10 min read
If you have searched ‘how long does a house extension take’ and landed on a national guide quoting six months, you have probably already noticed it does not quite add up. Those figures often assume London pricing, a clean planning run, and a contractor ready to start on Monday. In the North East — Newcastle, Gateshead, Northumberland, County Durham — the honest answer is a little different. Not worse. Just more specific. This post works through every stage, gives you real 2026 numbers, and flags the things that quietly extend timelines when no one has warned you they would.
The short answer
In short: a straightforward single-storey rear extension in the North East typically takes 8–12 months from first design brief to final handover. The on-site build alone is usually 14–24 weeks. If your scheme sits within permitted development rules and design moves quickly, you can get closer to 4–6 months total. If you need full planning permission and your contractor has a sensible lead time, 8–12 months is the more realistic target to plan around. Budget-wise, current 2026 guide rates for a single-storey rear extension in this region run at roughly £1,650–£2,200 per m²; a two-storey extension typically comes in at £1,400–£1,950 per m². Smaller extensions commonly start around £22,000–£45,000, though specification and site conditions move that figure considerably.
Why most guides mislead you on timelines
National ‘how long does a house extension take’ articles compress the timeline because they are usually written around the build phase only. They quote 12 weeks on site and leave you to assume everything else is quick. It is not. Design takes time done properly. Approvals have statutory clocks that nobody can rush. Good contractors have lead times. When you add those stages back in, the realistic total is longer — and that is fine, because knowing it up front lets you plan properly rather than being surprised halfway through.
There is also a persistent southern skew in UK home improvement content. Labour rates, planning authority workloads, and material logistics differ meaningfully between London and the North East. This post focuses on what the timeline actually looks like here.
The full timeline, stage by stage
Below is how the stages stack up for a typical North East extension project. Stages overlap where they can — building regulations work, for example, can run alongside the tail end of planning — but the sequence below is the logical order of dependency.
| Stage | Typical duration | Notes |
|---|---|---|
| Planning and feasibility | 1–3 weeks | Define brief, agree budget range, commission measured survey, decide planning route |
| Design and drawings | 4–8 weeks | Measured survey, concept design, planning drawings, construction drawings |
| Planning approval (if needed) | 10–14 weeks real-world | Statutory target is 8 weeks; real timelines at most North East LPAs currently run 10–14 weeks |
| Building regulations / technical approval | 3–6 weeks | Can run alongside design coordination and late planning stage |
| Contractor mobilisation | 2–6 weeks | Often underestimated; good contractors have lead times |
| Groundworks and foundations | 2–4 weeks | Varies with soil conditions, drainage routes, and site access |
| Main build | 8–16 weeks | Simple single-storey extension; longer for larger or more complex schemes |
| Second fix, snagging, handover | 1–2 weeks | Testing, decoration sign-off, building control final inspection |
Stage 1 — Planning and feasibility (1–3 weeks)
This is the stage most homeowners do not count. Before a line is drawn, someone needs to visit the site, understand what you want, sense-check what is structurally and spatially possible, and advise on the planning route. If pre-application advice from the local planning authority is warranted — useful on trickier sites or conservation area plots — allow extra time on top. Done well, this stage saves weeks later by avoiding design work that heads in the wrong direction.
Stage 2 — Design and drawings (4–8 weeks)
A measured survey of the existing house comes first — this is not something to skip or rush. From that, the designer produces concept options, you refine, and the project moves to planning drawings and then construction drawings. Four weeks is achievable for a simple scheme with a decisive client. Eight weeks is more realistic when there are structural questions to resolve or the brief evolves (which it usually does, at least a little).
Stage 3 — Approvals
Permitted development
If your scheme stays within permitted development limits — single-storey rear extension, within the volume and height rules, not in a designated area — you can avoid a full planning application entirely. You may still want a lawful development certificate for peace of mind when you sell, which takes around 8 weeks. But the hard planning clock is removed, and that alone can cut your total timeline by 2–3 months.
Full householder planning application
Where full planning is required, the statutory decision target in England is 8 weeks. In practice, most North East local planning authorities are currently running at 10–14 weeks for straightforward householder applications. The application fee in 2026 is £462 — that covers the council fee only and is separate from what your designer or consultant charges to prepare and submit the application.
Building regulations
Separate from planning, building regulations approval covers structural, thermal, fire, and drainage compliance. This typically takes 3–6 weeks and can run in parallel with the tail end of the planning process and the contractor procurement stage, so it does not always add time to the critical path.
Stage 4 — Groundworks and foundations (2–4 weeks)
Once on site, foundations are the first physical work. The range here is genuinely wide. A clean rear-garden plot with straightforward soil and no drainage conflicts at the shallow end. A sloped site, made ground, tree root protection zones, or drainage diversions at the longer end. Your structural engineer’s specification drives this stage, and it is worth understanding their assumptions before you set expectations with your contractor.
Stage 5 — Main build (8–16 weeks)
For a simple single-storey rear extension, 8–12 weeks on site is a reasonable expectation. More complex schemes — larger footprints, two storeys, structural alterations to the existing house, high-specification finishes — push toward 16 weeks or beyond. The main build stage is where delays from weather, material lead times, and subcontractor sequencing tend to show up, so building a small buffer into your planning is sensible rather than pessimistic.
Stage 6 — Second fix, snagging, and handover (1–2 weeks)
The final stage covers second-fix electrical and plumbing, tiling and decoration sign-off, building control final inspection, and snagging. One to two weeks is realistic for a tidy project. Rushing this stage is where small problems get buried rather than fixed — a false economy.
Scenarios: how the total timeline compares
| Scenario | Total timeline (realistic) |
|---|---|
| Permitted development, simple scheme, contractor ready | 4–6 months |
| Full planning, straightforward householder application | 6–9 months |
| Typical homeowner project including design changes, approvals, contractor lead time | 8–12 months |
| Complex scheme, two-storey, structural works to existing house | 12–18 months |
What actually pushes the timeline out
Most timeline overruns come from a predictable set of causes. Knowing them in advance lets you manage them rather than be caught by them.
- Brief changes during design. Entirely normal, but each significant change resets some design work. The more you can front-load your thinking before the designer starts drawing, the smoother this stage runs.
- Planning conditions. Approvals often come with conditions — materials to be agreed, drainage details to be submitted. Each condition needs to be formally discharged before you can build, and that takes time with the LPA.
- Contractor lead times. Good builders in the North East are busy. Assuming you can start on site the week after approval is optimistic. Six to eight weeks between appointment and mobilisation is common; sometimes more.
- Structural surprises. Opening up an existing house for a new opening or steelwork connection regularly reveals something unexpected — undersized joists, non-standard foundations, services in inconvenient places. A contingency in both budget and programme is not pessimism; it is experience.
- Drainage and groundwork complexity. Soil surveys are not always done before tendering. If the ground conditions differ from assumptions, the programme adjusts.
Costs alongside the timeline: what to expect in the North East in 2026
Timeline and budget are linked — higher-specification finishes take longer to procure and install, and larger schemes simply take longer to build. The figures below are current 2026 guide rates for North East England. They are not quotes.
| Extension type | North East guide rate (2026) | Example size | Indicative range |
|---|---|---|---|
| Single-storey rear extension — standard spec | £1,650–£2,200/m² | 20m² | £33,000–£44,000 |
| Single-storey rear extension — premium spec | £2,200–£2,600/m² | 20m² | £44,000–£52,000 |
| Two-storey extension — standard spec | £1,400–£1,950/m² | 30m² | £42,000–£58,500 |
| Smaller extension or garden room — entry level | From approx. £22,000 | 12–15m² | £22,000–£35,000 |
North East pricing sits among the lower regional bands in the UK. That is genuine — labour costs here are structurally lower than in London and the South East — but ‘lower’ does not mean cheap, and the cost difference narrows when high-specification materials and finishes are involved, since those are priced nationally.
Hidden costs most quotes do not include
The build cost is not the total project cost. These items are regularly omitted from early ballpark figures and catch homeowners out when they arrive.
- Measured survey: typically £400–£800 for a domestic property depending on size and complexity.
- Architect or designer fees: commonly 8–12% of construction cost for a full service from concept to completion.
- Structural engineer: typically £600–£1,500 for a straightforward extension; more if there is significant existing structure to assess.
- Planning application fee: £462 in 2026 (council fee only).
- Building regulations application: typically £400–£900 for a domestic extension depending on local authority and scheme type.
- Party wall surveyor fees: required where you are building on or near a boundary shared with a neighbour. Costs vary but £800–£1,500 per surveyor is common.
- Contingency: 10–15% on top of the build cost is the professional standard recommendation. On a £40,000 build that is £4,000–£6,000 held in reserve — not spent, but available.
- Temporary accommodation or storage: if the extension involves significant works to the rear of a lived-in house, there may be periods where part of the ground floor is unusable.
Why the North East is different — and what that means in practice
National guides are calibrated around national averages. The North East has some genuine differences worth understanding.
Labour rates are lower here than in London and the South East, and that is a real saving reflected in the build cost. A project that might cost £2,500–£3,000/m² in London is genuinely more affordable to build in Newcastle or County Durham.
Planning authority caseloads vary. Newcastle City Council, Northumberland County Council, Gateshead Council, and Durham County Council each have their own workloads and processing cultures. Some are faster than others at different times. Your designer will know the current state of play for your specific LPA.
Material logistics are largely neutral for standard materials — timber, block, concrete are all priced and available. For highly specified materials (large-format glazing, bespoke steel, specific stone) lead times can add weeks, and that is true anywhere.
Ground conditions vary more than people expect across this region. Former mining areas in County Durham and parts of Northumberland, riverside sites in Newcastle and Gateshead, and coastal plots all carry specific ground risk. A proper ground investigation at feasibility stage is money well spent on anything other than the most straightforward site.
A worked example
To make this concrete: a homeowner in a 1930s semi in the Team Valley area of Gateshead wants a single-storey rear kitchen extension, roughly 20m², mid-range specification, with bi-fold doors and a roof lantern. The rear neighbour is close enough that a party wall notice is required.
| Item | Estimated cost |
|---|---|
| Measured survey | £550 |
| Architect / design fees (concept to completion) | £4,200 |
| Structural engineer | £900 |
| Planning application fee | £462 |
| Building regulations | £600 |
| Party wall surveyor | £1,100 |
| Build cost (20m² at £1,900/m²) | £38,000 |
| Contingency (12%) | £4,560 |
| Realistic total | £50,372 |
Timeline for this project: planning application needed (no permitted development on this plot due to a previous extension). Realistic total: 9–11 months from first brief to moving back into the kitchen. Build on site: approximately 14–16 weeks.
How to compare quotes properly
Getting two or three quotes is sensible. Getting them on a like-for-like basis is harder than it sounds. Here is how to do it properly.
- Fix the specification before you ask for prices. Quotes based on a vague brief are not comparable. If one contractor prices bi-fold doors and another prices French doors, the difference in quote is not a reflection of their rates — it is a reflection of different assumptions.
- Check what is and is not included. Ask each contractor to confirm: does their price include groundworks? Drainage? Structural steelwork? Plasterboard and skim, or just structure? Decoration? Each of these is a legitimate variable and should be explicit.
- Ask how they handle variations. Changes mid-build happen. How a contractor prices and communicates variations tells you a lot about how the project will feel when something unexpected comes up.
- Check their programme. A quote with no programme is harder to manage. Ask for a simple week-by-week programme for the build stage so you understand the sequencing and can plan your own life around key milestones.
- Ask about subcontractors. Most main contractors subcontract electrics, plumbing, and sometimes groundworks. Who are they? How long have they worked together? This matters for quality and for the timeline.
- Do not select on price alone. The lowest quote on an extension is not automatically the best value. A contractor who is clear, communicative, and experienced in residential extensions will cost you less stress — and often less money — over the course of a project than one who is purely cheap.
A note on what is coming next
If you are getting to the stage of thinking seriously about a project, one question that tends to follow the timeline question is: how does the whole thing actually get managed? Who coordinates the designer, the structural engineer, the contractor, the building inspector? We are writing a detailed post on exactly that — How a Renovation Project Is Managed From First Survey to Final Handover — which will walk through the coordination and communication structure of a well-run residential project. Worth reading before you commit to a procurement approach.
Talk to Hollinside when you are ready
Hollinside works across Newcastle, Gateshead, Northumberland, and County Durham on premium residential extensions and renovations. We take on a small number of projects at a time — by design, not by accident — because that is the only way to give each one the attention it needs. There is no sales process here. If you want to talk through your project, what it might involve, and whether we are a sensible fit, that conversation is available whenever you are ready. No pressure, no obligation.
Last updated: June 2025. All figures are guidance only and do not constitute a quote. Costs and timelines vary with site conditions, specification, planning authority, and market conditions at the time of tender.