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Garden room project · Timber Rooms

Cedar garden office with store and through access for a London garden

A 4.6m × 3.7m cedar garden office in Wimbledon, London, built boundary to boundary, with a hidden store that keeps the route through to the lane behind.


Published 6 June 2026 · 4 minute read · Written by The Garden Room & Annexe Guide

Western Red Cedar has been used on the front elevation paired with dark grey Hardie® Plank composite cladding
Timber Rooms  4.6m × 3.7m garden office in Wimbledon, London

When a house has already had a loft conversion and a flat roof extension, the usual routes to more space have been used up. This terraced house in Wimbledon, London, is a good example of that situation. The answer the clients came to was a garden room, and they chose Timber Rooms as bespoke designers with a lot of experience designing for exactly this sort of situation – adding space at the bottom of the garden rather than disrupting the home again.

The brief was for a building that could do several jobs at once. It is used day to day as a full-time garden office, but it also doubles as a place to hang out and socialise, and as a garden gym. As with Timber Rooms’ other high-spec projects, the intention is everyday, year-round use rather than a seasonal extra, so the room becomes a genuine extension of how the household lives.

At a glance

  • Size: 4.6m × 3.7m, running the full width of the plot at the end of a terraced garden, used as a full-time office, a gym and a place to socialise.
  • Boundary walls: Over 15sqm and within a metre of the boundary, so the side walls are a composite board, finished in the same dark grey as the detailing on the front.
  • Store and through access: A door hidden in the cedar opens into a plywood-lined store with shelving, and a multi-point locking door at the back opens onto the lane.
  • The front: Vertical Western Red Cedar with the wall set back two boards deep, the recess picked out in anthracite composite, downlights in the canopy and aluminium bi-folds.
  • Company: Timber Rooms, whose turnkey service included the electrical connection to the house by their in-house team.

Part of our garden office guide →

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The plot

Filling the plot without losing the lane

A garden room that fills the back end of the plot is one of the smartest ways to add space to a London terrace, and this 4.6m x 3.7m building runs from boundary to boundary to make the most of the available width. But maximising the end of a garden like this raises a practical question that is easy to overlook: many terraced houses rely on an alley or lane behind the property for access, and a building that fills the plot can block it.

This is where working with a bespoke designer like Timber Rooms earns its place. Rather than choosing from a fixed range of sizes and accepting whatever access is left over, the building was designed to maintain the through route from the start. The result is extra living space and valuable storage without giving up the access the client needed – a solution tailored to the plot rather than forced onto it.

Regulations

Building to the boundary

Building right up to the boundary brings a regulation to be aware of. Where a garden building is larger than 15m2 and positioned within one metre of a boundary, it needs to be constructed largely from non-combustible materials. At 4.6m x 3.7m this building is over that threshold, so the boundary-facing walls had to be handled accordingly.

This is the kind of detail Timber Rooms are very experienced with, and the solution is a neat one. On the boundary-facing walls they have used a composite board – they usually specify Hardie® Plank for this – finished in the same smart dark grey as the recessed detailing on the front elevation, so the practical requirement is tied visually into the rest of the design rather than looking like an afterthought. As well as satisfying the building regulation, the composite offers a long, maintenance-free lifespan on exactly the kind of walls that are difficult to reach and maintain once the building is in place against the boundary.

The front

A recessed front in cedar and composite

The front of the building is clad in Western Red Cedar tongue and groove, fitted vertically, which gives the front a clean, upright rhythm. The detail that lifts it, though, is the recessed front elevation: the front wall is set back two boards deep, creating a strong, deep shadow line across the elevation, with downlighting fitted into the canopy section so the building reads well after dark as well as during the day.

That recess has been neatly picked out in anthracite grey composite cladding, which offers a sharp contrast against the warm cedar and complements the aluminium bi-fold doors that lead into the office. The combination of natural timber and dark composite is what gives the front its striking, considered look.

The front wall has been recessed to create a stylish cheek and canopy detail
The recessed front  forming a cheek and canopy detail
Storage

A secret store with through access

The building is split into two parts: the main room, which carries the office, gym, and entertaining uses, and a separate store. A store room is always useful, and especially so on a plot with no space for a shed and no garage. Designing the storage into the building itself is a far more attractive use of space than a traditional outbuilding, and here it has been handled with real care.

A second door on the front elevation, beautifully detailed so it blends almost invisibly into the wall of cladding, leads into the store. From inside, a second door at the rear of the building opens onto the pathway behind the property, providing the through access the client required. While the front store door is kept secret behind the cedar, the rear door is a house-quality, multi-point locking solid door, as you would want for a door opening onto a public lane.

Inside, the store has been lined in durable plywood, which suits a working storage space far better than the plastered and decorated, house-quality finish of the main room next door. Bespoke shelving units run along the left-hand wall to maximise household storage, while leaving a clear route of access between the two doors so things can be moved straight through from garden to alley.

Inside the storage room showing the through access to the lane behind the property
Inside the store  with the through access to the lane
Everyday use

One room, several daily uses

For much of the working week the main room functions as a full-time office, which means it has to be comfortable, well lit, and quiet enough to concentrate in. Outside of work it takes on other roles – there is a gym area, and a dartboard hints at the more social side of how the family uses the space.

With the bi-fold doors slid to one side, the room opens up and the boundary between house, garden, and building dissolves, bringing the whole space together. When the doors are closed, the multi-layer build-up of the insulated timber frame core that Timber Rooms specialise in keeps the room comfortable to use right through the year, so none of those uses are limited to the warmer months.

Inside the office room with its plastered and decorated interior
The office  plastered and decorated
The bi-folds slide to one side to create an easy indoor-outdoor connection
The bi-folds  slid to one side
Turnkey

Turnkey delivery and in-house electrics

Timber Rooms offer a turnkey service, which on a project like this includes the electrical connection between the garden office and the house. Because the electrical work is handled by their own in-house team, the specification can be tailored around how the room will actually be used – socket positions, lighting, and any data or audio-visual requirements planned around where the desk, the gym kit, and the seating sit, rather than fitted as an afterthought.

Planning something similar?

Learn more about Timber Rooms

Timber Rooms design and build bespoke garden rooms across Sussex, Surrey, and South London, with each project shaped around the client, the plot, and how the space will be used. To discuss your own project or explore more of their work, visit www.timberrooms.co.uk, call 01273 839 491, or email hello@timberrooms.co.uk. We have also featured several other Timber Rooms projects on The Guide.

Visit Timber Rooms More Timber Rooms projects
More projects like this Garden offices Multi-use offices Garden rooms with storage Garden gyms Composite cladding 10–20sqm garden rooms
Read the guides What garden rooms cost Permitted development Buying a garden gym

Published 6 June 2026 · Photographs courtesy of Timber Rooms.

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