Single Storey vs Two Storey Extension: Which Is Right for Your Home?

If you are thinking about extending your home in Nottinghamshire, one of the first decisions you will face is whether to build a single storey or a two storey extension. It is a choice that will affect your budget, your planning prospects, your garden and the way your home works for years to come.

At MO Architects, we help homeowners across Nottingham, West Bridgford, Southwell, Newark, Bingham and the wider East Midlands work through exactly this kind of decision. There is no universal right answer — but there is almost always a right answer for your property, your family and your site. This guide explains how to think it through.

What is the difference between a single storey and two storey extension?

A single storey extension adds floor space at ground level only - typically to the rear or side of a property. Common examples include kitchen extensions, open-plan living spaces, garden rooms, utility rooms and orangeries.

A two storey extension adds space on both the ground floor and the first floor. This might mean a new kitchen below with a bedroom or bathroom above, or additional living space on both levels. Some two storey extensions include a loft-level element, effectively creating a three-storey addition - though these require careful planning consideration.

Both types of extension can transform how a home functions. The question is which one delivers the best outcome for your specific circumstances.

Planning permission: how does each compare?

Planning permission is often the first thing homeowners ask about - and rightly so. Getting this wrong at the start leads to delays, redesigns and unnecessary stress.

Single storey extensions have the best chance of falling within permitted development rights, which means you may not need a full planning application at all. Under current rules, a single storey rear extension can be built under permitted development if it does not exceed four metres in depth for a detached house, or three metres for a semi-detached or terraced property. Larger single storey extensions — up to eight metres for detached and six metres for semi-detached — may be possible under the Neighbour Consultation Scheme, though neighbour objections can affect the outcome.

There are important exceptions. If your home is in a conservation area - including large parts of Southwell, the Laxton Conservation Area, or conservation villages across Newark and Sherwood — permitted development rights may be restricted or removed entirely. The same applies if your home is a listed building, which requires listed building consent in addition to any planning permission. Article 4 directions in parts of Rushcliffe Borough, including areas of West Bridgford, can also remove permitted development rights.

Two storey extensions almost always require a full planning application. They are assessed more carefully by local planning authorities because of their greater impact on neighbouring properties — particularly in terms of overlooking, loss of light and the visual character of the street. Newark and Sherwood District Council, Rushcliffe Borough Council and Gedling Borough Council all have clear policies on how two storey extensions are expected to relate to adjacent properties.

This does not mean two storey extensions are harder to achieve - it simply means the design needs to be well thought through from the start. A planning-led approach, which is the basis of everything we do at MO Architects, means considering how the local planning authority is likely to respond before a single line is drawn.

Cost: what should you expect to pay?

Cost is inevitably a major factor. The key principle is straightforward: a two storey extension costs more to build in total, but less per square metre than a single storey extension.

This is because the expensive elements — foundations, roof, external walls — are shared across two floors. You effectively get twice the floor space for significantly less than twice the price.

As a rough guide for Nottinghamshire in 2026:

• A modest single storey extension (15–25 square metres) might cost £35,000 to £65,000 to build, depending on specification and finishes.

• A two storey extension of equivalent footprint (giving 30–50 square metres of total floor space) might cost £60,000 to £110,000 — delivering roughly double the space for around 70–80% more cost.

  
  

Architect fees, structural engineer fees, planning application fees and building regulations costs apply to both. At MO Architects, we charge fixed fees for the planning stage — typically around £950 for a modest single storey extension and £1,450 for a two storey — so you know exactly what you are committing to before work begins.

The value calculation is important too. Both types of extension add value to your home, but a two storey addition — particularly one that adds a bedroom and bathroom - tends to generate a stronger return relative to build cost in the Nottinghamshire property market.

Impact on your garden and outdoor space

A single storey rear extension takes up garden footprint without affecting the first floor. If you have a generous garden and want to maintain outdoor space while improving indoor living, a single storey extension kept close to the house can be a good balance.

A two storey rear extension uses the same garden footprint as a single storey version but adds height. This means it can cast more shadow on the garden - a factor planning authorities pay close attention to. In Rushcliffe and Newark and Sherwood, the impact of a two storey extension on neighbouring gardens and the existing house's own outdoor amenity space forms part of the planning assessment.

If garden space is limited, a side extension - single or two storey - is often worth considering. Many homes in Nottingham suburbs such as West Bridgford, Radcliffe on Trent and Burton Joyce have side access that could accommodate a carefully designed extension without affecting the garden at all.

Which type of extension suits which type of home?

As a general guide:

Single storey extensions work particularly well when:

• You primarily need better kitchen or living space at ground floor level

• Your garden is modest and you want to preserve it

• The property is in a conservation area or is listed, where two storey additions face greater scrutiny

• Your budget is more constrained

• You want to maximise natural light through a well-designed roof lantern or glazed roof

Two storey extensions work particularly well when:

• You need both more ground floor space and additional bedrooms or bathrooms

• You want to maximise value relative to build cost

• Your property has a clear side or rear position where a two storey addition would not harm neighbouring amenity

• You are in an area where two storey additions are common and well-established in the street scene

Many properties in Nottinghamshire — particularly the Victorian and Edwardian semi-detached houses found across West Bridgford, Mapperley, Arnold and Gedling - respond very well to a two storey side extension, which can transform a relatively modest three-bedroom home into a generous four or five-bedroom family house.

The planning-led approach: why it matters

At MO Architects, we always begin with feasibility and planning appraisal before any design work starts. This means we assess your property, your site constraints and the likely planning position before you commit to a direction. It avoids the situation — which is more common than it should be — where a client falls in love with a design that was never going to get planning permission.

With over 350 projects delivered across Nottinghamshire and a 96% planning success rate, we understand how Newark and Sherwood District Council, Rushcliffe Borough Council and Gedling Borough Council approach residential extensions. That knowledge shapes every decision we make from the very first meeting.

If you are considering either a single storey or two storey extension in Nottingham, West Bridgford, Southwell, Newark, Bingham or the surrounding area, our free 15-minute project call is the best place to start. You can also use our planning permission checker to get an initial sense of your planning position before we speak.

MO Architects are ARB-registered, planning-led residential architects based in Nottinghamshire. We work with homeowners, developers and community organisations across Nottingham, West Bridgford, Southwell, Newark, Bingham, Radcliffe on Trent, Burton Joyce and the wider East Midlands.

Call us on 0115 736 5350 or start your consultation here.