When you need space on both floors, a double storey extension delivers more room per pound than any other type of build. The foundations, groundwork, and roof serve two floors rather than one, which means the additional first floor costs significantly less than building it as a separate project. You get a larger kitchen-diner or living space on the ground floor and extra bedrooms or bathrooms above — all from a single build programme with one team managing every trade.
We design and build double storey extensions across Horsham, handling structural design, planning applications, and the full construction process from foundations through to finishing. Every double storey extension requires careful design to complement your existing property’s proportions, materials, and roofline, and careful management of the planning process to satisfy both Horsham District Council and your neighbours.
Our service covers the complete project — groundwork, steelwork, brickwork, roofing, plastering, electrics, plumbing, and all finishing on both floors. Contact us to discuss a double storey extension at your Horsham home.
A double storey rear extension is the most common two storey project we build across Horsham. The ground floor typically creates a spacious kitchen-diner or enlarged living area while the first floor adds one or two bedrooms, a bathroom, or an ensuite directly above. The extension projects outward from the rear wall, with the new roof tying into the existing structure at ridge or eaves level depending on the design. The rear elevation changes significantly, but the front of the house stays the same. Most double storey rears in Horsham extend between three and five metres deep, delivering twenty to forty square metres of additional space across the two floors — enough to transform a three bedroom house into a comfortable five bedroom family home.
Where plot width allows, a double storey side extension adds space alongside the existing house rather than behind it. This approach suits detached properties and wider semis across Horsham — particularly the family housing in Roffey, Littlehaven, Broadbridge Heath, and Southwater where plots are generous enough to accommodate building to the side without dominating the streetscape. A double storey side extension can add a new ground floor room — a study, utility, or additional reception — with a bedroom or bathroom above. Planning requirements include maintaining a minimum one metre gap to the boundary on detached properties and ensuring the new roofline sits subordinate to the original house to avoid an overbearing appearance.
An over-structure extension builds a new first floor above an existing single storey element of the house — typically above a garage, a ground floor extension, or a single storey side return. This approach adds first floor space without extending the building’s footprint at ground level, making it ideal where garden space is limited or where the ground floor layout already works but the first floor needs additional rooms. The existing ground floor structure must be assessed to confirm it can support the additional load — if the foundations and walls are adequate, the new first floor is built directly above. If they’re not, strengthening work is carried out before the upper storey is constructed.
Sometimes the ground floor provides all the space you need but the first floor is where the house falls short — not enough bedrooms for a growing family, no ensuite for the master bedroom, or a bathroom that the whole household shares when two would transform the morning routine. A first floor addition extends above the existing ground floor footprint, adding rooms at bedroom level without altering the ground floor layout. We design first floor additions across Horsham that match the existing roofline, brickwork, and window proportions, creating an extension that looks like it was always part of the property. Structural assessment ensures the existing ground floor supports the additional load safely and to Building Regulations standards.
A double storey extension is structurally more complex than a single storey build. The foundations carry greater loads, the steelwork spans are larger, the roof connection to the existing house needs careful detailing, and the first floor structure must integrate seamlessly with the existing building. Getting these elements right requires experience with two storey construction and the structural understanding to deliver a build that’s safe, compliant, and built to last.
We provide detailed quotes covering every element of the double storey build — foundations, brickwork, steelwork, roofing, first floor structure, plastering, electrics, plumbing, flooring, and decoration across both floors. You know exactly what the project costs before we break ground, and if anything changes during the build we discuss it openly before proceeding.
We build double storey extensions throughout Horsham and the surrounding area, covering the town centre, Roffey, Littlehaven, Holbrook, Trafalgar, Broadbridge Heath, Southwater, Billingshurst, Pulborough, Storrington, Henfield, Steyning, and surrounding West Sussex villages.
If you need first floor space but don’t want to extend outward, a loft conversion adds a room above without changing the building’s footprint. We carry out Velux, rear dormer, and hip-to-gable conversions across Horsham, handling structural steelwork, insulation, staircase installation, electrics, plumbing, and finishing. Most conversions proceed under permitted development. A loft conversion is sometimes a more cost-effective route to an additional bedroom and ensuite than a double storey extension, particularly on properties where extending outward is restricted by plot size, boundary distances, or planning constraints.
A double storey extension often includes a new kitchen on the ground floor and a new bathroom above — and having one team manage the extension build and the interior fitting means seamless coordination between the two. We carry out complete kitchen and bathroom renovations across Horsham, handling strip-out, structural work, plumbing, electrics, tiling, flooring, and expert fitting. We install kitchens from any supplier and coordinate every trade in sequence. Bathroom work covers full installations, wet rooms, and ensuites with thorough waterproofing behind every tiled surface.
A double storey extension is often part of a wider transformation — extending the house while renovating the existing rooms to match the new space. We handle building work that crosses trade boundaries, covering structural alterations, wall removal, rewiring, replumbing, plastering, flooring, and decoration alongside the extension build. Having one team manage both the extension and the renovation ensures consistent quality throughout the house rather than a beautiful new extension connected to tired existing rooms. Whatever the scope across your Horsham property, we coordinate the full programme from start to finish.
Not sure what’s possible with your property? Call our Horsham team to arrange a free visit and discuss your options.