Rear extensions and side returns
A single-storey rear extension is one of the most common ways to add a larger kitchen or living space, while a side-return extension fills in the narrow strip of garden alongside a house, often used on terraced and semi-detached properties to open up an existing kitchen.
Permitted development and planning permission
Many single-storey extensions fall under permitted development, subject to limits on depth, height and how much of the garden is built over, though these limits are tighter for terraced and semi-detached houses than for detached ones, as the Planning Portal's extensions guidance sets out. Where a project goes beyond those limits, a full planning application is needed, and Horsham District Council or Crawley Borough Council can confirm what applies to a specific property.
Party walls and neighbours
Where an extension is built on or near a boundary, or affects a shared wall, the Party Wall etc. Act 1996 sets out a formal process for notifying neighbours and resolving any disagreement before work starts. GOV.UK's guidance on the Act explains when a notice is needed and what it should cover.
Foundations and matching materials
Foundation depth depends on ground conditions and anything nearby, including trees, whose roots can affect how the soil behaves. Matching brick, render or roof tiles to the existing house is usually part of the design discussion with an installer, particularly where the extension is clearly visible from the street.
Frequently asked questions
Do I need planning permission for a rear extension?+
Often not, if it stays within permitted development limits, but these limits depend on your house type and how much has already been built. Check with Horsham District Council or Crawley Borough Council for your specific property.
What's a side-return extension?+
It's an extension that fills the narrow side passage alongside a house, commonly used on terraced and semi-detached properties to open up a kitchen or living space.
Will I need to notify my neighbours?+
If the extension is built on or near a shared boundary or affects a party wall, the Party Wall etc. Act 1996 may require formal notice, which is worth raising with your installer early.
Useful local links
- Crawley Borough Council – Planning — The planning authority for Crawley, which sits outside the Horsham district boundary.
- GOV.UK – Planning permission: when you need it — Government guidance on when planning permission is required in England and Wales.
- GOV.UK – Party Wall etc. Act 1996 guidance — Government guidance on notifying neighbours and resolving disputes over shared or boundary walls, relevant to attached garage conversions.
- Planning Portal – Garage conversion — National guidance on when planning permission is needed for a garage conversion in England.
- Planning Portal – Extensions — National guidance on permitted development rules for single-storey house extensions.
- Planning Portal – Outbuildings — National guidance on permitted development rules for garden buildings and outbuildings, including height and coverage limits.