Garden Office, Gym and Guest Bedroom Annexe by A Room in the Garden
Published: 25 May 2026
Reading Time: 5 minutes
Many families find that the demands on their home keep growing. A desk in the corner of a bedroom, a spare room that doubles as a gym, relatives sleeping on a fold-out sofa when they visit. This annexe by A Room in the Garden addresses those pressures with a single, well-considered building: a home office and gym for daily family use, and self-contained guest accommodation that works whenever relatives come to stay.
The privacy it creates matters as much as the space. Guests in the annexe have their own entrance, kitchen, bathroom, and sleeping area. The main household carries on undisturbed; nobody has to negotiate who needs the bathroom or when breakfast happens. The building shifts from a working home office and gym during the week to a comfortable, fully self-contained flat at the weekend, without either use requiring any compromise.
A Room in the Garden designed and built the building as a bespoke mobile home, 8.26 metres wide and approximately 34 sqm internally, positioned to occupy the full width of the garden plot.
Designed as a Mobile Home Under the Caravan Act
Permitted Development — the route that allows many garden office and gym buildings to proceed without a planning application — was not available here. The building's height and its position close to the boundary would have taken it outside permitted development limits, and the inclusion of habitable accommodation (a bedroom, kitchen, and bathroom) means that any permanent structure would have required full planning permission and Building Regulations approval.
A Room in the Garden are experienced in designing annexes as mobile homes under the Caravan Act instead. A Lawful Development Certificate confirms the building's status, establishing its legality without a planning application or building control sign-off.
That classification also opened up the design. The Caravan Act permits internal ceiling heights up to 3.05 metres — more generous than permitted development rules allow at this proximity to a boundary. It is the reason the gym wing reaches three metres internally, and why the office section sits at a comfortable 2.44 metres rather than the lower ceiling a more restricted route would have produced. The building is finished to the same standard A Room in the Garden bring to all their projects; the absence of building control sign-off has no bearing on the quality of specification.
Boundary to Boundary on an Angled Site
The rear boundary of the garden does not run in a straight line parallel to the house — it angles across the plot. A Room in the Garden brought the building to the boundaries on all sides, the rear wall following that angle directly. At 8.26 metres wide and approximately 34 sqm internally, the building occupies the full width and length of the available space, with no wasted or inaccessible ground behind it.
Inside, the angled rear wall has been absorbed entirely. The kitchen layout, cabinetry, bathroom tiling, and shelving all follow the acute angle without the visual tells that usually reveal an irregular building — no awkward corners, no sense that anything has been fitted around a problem. The quality of A Room in the Garden's detailing in this respect is particularly notable.
Two Heights for Two Distinct Volumes
The building presents as two connected forms with clearly different heights. The right-hand wing, housing the gym — and doubling as bedroom and bathroom when guests are staying — is 3.46 metres wide and rises to 3.3 metres externally, giving a three-metre floor-to-ceiling height. The left-hand section, containing the office and kitchen, is 4.58 metres wide and sits at 2.69 metres externally, with a 2.44-metre ceiling internally.
Under Permitted Development, achieving either of those heights this close to a boundary would have been difficult. Building under the Caravan Act removed that constraint, allowing A Room in the Garden to size each zone to suit its use rather than defaulting to a single, lower profile across the building.
Externally, the taller gym wing is finished in bold timber cladding, the boards running horizontally before transitioning to vertical as they frame the large fixed picture window. The lower main section is rendered in white, tying in with the main house. Metal cladding to the sides and rear adds durability and keeps maintenance low.
A Wraparound Corner Skylight and Garden-Facing Glazing
With the building sitting boundary to boundary at the rear, all meaningful glazing faces forward onto the garden from the front elevation. A Room in the Garden has made careful use of that constraint.
In the gym wing, an oversized picture window sits within the vertical timber frame and looks directly out onto the garden. In the main living and office space, a sliding door and a full-height tilt-and-turn window are positioned to the left. Above this window, a skylight has been set so the vertical glazing of the window and the horizontal plane of the skylight flow continuously into each other — a wraparound glass corner that brings sky and garden into view at the same time. It is a glazing configuration we have not encountered in other garden room or annexe projects, and it reflects A Room in the Garden's approach to designing around the specific conditions of each site rather than applying a standard solution.
A second skylight over the desk area draws natural light into the rear of the building where the walls provide none. The bathroom also benefits from its own window — oversized for the use, and effective in a room that could otherwise be poorly lit.
Sliding Panels and a Flexible Interior
The main living space contains what reads at first glance as a large slatted feature wall. These are tall sliding panels in oak — acoustic doors that can be drawn aside to open the rooms to each other, or kept closed so the living space functions as a self-contained room without the gym or sleeping zone beyond. The ability to configure the building's zones for work one day and guests the next suits a household with changing requirements throughout the week.
Engineered flooring runs continuously from the gym through to the office and kitchen, reinforcing the sense of one connected building across its two volumes.
The L-shaped kitchen makes good use of its compact footprint. Sand-coloured cabinetry and integrated appliances are arranged efficiently, and despite the angled rear wall behind, the kitchen reads as practical and uncompromised. Access to the bathroom is through a pocket door that slides into the wall rather than swinging into either room — a small decision that keeps both spaces flexible and preserves usable wall area in each.
A Well-Executed Bathroom
The bathroom has the ceiling height that the Caravan Act classification has helped to deliver, and the room is more generous for it. Large marble-effect tiles cover the walls, and black fixtures throughout — taps, towel rail, and the curved shower enclosure frame — contrast with the white marble surface to give a sharp, contemporary finish.
A concealed toilet and the curved shower cubicle with its black-framed glass panels demonstrate how A Room in the Garden has resolved the acute angle of the rear wall without improvisation. The tiling, in particular, is a piece of detailing that would present challenges in any bathroom; the fact that it reads as straightforward and considered reflects the standard of finish the team brings to bespoke work.
Full Turn-Key From Design to Handover
A Room in the Garden managed the entire project: from initial design consultation and the Lawful Development Certificate application through to a completed building, connected to the house services and ready to move into. The team also completed the landscaping — a composite decking area and path with integrated LED lighting connecting the building to the main house, a tiled paving edge to frame the lawn, and horizontal timber fencing panels that echo the exterior cladding and improve privacy at the boundary.
Learn More
A Room in the Garden are based in Brighton & Hove and design and build garden rooms and self-contained annexes across Sussex and the wider UK — both as mobile homes under the Caravan Act and as permanent annexes with full planning permission. To find out what is possible on your site, visit aroominthegarden.co.uk, call 01273 80 70 77, or email hello@aroominthegarden.co.uk.
