Service
House Extensions
A house extension adds new internal floor area to your existing home, typically a rear, side, or wraparound addition. AVA Home Design takes a house extension from feasibility and concept design through planning approval, technical drawings and the build, working across London and the Home Counties.
House extensions are the most common project we work on. Most of our clients want a larger, brighter rear of the house: an open-plan kitchen, diner and living space that opens onto the garden, without leaving their street, their school catchment, or their neighbours.
We design extensions that respect the existing house, sit well with the neighbours, and have a high chance of being approved first time.
Types
- Rear extensions
- Single or double storey, full width or to one side. The most common way to add open-plan living space at the back of the house.
- Side extensions
- Building into the side return, usually a kitchen widening, or a more substantial side addition where the plot allows.
- Wraparound
- A combined rear and side extension, joined at the corner. Powerful for opening up the ground floor without losing too much garden.
- Double-storey extensions
- Adding a bedroom upstairs at the same time as the kitchen below. Stricter planning rules apply.
- Side returns
- The infill alongside a Victorian or Edwardian terrace. Often within permitted development for one storey.
- Porches
- A small front entrance addition. Usually permitted development if under 3 sqm and 3m high.
Frequently asked questions
- Do I need planning permission for a rear extension?
- Many single-storey rear extensions fall within permitted development if they don't exceed 50% of the land around the original house, are no taller than 4m, and don't extend more than 3m beyond the original rear wall (attached houses) or 4m (detached). Larger extensions, double-storey extensions, and houses on designated land usually need a full planning application. We assess this on the first call.
- How long does a house extension take?
- Design and planning typically take 10 to 14 weeks: 1 to 2 weeks for concept, 8 weeks for the planning decision, plus revisions if needed. Construction is usually 12 to 20 weeks for a single-storey extension. The full programme from first call to handover is around six months.
- Which councils have you worked with for extensions?
- We have submitted and gained approvals for extensions in Hillingdon, Harrow, South Bucks, Slough, Ealing, Hounslow, Spelthorne, Watford, Barnet, Brent and Chiltern. Each council reads applications differently and we draw plans that match what they look for.
- What does a rear extension cost?
- Design fees are quoted as a fixed price after the first call once we know the scope. Construction costs vary widely by specification, but homeowners in West London typically budget from £2,500 per square metre for a finished extension at a mid-market specification.