Rear Extension Cost Guide
Planning a rear extension starts with the same question every homeowner asks: how much is this really going to cost? This page breaks down realistic budget ranges, approval fees, and the main variables that push pricing up or down.
Because your main domain already targets Nottingham, this page keeps the slug cleaner as /rear-extensions/cost/ instead of repeating the location in the URL. That reduces redundancy while keeping the topic focused within the site’s topical borders.
What does a rear extension usually cost?
For many households, the core cost sits across design, approvals, structure, glazing, and internal finishing. The biggest mistake is budgeting only for the shell and forgetting kitchens, steelwork, drainage, or control fees.
Straightforward single-storey builds
A typical rear extension often starts in this range, especially where the footprint is modest and the internal layout changes are controlled.
Useful square metre benchmark
UK extension pricing guides place many single-storey extensions in roughly this range before higher-end finishes and specialist glazing are added.
Structure-only comparisons
Some Nottingham-focused examples put a 3m x 6m rear extension shell around £27,000 before kitchen, upgraded finishes, and other extras are added.
Where your rear extension budget goes
Use this as a planning framework rather than a one-size-fits-all quote. The final figure depends on site conditions, specification, and whether you are changing the whole ground floor layout.
Core construction costs
- Groundworks and foundations.
- Brickwork, structure, roof, insulation, and plastering.
- Steel beams where walls are removed.
- Doors, glazing, rooflights, and external finishes.
- Electrical, plumbing, heating, and flooring.
Often overlooked extras
- Kitchen supply and installation.
- Drainage diversions and manhole changes.
- Structural engineer calculations.
- Building control charges and planning route costs.
- Contingency budget for unknowns in the existing house.
Planning and building control costs
Rear extension pricing is not just build cost. Nottingham approvals and control fees can materially affect your budget, especially if you compare planning permission, prior approval, and full plans routes.
| Item | Typical amount | Notes |
|---|---|---|
| Householder planning application | £548 | Current Nottingham planning guidance cites a householder fee of £548 as of April 2026. |
| Larger home extension prior approval | £120 | Useful where the extension goes beyond standard PD depth but still sits within the larger home extension route. |
| Lawful Development Certificate | £129 | Often used as formal proof that planning permission is not required under permitted development. |
| Building control, over 10m² up to 40m² | £323 plan fee + £439 inspection fee | Nottingham City Council’s domestic charges table lists these full plans charges for extensions in that size band [page:2]. |
| Building notice, over 10m² up to 40m² | £802 | The same Nottingham charge table lists £802 for a building notice application in this extension size band [page:2]. |
How planning rules affect cost
Your approval route changes both cost and project speed. That is why the first technical check should happen before finalising the budget.
Standard rear extension limits
Planning Portal says many extensions can proceed without full planning permission where permitted development limits are met. For single-storey rear extensions, the standard limit is up to 4 metres on detached houses and 3 metres on other houses, subject to the wider conditions and restrictions [page:1].
Larger home extension route
Where not on Article 2(3) designated land and subject to prior approval, those rear limits can increase to 8 metres on detached houses and 6 metres on other houses. That route can reduce full planning cost, but it still requires the local authority to be informed and the conditions to be met [page:1].
Important: Planning Portal notes that Article 4 directions, planning conditions, flats, maisonettes, converted houses, and designated land can remove or restrict permitted development rights. That is why rear extension pricing should always be tied to the actual property, not just a generic online estimate [page:1].
Main factors that increase or reduce rear extension cost
Two extensions of the same size can land at very different budgets. Specification and complexity matter as much as the footprint.
Layout changes
Removing multiple load-bearing walls, relocating soil pipes, or reworking the entire ground floor will cost more than a simple add-on space.
Glazing and roof design
Large sliding doors, roof lanterns, flush thresholds, and higher-spec aluminium systems quickly push the budget upward.
Kitchen specification
A rear kitchen extension budget can shift dramatically based on cabinetry, worktops, appliances, electrics, and bespoke joinery.
Ground conditions
Poor ground, drainage changes, nearby trees, and access constraints may require deeper foundations or more labour.
Planning route
Permitted development, prior approval, or full planning each carry different fees, timings, and drawing requirements [page:1].
Finish level
Basic decorating versus premium flooring, glazing, lighting, and joinery creates a large difference in final cost even if the shell is the same.
How to plan your budget without nasty surprises
A more reliable budget comes from sequencing the work properly. That reduces retrieval cost for both users and search engines because the page answers intent directly: not just “how much,” but “what makes it change.”
Check the planning route
Start with permitted development, prior approval, or planning permission. This sets the right drawing and application path [page:1].
Estimate the structural brief
Decide the footprint, wall removals, glazing style, and whether the kitchen or utility layout changes.
Include fees early
Add planning, certificate, engineering, and building control costs instead of treating them as afterthoughts [page:2].
Add a contingency
A 10% buffer is often sensible to cover hidden issues and scope shifts during the build.
Related extension pages
This page supports the main service page and should internally link both upward and sideways to strengthen the cluster.
Rear Extensions
Main parent service page for design, planning, process, and build details.
Rear Extension Planning Permission
Dedicated explainer for PD limits, prior approval, and when full permission is required.
Kitchen Rear Extensions
A narrower subtopic for kitchen layouts, glazing, and family-space design.
Rear extension cost FAQs
How much does a rear extension cost?
Many straightforward single-storey rear extensions begin around £40,000 to £60,000, while larger, more design-led, or higher-spec schemes can cost more.
Is the kitchen included in that figure?
Not always. Some shell-cost examples exclude kitchen supply, appliances, upgraded flooring, decorating, and specialist glazing, so always check exactly what the quote includes.
Can I avoid planning permission?
Sometimes. Many rear extensions can fall under permitted development, but that depends on the property type, depth, height, previous extensions, and whether local restrictions apply [page:1].
What are the local building control fees?
For domestic extensions over 10m² up to 40m², Nottingham City Council lists a £323 plan fee and £439 inspection fee for full plans, or £802 for a building notice application [page:2].
Need a realistic rear extension budget?
We can price your project around the actual layout, approval route, and finish level you want, rather than giving you a vague online range.