Part single, part two-storey extensions in Hythe (Hampshire)

Before you start in Hythe (Hampshire), here's what applies.

Postcode districts: SO45
County / area: Hampshire, 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: Woolston (2.5 miles), Southampton (3 miles), Portswood (4.7 miles)
Distance to Southampton: about 3 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 Hythe (Hampshire) we also work in Woolston, Southampton and Portswood, and across the rest of Hampshire. Postcode district in and near Hythe (Hampshire): SO45.

What it costs in Hythe (Hampshire)

For budgeting in Hythe (Hampshire), 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 Hythe (Hampshire)

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 Hythe (Hampshire) homes

Structure at the step

The first-floor wall above often sits over the new open-plan space, so it needs a steel beam or frame to carry it. Loads come down at different points than in a full two-storey design, and the engineer sizes the foundations to suit each part.

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

Understand the brief
At your home in Hythe (Hampshire) we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Hythe (Hampshire).
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Questions about part single, part two-storey extensions in Hythe (Hampshire)

Do I need planning permission for a part single, part two-storey extension in Hythe (Hampshire)?

Hythe (Hampshire) 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 much does a part single, part two-storey extension cost in Hythe (Hampshire)?

Our guide for South East England, which covers Hythe (Hampshire), 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 postcodes do you cover around Hythe (Hampshire)?

We cover Hythe (Hampshire) (SO45) and nearby places including Woolston, Southampton and Portswood, plus the rest of Hampshire. The first site visit is free.

Can the single-storey part be deeper than the two-storey part?

With planning permission, yes, and that is often the point of the design: the ground floor projects further into the garden while the first floor stays back from neighbours. Under permitted development, the depth limits for extensions of more than one storey can apply to the whole extension, so we confirm which route applies before drawings are finalised.

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

We also cover places near Hythe (Hampshire), including:

Other extensions in Hythe (Hampshire)

All two-storey extension services in Hythe (Hampshire) · Part single, part two-storey extensions across Hampshire

The quickest next step is a visit. We'll look at your house in Hythe (Hampshire) and give you an honest view of the options.