Gainsborough annexe extensions, designed and built
Our design and build teams take on annexe extensions in Gainsborough, from the first measured survey through planning and building control to the finished room.
- Guide price in GainsboroughFrom £52,000 inc VAT
- PlanningUsually a householder application
- Build time16–24 weeks on site
- Postcode districtsDN21
Planning rules that apply in Gainsborough
In England an annexe that stays part of the household and connects to the house is assessed as an extension, but its size usually takes it beyond permitted development, so a householder application describing the ancillary use is the normal route.
Homes in conservation areas, national parks, National Landscapes (formerly AONBs), the Broads and World Heritage Sites have tighter rules, so we always check the property's status and planning history before design starts.
Building over or within 3 m of a public sewer needs the water company's consent, usually through a build-over agreement, before the foundations go in.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Applications are decided by the local planning authority (your district, borough or unitary council).
How much does an annexe extension cost in Gainsborough?
Prices below are for Gainsborough, using the East Midlands factor of ×0.95. They are guide ranges including VAT for the build only, not a quote.
Typical rates in Gainsborough: £1,900 to £3,610 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| Studio annexe 25 m² | £52,000 – £65,500 | £57,000 – £71,500 | £71,000 – £90,500 |
| One-bedroom annexe 35 m² | £66,500 – £83,500 | £79,500 – £100,000 | £99,500 – £126,500 |
| Larger annexe 45 m² | £85,500 – £107,000 | £102,500 – £128,500 | £128,000 – £162,500 |
Try the guide-price tool to see a range for your own size and finish.
What is included
- Design for accessibility: level thresholds, wider doors, walk-in shower
- Fire separation and alarms to building regulations
- Kitchenette, shower room and bedroom finish
- Separate or shared heating and hot water
- Planning application describing ancillary use
Accessibility is cheaper to design in than to retrofit. Level access, a 900 mm door width, a level-access shower and space to turn a wheelchair can all be planned into the footprint for little extra cost.
Extensions in and around Gainsborough
Site visits are available across Gainsborough (DN21). We also work in nearby Scunthorpe (14 miles), Lincoln (14 miles), Grimsby (31 miles), Cleethorpes (33 miles).
Homes across the East Midlands often have usable side land or a driveway beside the house, which opens up side and wraparound options.
Our process, step by step
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
We visit your Gainsborough home, measure up, talk through what you want and check the planning position.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Your questions about an annexe extension in Gainsborough
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Gainsborough, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Will my neighbours in Gainsborough be involved?
If a planning application or prior approval is needed, the council notifies neighbours. If the work is on or near a shared boundary, party wall notices may also be needed.
Do I need building regulations approval in Gainsborough?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Can the annexe have its own front door?
Yes, many do, but it should still connect to the main house to stay clearly part of it.
Does an annexe extension need planning permission?
Usually yes, because of its size and the way it will be used. Councils check that it stays ancillary to the main house, so the application must describe the use clearly.
Book a free site visit in Gainsborough
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.