Part single, part two-storey extensions in Newhaven
Adding a part single, part two-storey extension in Newhaven gives you two new rooms stacked on one footprint. Here's how we'd approach it, what it typically costs and the rules that apply in England.
Useful details for planning a part single, part two-storey extension in Newhaven.
- Postcode districts
- BN9
- County / area
- East Sussex, England
- Price region
- South East England
- Guide price
- £79,000–£109,000 (£2,200–£3,030 per m²)
- Approval route
- It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission.
- Nearest towns
- Seaford (2.7 miles), Peacehaven (2.7 miles), Rottingdean (5.1 miles)
- Distance to Brighton
- about 8.8 miles
- First visit
- Free, no obligation
About a part single, part two-storey extension
A part single, part two-storey extension suits you if you want a generous ground floor but only need one extra room upstairs, or if a full two-storey design would affect a neighbour too much. You get design options that test where the two-storey part works best, the approvals your nation needs, structural design, building regulations approval and the build, carried out by vetted teams working under S&K.
Around Newhaven we also work in Seaford, Peacehaven and Rottingdean, and across the rest of East Sussex. Postcode district in and near Newhaven: BN9.
What it costs in Newhaven
For budgeting in Newhaven, allow around £79,000–£109,000 for a part single, part two-storey extension with a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total). That's based on £2,200–£3,030 per m² including VAT for South East England. Steelwork for wide openings is the item most likely to move the figure; we'll know once the engineer has designed it.
| Spec | Per m² | A 6 m × 4 m ground floor and a first floor over half of it (36 m² in total) |
|---|---|---|
| Essential | £2,020–£2,780 per m² | £73,000–£100,000 |
| Standard | £2,200–£3,030 per m² | £79,000–£109,000 |
| Premium | £2,640–£3,630 per m² | £95,000–£130,500 |
Planning and building regulations in Newhaven
In England, the extension can only be permitted development if it goes no more than 3 m beyond the original rear wall and stays at least 7 m from the rear boundary, with matching materials and roof pitch. We check the whole design against the rules, including the 50% garden coverage limit. If any part fails, or extends beyond a side wall on two floors, you need planning permission, costing £548 (or £575 for applications made from 8 December 2026).
Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.
Design points for Newhaven homes
Where to put the two-storey part
The two-storey section usually works best away from the closest neighbour, with the single-storey part on that boundary side. We test a few positions against neighbours' windows, the upstairs layout and the roof shape before choosing the one to take forward.
Light into the kitchen
The single-storey part is the place for roof lights or a lantern, which bring daylight deep into the plan. In England, glazing is normally limited to 25% of the new floor area plus any windows removed, unless calculations show the house still performs, so we plan the balance early.
How we'd run your project
Visit and first ideas
One of our team visits your house in Newhaven, checks the walls, roof and drains, and sketches out options with you.
Get it approved
Once you're happy with the design we submit it to the council for Newhaven and deal with any questions from the planning officer.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
Build it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.
Questions about part single, part two-storey extensions in Newhaven
Do I need planning permission for a part single, part two-storey extension in Newhaven?
Newhaven is in England, so England planning rules apply. It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.
How long does a part single, part two-storey extension take?
Allow 4 to 8 weeks for survey and design, then the approval period (councils should decide householder applications within 8 weeks of validation), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.
How much does a part single, part two-storey extension cost in Newhaven?
Our guide for South East England, which covers Newhaven, is £2,200–£3,030 per m² including VAT. A typical project with a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total) comes to about £79,000–£109,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Which side should the two-storey part go on?
Usually the side furthest from the nearest neighbour's windows, so the single-storey part sits nearest them and keeps their light. Other factors are where the stairs land upstairs, which room needs the extra space and where drains run. We sketch options at the design stage and explain which is most likely to be approved.
Can I add roof lights to the single-storey part?
Yes. Roof lights or a lantern over the single-storey part are one of the main reasons to choose this design, as they light the middle of a deep kitchen. In England they count towards the Part L glazing allowance, normally 25% of the new floor area plus windows removed, so we balance them with the rear doors.
Nearby
Nearby towns we cover for part single, part two-storey extensions:
Other extensions in Newhaven
- Rear
- Side
- Wraparound
- Over a garage
- First floor
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Newhaven · Part single, part two-storey extensions across East Sussex
Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.