A single storey extension looks the same on paper whether it sits behind a semi-detached house or behind a corner cafe. A box is added, a wall comes down and daylight comes in.
The similarities stop there. A home project follows household planning rules, while a business project is judged on how the space will be used. This guide compares the two, so you know which rules apply before you commission drawings for a single storey extension.
How Does a Single Storey Extension Differ Between Home and Business?
Quick answer: A home extension is usually judged against permitted development limits and neighbour impact. A business extension is judged on its use class, safety, accessibility and effect on the street. Both need building regulations approval, but commercial projects face more checks, so confirm which category applies first.
The core question changes. At home, you ask how much space you can add. In a business, you ask what the space is for, who will use it and what the council expects of that use.
Planning at Home: Permitted Development and Its Limits
Many houses can add a single storey rear extension without a full planning application. The standard depth is up to 3 metres on a terraced or semi-detached house and 4 metres on a detached one. A deeper extension, up to 6 and 8 metres, can go through the neighbour consultation route.
Height matters too. Within 2 metres of a boundary, the eaves generally cannot exceed 3 metres. Flats, maisonettes and homes in conservation areas need full planning permission, and Article 4 Directions can remove these rights on some streets. Check your exact address before you assume anything. Permitted development limits are measured from the original house, so earlier extensions by previous owners can use up part of your allowance. A look at the property’s planning history avoids an unpleasant surprise.
Planning for a Business Premises: Use Class and Permission
Business premises have far narrower permitted development rights than houses. Some non-domestic buildings have limited allowances, but a shop, cafe, office or clinic extension usually needs planning permission, and the council will look at the use class, the size of the addition and the effect on neighbours and the street.
Use class is the starting point. Shops, restaurants, offices and clinics sit within the same broad commercial class, but pubs and takeaways are treated differently. If your extension also changes how the space is used, you may be dealing with a change of use as well as a physical addition. A commercial architect can confirm both questions early, before drawings are produced.
Tenants should also check their lease. Most leases need the landlord’s consent for structural alterations, and that conversation can take longer than the planning process.
Building Regulations and Safety: Where the Gap Widens
Both types of project need building regulations approval, covering structure, fire safety, insulation, drainage and ventilation. A homeowner usually deals with building control alone.
A business premises carries more duties. Fire safety rules for non-domestic buildings require a fire risk assessment, clear escape routes and suitable alarms. Accessibility also matters, because customers or staff may need step free entry, suitable doors and accessible toilets. A restaurant extension may need kitchen extraction, which affects roof layout and neighbours. These requirements shape the design from the start, not after it.
Design and Layout: Living Space vs Customer Space
At home, a single storey extension usually becomes a kitchen diner, a family room or a home office. Priorities are daylight, a connection to the garden and the flow between old and new rooms.
In a business, the layout follows the customer journey. A cafe needs seating, a counter and a service route, while a clinic needs private rooms and a reception. Materials need to be hard wearing, and signage, shopfront and glazing are all judged by the council.
A practical tip applies to both. Before design begins, write a one page brief listing who will use the space, at what times and how many people at once. That single page prevents most layout changes. Share it with the architect at the first meeting, and update it if your plans for the space change.
Who Should You Hire for Each Project?
For a home project, look for a practice that knows your borough, submits applications regularly and handles building regulations and structural design. For a business project, add experience of change of use, accessibility and fire safety.
Extension Architecture covers both. Its commercial page lists planning applications, detailed plans, oversight of construction and interior design, and its case studies include cafes and restaurants in areas such as Kingston and Richmond. The same in-house team of architects, planning consultants, interior designers and structural engineers handles the work, so planning, design and engineering sit together.
Neighbours matter in both cases. Homeowners may need party wall notice, while a business next to residential flats may face objections about noise, opening hours or extraction, so early conversations help. Whichever route you choose, ask each practice for examples of similar projects and what the council decided. A clear answer on that point is the quickest way to judge experience.