Double storey extensions

Double storey rear extensions in Nottingham

A double storey rear extension builds out from the back of the house on both floors, usually with a kitchen, dining or family room below and a bedroom or bathroom above. It suits homes with enough garden depth where both floors feel short of space.

Building at the rear brings its own questions: how close you are to the back boundary, what the neighbours’ windows see, and how the new upstairs rooms join the existing landing. We work these out at the survey, then handle the design, approvals and build.

  • Ground and first floor designed as one scheme
  • Rear boundary distance and neighbours’ light checked early
  • Landing and stair changes planned before drawings are submitted
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What it is

Two floors of new space at the back of the house

A double storey rear extension projects from the rear wall and rises to the full height of the first floor. The ground floor usually opens up the back of the house into a kitchen-diner or family room with doors to the garden. Upstairs, the same footprint can hold a double bedroom, a main bedroom with an en-suite, two smaller bedrooms or a family bathroom.

Because both floors share the foundations and roof, the rear is often the most efficient place to add a lot of space at once. It does mean building closer to the back boundary and to neighbouring gardens at first-floor level, which is why the rear-specific checks below matter more than they do for a single storey rear extension.

If you are still weighing up rear, side and over-garage options, start with our overview of double storey extensions. If a bedroom is the main goal, our bedroom extension page compares this route with building over a garage or converting the loft.

Suits homes where

  • There is reasonable depth between the rear wall and the back boundary
  • The kitchen and the bedrooms both feel cramped
  • The landing can be extended to reach new rooms
  • Materials can be brought in via side access or through the house

Typical time on site

Around 12 to 18 weeks on site for most projects, as an indicative guide. Design, planning and Building Regulations come before this.

Rear-specific checks

What shapes a two-storey rear design

These are the points that most often decide the depth, roof shape and window positions of a rear extension on two floors.

Distance to the rear boundary

For permitted development, no part of an extension of more than one storey can be within 7m of the boundary opposite the rear wall, and it can go no more than 3m beyond the original rear wall. On shorter gardens a planning application is usually needed instead.

Neighbours’ daylight

Councils often assess two-storey rear extensions against a 45-degree line taken from the nearest ground or first floor window of the neighbouring house. A shallower first floor, a set-back from the boundary or a hipped roof can help a design pass.

Overlooking and privacy

New bedroom windows look over gardens at first-floor height. Under permitted development, upper-floor side windows must be obscure-glazed and non-opening unless the opening part is more than 1.7m above the floor, and councils often look at how rear windows face neighbouring homes.

Staircase and landing

The new rooms have to be reached from the existing landing. That can mean taking part of a back bedroom or bathroom for a corridor, moving the bathroom, or turning the top of the stairs. We plan this before the drawings are fixed.

Roof and existing windows

A pitched or hipped roof matched to the house is common, and the pitch should match as far as practicable for permitted development. The extension often covers an existing first-floor rear window, so that room may need a new window.

Drains and ground

Drains and manholes often run across the back of a house. Building over a public sewer usually needs the water company’s agreement, and trees or poor ground can mean deeper foundations for the two-storey load.

Approvals

Planning, Building Regulations and party walls

Planning permission

A two-storey rear extension may fall under permitted development, depending on the property and any restrictions. It must meet all the Class A conditions, including the 3m depth and 7m boundary rules, height and eaves limits, matching materials and obscure-glazed side windows. It is not permitted development in a conservation area or on other Article 2(3) land, and Article 4 directions, listed status or conditions from an earlier permission can also remove the option. The full list is on our double storey extensions page.

A common design uses a deeper single storey kitchen with a shorter first floor above, which keeps the upstairs bulk away from neighbours. Whether that fits permitted development or needs an application depends on the exact dimensions, so your property needs to be checked. A Lawful Development Certificate confirms the position in writing.

Building Regulations

Building Regulations approval is separate from planning and always needed. For a rear extension the main items are the foundations, the steel beams over the opened-up rear wall, insulation and glazing area, drainage, and fire safety for the new first-floor rooms, including escape windows.

Party Wall etc. Act 1996

On semi-detached and terraced houses the new foundations are usually close to a neighbour’s wall or on the boundary, so Party Wall notices are often needed before work starts.

Useful to know before the survey

  • Roughly how far it is from the rear wall to the back fence
  • Where the neighbours’ nearest rear windows are
  • Any manhole covers in the garden
  • Whether you are in a conservation area
  • Which first-floor room could give up space for a corridor

What we coordinate

Drawings, the planning route, structural calculations, Building Regulations approval and Party Wall notices, so each approval is in place before the relevant work starts.

How it runs

From survey to handover

1

Free survey

We measure up, check the rear boundary, drains and access, and talk through what you want on each floor.

2

Design and drawings

Plans for both floors, the landing link, elevations and the roof, tested against neighbours’ light and privacy.

3

Planning route

A Lawful Development Certificate or a householder planning application, depending on the design.

4

Itemised quotation

A written, itemised quotation and an agreed start date once the design and approvals are settled.

5

Groundwork and shell

Foundations, walls, first floor and roof go up while the house stays closed off.

6

Break-through and fit out

The rear wall is opened on steels, the landing is linked, then services, plastering and finishing.

7

Handover

Final building control inspection, a walk round with you and the completion paperwork.

Guide costs

Double storey rear extension prices

Indicative 2026 guide ranges, not a quotation. You get a written, itemised quotation after a free survey.

Size and typeApprox floor areaGuide price (2026)
Small double storey rear (single width)Up to 20 sqm total£60,000 to £80,000
Medium double storey rear20 to 35 sqm total£80,000 to £110,000
Large full width double storey rear35 to 50 sqm total£110,000 to £150,000
Premium finish or complex siteVaries£150,000+

On rear projects the price moves most with the width of the opening and the steelwork it needs, foundation depth, drain diversions, the glazing to the garden, the kitchen specification and how materials reach the back of the house. Changes to the existing landing and making good upstairs are part of the cost too.

See the work

See the work before you decide

Photos and past customers tell you more than a sales page can.

Browse the project gallery

Completed extensions grouped by type, including two-storey work.

How we check reviews

We only publish feedback once it has been matched to a real job.

Ask for a reference

At your survey, ask to speak to a past customer who had similar work done.

FAQs

Double storey rear extension questions

Not always, but many do. A two-storey rear extension may fall under permitted development if it goes no more than 3m beyond the original rear wall, stays at least 7m from the boundary opposite, and meets the other Class A conditions. Conservation areas, Article 4 directions, listed buildings and removed permitted development rights all rule that route out. Building Regulations approval is needed either way.

Under permitted development, no part of an extension of more than one storey can be within 7m of the boundary opposite the rear wall. If your garden is shorter than that once the extension is added, you would need a planning application, where the council looks at the effect on neighbours rather than a fixed distance.

It can, which is why councils often assess rear extensions using a 45-degree line from the neighbour’s nearest window. A two-storey extension is more likely to cross that line than a single storey one. Reducing the first-floor depth, moving it away from the boundary or using a hipped roof are common ways to reduce the impact.

The new first floor often covers it. That room can get a new window in another wall, borrow light through the new space, or be reworked as the corridor or bathroom that leads into the extension. We settle this at the design stage so the existing rooms still work.

Through the existing landing. Depending on the layout, that can mean extending the landing, taking part of a back bedroom or bathroom for a corridor, or changing the top of the stairs. Headroom and a safe escape route both have to work for Building Regulations.

As an indicative 2026 guide, our ranges run from £60,000 to £80,000 for a small single-width project up to £110,000 to £150,000 for a large full-width one, and £150,000 or more for premium finishes or complex sites. You get a written, itemised quotation after a free survey.

Most take around 12 to 18 weeks on site as an indicative guide. Design, any planning application or Lawful Development Certificate, Building Regulations approval and Party Wall notices come first, and none of these stages runs to a fixed date.

Most families do. The shell goes up while the back of the house stays closed. Expect a spell without a working kitchen when the rear wall is opened up, and dust upstairs when the landing is broken through. We tell you in advance which rooms are affected.

Check what fits behind your house

A free site survey measures the rear boundary distance, looks at your neighbours’ windows and drains, and shows whether a two-storey rear extension is realistic. You then get a written, itemised quotation.