Two-storey extension planning and design
A two-storey extension adds living space below and a bedroom or bathroom above. Because the impact on neighbours and the street is greater, these schemes are assessed more closely and most of them need planning permission.
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What these projects typically achieve
- An extra bedroom, often with an en-suite
- A larger kitchen, dining or living room underneath
- A better layout without moving house
What the council assesses
- Scale and proportion relative to the original house
- Effect on neighbouring light, outlook and privacy, including overlooking from new windows
- Distance to boundaries and to the rear of the property
- Roof form, materials and how the addition reads from the street
The planning route
Permitted development does allow certain two-storey rear extensions, but the limits on depth, height and distance to the rear boundary are tight and several conditions apply. In practice a householder planning application is the usual route, and it needs a scheme designed with neighbour impact in mind.
Who this is for
- Families who need an additional bedroom as well as living space
- Homeowners weighing a two-storey extension against moving
- People whose single-storey idea has grown and now needs reassessing
Typical process
- Free planning check on the property and proposal.
- Free 15–20 minute call to discuss the brief and feasibility.
- Written quote before any paid work.
- Design, drawings and the planning application.
- Measured survey, structural calculations and building regulations drawings where included in the package you choose.
Important things to be aware of
- Two-storey work usually has structural implications and will need structural design at the technical stage.
- Overlooking and loss of light are common reasons for objection and refusal, so the design has to address them.
- Foundations, drainage runs and party wall matters often affect what is buildable as much as planning does.
Frequently asked questions
- Are two-storey extensions harder to get approved?
- They are assessed more closely than single-storey work because their impact is greater. A well-considered design that respects neighbours and the existing house gives the application the best footing, but the decision is the council's.
- Do I need a structural engineer?
- Almost always, at the technical stage. We coordinate the structural calculations with the technical drawings. This work is included in the Planning & Technical Design and Planning to Tender packages.
- Can the upstairs windows be a problem?
- New first-floor windows facing a neighbour are a frequent concern. Obscure glazing, repositioning or high-level glazing are common ways a designer addresses it.
Related pages
Official sources
Tell us about your project
Tell us about your property and what you would like to change. We review the enquiry and you can request a free 15–20 minute call to talk it through. We help homeowners in Hampshire, Surrey and Berkshire.
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