Do I need planning permission for a single-storey rear extension?
In most cases, no. Under Permitted Development rights in England, you can build a single-storey rear extension without planning permission if it meets certain rules:
Semi-detached or terraced houses: up to 3m deep. Detached houses: up to 4m deep. Height must not exceed 4m at the eaves or 3m within 2m of a boundary. Materials must match the existing house.
Larger extensions (up to 6m for semi/terraced, 8m for detached) may qualify under the Neighbour Consultation Scheme, which requires a 42-day notice period to neighbours.
Always check with your local planning authority before starting. Permitted Development rights can be removed by Article 4 directions in conservation areas or by conditions on your planning permission when the house was built.
Get a Lawful Development Certificate for peace of mind — it proves your build was lawful, which matters when you come to sell.
What's the difference between planning permission and building regulations?
Planning permission is about whether you're allowed to build something — its size, appearance, and impact on the area and your neighbours. It's controlled by your local council.
Building regulations are about how it's built — structural safety, fire escape, insulation, drainage, electrical installations, and other technical standards. Approved by a building control inspector.
You often need both, separately. Permitted Development means you may not need planning permission, but building regulations approval is almost always still required for any structural work, new electrics, or drainage changes.
Skipping building regulations sign-off creates serious problems when you sell — solicitors will ask for the completion certificate.
What is a party wall agreement and do I need one?
A party wall agreement (formally a Party Wall Award) is a legal document that protects you and your neighbour when building work affects a shared wall, boundary, or excavation near their property.
You likely need one if you're:
• Building on or at the boundary line
• Excavating within 3m of a neighbouring structure at the same depth, or within 6m on a deeper line
• Working on or cutting into a shared (party) wall
Serve written notice on all affected neighbours at least 2 months before work starts (1 month for excavations). If they consent in writing, you don't need a formal award. If they dissent or don't respond, both sides appoint surveyors and a Party Wall Award is issued.
Ignoring this is one of the most common and expensive mistakes homeowners make — neighbours can get an injunction to stop your build.
How do I find a trustworthy builder?
Get at least three written quotes and compare them on scope (what's included), not just price. A quote that's significantly cheaper usually means something has been left out or the builder plans to ask for extras later.
Ask for references from recent jobs of a similar type and actually call them. Ask: Did they finish on time? Did the price hold? Would you use them again?
Check Companies House — see how long the company has been trading, its directors, and whether it's been dissolved and re-formed (a pattern with rogue traders).
Visit a current job if possible. The site should be reasonably tidy, workers should be there, materials properly stored.
Look for membership of trade bodies like the Federation of Master Builders (FMB) or TrustMark — not a guarantee, but it adds a layer of accountability.
What should be in a builder's quote?
A proper written quote should include:
• Full scope of work — what's included and what's explicitly excluded
• A fixed price or, if day-rate, a maximum estimated total
• Payment schedule tied to completion milestones, not dates
• Start and estimated completion dates
• Who supplies materials — you or the builder
• Assumptions the price is based on (e.g. "assumes existing foundations are adequate")
• What happens if unforeseen issues arise and how variations are priced
An "estimate" is not a quote. It has no legal standing and the final price can be significantly different.
Should I always go with the cheapest quote?
No. The cheapest quote is often the riskiest. Common reasons a quote is low:
• The builder has left things out that they'll bill as extras later
• They're underqualified or underinsured
• They plan to use cheaper materials than specified
• They're desperate for work (for a reason)
The best approach is to get three comparable quotes, make sure they're for exactly the same scope, and choose based on the totality of evidence: references, communication quality, experience with this type of project, and price.
A quote 20–30% higher than the others often turns out cheaper in the end when you account for extras, delays and remedial work.
What insurance does my builder need?
At minimum:
Public Liability Insurance (at least £1–2m cover) — covers injury or property damage to third parties during the work. This is the most important one.
Employer's Liability Insurance — legally required if they employ staff or subcontractors. Minimum £5m cover.
It's also worth checking if they have Contractor's All Risks insurance, which covers damage to the works themselves (e.g. a wall collapses in a storm).
Ask for proof of insurance certificates before work starts and check the expiry date — policies lapse and builders don't always renew on time.
Note: your own home insurance may not cover building work unless you've notified your insurer. Check your policy and add a "works in progress" extension if needed.
How much should I pay a builder upfront?
A reasonable deposit is 10–15% of the total contract value. This covers initial material costs and mobilisation.
Be cautious of any builder requesting more than 20–25% before work begins. Never pay more than the value of completed work at any stage.
After the deposit, payments should be tied to completion of defined milestones — foundations poured, walls up, roof on, first fix complete, second fix complete, final snagging signed off. Never pay ahead of the work.
Should I pay my builder in cash?
No. Cash payments give you:
• No paper trail if there's a dispute
• No proof of what was paid and when
• No VAT receipts for materials
• No recourse if the builder disappears
If a builder requests cash specifically to avoid declaring it, you could be treated as complicit in tax evasion. The "discount" for paying cash is never worth the risk you're taking.
Always pay by bank transfer and keep a record of every payment with a note of what it was for — or use an app like Ted to track it properly.
What is a scope of work?
A scope of work is a detailed written document that defines exactly what your builder will do, what you'll supply yourself, what's excluded, and what the agreed quality standards are.
It removes ambiguity. "The kitchen extension" means very different things to you and your builder. A scope of work says: "Builder to supply and fit XYZ brand windows with a U-value of no more than X. Homeowner to supply tiles. Builder to lay tiles but not to supply adhesive."
It's the document that resolves disputes — because everything that was agreed is written down.
What is the CIS — Construction Industry Scheme?
CIS is a HMRC scheme governing how tax is deducted when contractors pay subcontractors in construction. Under CIS, contractors withhold 20% (or 30% for unregistered subcontractors) and pay it to HMRC on the subcontractor's behalf.
As a private homeowner paying a builder directly, CIS does not apply to you. It's a business-to-business rule.
However, if you're a landlord or running a business from the property, different rules may apply. Worth checking with an accountant.
On VAT: most new build residential work is zero-rated. Extensions and renovations to existing homes are standard-rated (20%). Some conversions qualify for 5% reduced rate. Ask your builder what VAT will be applied and make sure it's reflected in the quote.
Can I live in my house during a home extension?
Usually yes, but it depends on scale. Single-storey rear extensions are the most manageable — you'll lose kitchen or garden access at certain stages, but the rest of the house stays habitable.
You'll need to expect: significant dust (it gets everywhere despite sheeting), noise from 7am–5pm on working days, tradespeople walking through your home, and a compromised kitchen/bathroom for weeks at a time.
Consider moving out if: the work involves your roof structure, the project is a full-house renovation, asbestos removal is required, or you have young children or people with health conditions that make dust a serious issue.
→ Full guide: Can You Live in Your House During an Extension?
What is a snagging list and when do I do it?
A snagging list is a written record of every defect, unfinished item, and piece of work that doesn't meet the agreed standard — compiled before you make your final payment.
Do your snagging walk-through on a bright day. Bring the original specification or scope of work and check every room systematically. Common snags include: cracked or bubbled plaster, poorly fitted doors and windows, paint misses and drips, missing switches or sockets, grouting gaps, silicone not finished, external drainage not flowing correctly.
Your builder is contractually obliged to fix everything on the list before receiving final payment. Withholding final payment is your strongest negotiating tool — once you've paid, your leverage disappears.
My builder is asking for more money mid-project. What should I do?
Don't agree immediately. Say: "Send me a written breakdown of the additional costs and the reason they weren't in the original quote."
Not all extra cost requests are illegitimate. Genuine unforeseen structural problems (with photographic evidence), building control requirements you didn't anticipate, or changes you asked for are reasonable.
Red flags: "It's harder than I thought" (should have known before quoting), vague explanations with no documentation, threats to stop work, requests for cash.
For any significant amount, get a second opinion from an independent surveyor before agreeing to pay.
→ Full guide: Builder Asking for More Money — Red Flags & What To Do
How long does a house extension take?
A typical single-storey rear extension takes 12–20 weeks on site from groundworks to completion. Add 6–12 weeks for planning and design before you break ground.
Rough phases: foundations and drainage (2–3 weeks), walls and roof structure (3–4 weeks), waterproofing and windows (1–2 weeks), first fix (electrics, plumbing, insulation) (3–4 weeks), plastering and drying time (2–3 weeks), second fix and finishes (3–4 weeks).
Delays are extremely common. Builder availability, material lead times, planning delays, building control inspections, and poor weather all add time. Budget an extra 4–6 weeks mentally.
What do I do if my builder abandons the project?
Act quickly and systematically:
1. Secure the site. Lock gates, cover exposed structures with sheeting, turn off any utilities left active. A half-built structure is a liability and a theft risk.
2. Stop all payments immediately. Do not pay anything further until the situation is resolved.
3. Document everything. Photograph the current state of every area, dated. Gather all payment records, contracts, messages, and emails.
4. Write formally. Send a letter or email giving the builder 7 days to return to site or provide a written explanation. Keep a copy.
5. If no response, formally terminate. Send a written notice of contract termination.
6. Get quotes to complete the work. You'll need these as evidence of the additional cost caused by the abandonment.
7. Pursue recovery. Small claims court for amounts under £10,000, or seek legal advice for larger sums. Also report to Trading Standards.
→ Full guide: Builder Abandoned Your Project — Day-by-Day Action Plan
How do I dispute with a builder?
Start with a formal written letter setting out the issue clearly, what resolution you're seeking, and a reasonable deadline (14 days is standard). Keep it factual, not emotional.
If that fails, try mediation. Many trade bodies (FMB, TrustMark) offer free or low-cost mediation for members. It's faster and cheaper than court.
For amounts under £10,000 in England and Wales (£5,000 in Scotland, £5,000 in Northern Ireland), use the small claims court — it's designed for people without lawyers. Filing costs £35–£455 depending on the amount claimed.
For larger amounts, construction adjudication is faster than full litigation — legally binding decisions within 28 days.
Your strongest asset throughout: good documentation. Every payment record, every message, every photo of work at each stage. This is why tracking from the start matters so much.
What is Ted and how does it work?
Ted is a free app built for homeowners managing a building or renovation project. You create a project, then:
• Track payments — record every payment to your builder, attach receipts, and see your running total against budget
• Manage tasks — create a to-do list for your build, assign items to your builder
• Keep a daily journal — log progress with photos and notes every day
• Collaborate with your builder — invite them to the same project so you're both looking at the same information
The idea is to replace WhatsApp threads, spreadsheets, and paper receipts with one organised record of your entire project.
Ted is available free on iOS and Android.
Is Ted free to use?
Yes. Ted is completely free to download and use on iOS and Android. There are no subscriptions, no payment limits, and no hidden fees.
Track your build with Ted — it's free
One app for every payment, task and conversation with your builder. Available now on iOS and Android.
