West Sussex · RH12, RH13
Annexes in Horsham
An annexe is self-contained living accommodation on the same plot as a main house, complete with its own kitchen and bathroom facilities, built either as a new detached structure, a conversion of an existing outbuilding, or an extension with its own entrance.
In Horsham, that covers Roffey, Holbrook, Littlehaven, Denne, Trafalgar, Broadbridge Heath, Southwater, Warnham, Colgate. Horsham's town centre retains a historic core of timber-framed and Georgian buildings around the Carfax and Causeway, surrounded by Victorian villas, interwar suburbs and newer developments on the town's edges. The surrounding villages and countryside sit close to the South Downs, which shapes both the property styles and the planning context for extension and renovation work.
Coverage
Areas we cover in Horsham for annexes
Property styles in Horsham
Horsham has a strong stock of period cottages and Victorian villas in and around the town centre, alongside 20th-century family housing in the surrounding estates and larger detached homes in the outlying villages. Extension and loft conversion potential varies significantly between the historic core and the more recent suburbs.
Planning considerations
Horsham District Council is the local planning authority. The town centre, including the Causeway, is a conservation area with a number of listed buildings, meaning alterations to visible elevations, windows and materials are more tightly controlled. Some outlying villages also have their own conservation area designations, which we check before advising on likely planning routes.
How it works
Our annexes process
- 01
Feasibility and planning strategy
Assessing the plot, existing structures and local planning policy for ancillary accommodation, and whether a new build, conversion or extension route is best.
- 02
Design and approvals
Preparing drawings, submitting for planning permission (usually required for annexes with independent facilities) and Building Regulations.
- 03
Construction
Groundworks and structure (for a new build), or structural and fabric works to the existing building (for a conversion), followed by full services connections.
- 04
Fit-out and completion
Kitchen and bathroom fit-out, decoration, and Building Control sign-off.
Also in this area
Other services we provide in Horsham
Nearby coverage
Annexes in nearby areas
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FAQs
Annexes in Horsham: FAQs
Do you provide annexes across all of Horsham?
Yes, we cover the RH12 and RH13 postcode areas in full, including Roffey, Holbrook, Littlehaven, Denne, Trafalgar, Broadbridge Heath, Southwater, Warnham, Colgate.
Do I need planning permission for an annexe?
Usually yes, because independent cooking, sleeping and washing facilities mean the structure is not treated as a simple outbuilding. Some annexes intended purely as ancillary accommodation for the main house can fall under permitted development, but this depends on size, position and local policy, which we check during feasibility.
Can an existing garage or outbuilding be converted into an annexe?
Yes, provided the structure is suitable and can be brought up to full Building Regulations standard for insulation, damp-proofing and services. We assess this as part of the feasibility stage alongside a new-build option.
Is Horsham town centre a conservation area?
Yes, the historic core around the Carfax and Causeway is a conservation area with a number of listed buildings, which affects what changes can be made without planning permission or listed building consent.
Get a quote for annexes in Horsham
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Last reviewed 2026-07-28.