building control (also called building regulations approval) is a statutory inspection service that checks your extension meets minimum standards for structure, fire safety, insulation, drainage, and ventilation. Unlike planning permission, you almost always need building control approval for a kitchen extension — it applies even when planning permission isn't required. You notify building control before starting and they inspect at key stages. At completion, they issue a completion certificate — important for future sale and re-mortgaging.

Question 20

What is a party wall agreement and do I need one?

Accepted Answer

A party wall agreement (more precisely, a Party Wall Award) is required when your building work affects a shared wall or is within a certain distance of a neighbour's foundations. For extensions, the relevant trigger distances are: within 3 metres of a neighbouring property's foundations, or 6 metres if your new foundations are deeper. You serve a party wall notice, and your neighbour has 14 days to consent or dissent. If they dissent, a surveyor process begins — typically costing £700–£1,500 per neighbour and taking 6–8 weeks. Start this process early; it's the most common cause of delays.

Question 21

What is an SDS drill and do I need one for a kitchen extension?

Accepted Answer

An SDS (Slotted Drive System) drill is a rotary hammer drill designed for drilling into masonry — brick, block, and concrete. Unlike a standard combi drill, it uses a hammering action that drives the bit through hard materials far more effectively. For a kitchen extension, you'll need an SDS drill if you're drilling into external walls, fixing lintels, installing wall plugs into masonry, or hanging anything heavy. Hiring one is often better than buying if you only have one project. SDS bits (which fit the drill) are different from standard masonry bits — make sure you buy the right type.

Question 22

What is a utility meter relocation and why does it matter?

Accepted Answer

If your gas or electricity meter is located on the rear wall where your extension will be built, it must be moved before construction starts. This is handled by your Distribution Network Operator (DNO), not your energy supplier — a common source of confusion. Lead times are 6–8 weeks minimum, and the cost varies (typically £500–£1,500 depending on the complexity). This is one of the most common early delays on kitchen extension projects because homeowners discover the need too late. If your meter is on any wall the extension might affect, contact your DNO as soon as you have drawings.

Kitchen Extension FAQs

Planning Permission

Costs and Budgeting

Build Stages and Timeline

Project Managing Your Extension

Finding and Managing Builders

Understanding the Basics

Want the full step-by-step guide?