Studio and open-plan granny annexes: layouts, sizes and floor plans
A studio annexe, also called an open-plan annexe or a garden studio flat, is a self-contained garden annexe where living, kitchen and sleeping share one main room and only the shower room has walls of its own. Without partitions, the building feels larger than its floor area suggests, and it is the layout that fits a complete home into the smallest footprint: across the projects on this page, from under 20sqm.
Illustrated from a scale model by The Garden Room & Annexe Guide.
In short
- Layout: living, cooking and sleeping in one room, with a separate shower room. Furniture, half-height walls, sliding panels or a curtain define the zones instead of full walls.
- Size: it works from around 20sqm. At that size a double bed, a kitchenette and a shower room all fit; by 25–30sqm there is room for a full kitchen and a proper sitting area.
- Cost: budget around £50,000–£75,000 for a compact studio building, and £65,000–£95,000 once groundworks and connections are added.
- Planning: a studio annexe is still a home, so it needs the same consent route as any other annexe: full planning permission, or the Caravan Act route with a Lawful Development Certificate.
What is a studio annexe?
A garden annexe laid out like a studio flat: one main room for living, cooking and sleeping, and a shower room behind its own door.
Everything needed for independent day-to-day living is there: a kitchen or kitchenette, a bathroom and somewhere to sleep. What it leaves out is the internal walls between them.
That single decision does most of the work. With no corridor and no doors to swing, every square metre is usable, and the eye travels the full length of the building to the glazing at the far end. A 25sqm studio feels noticeably larger than a 25sqm building divided into two small rooms, and one open room is simpler to heat and to light.
The trade-off is privacy. Sleeping in the same room as the kitchen and the sofa suits one person, or a couple who are comfortable with it, better than it suits a household that keeps different hours. Most of the design effort in a studio goes into giving the bed a sense of its own space without closing the room down.
Studio and open-plan annexes built by UK companies
Every studio and open-plan annexe featured on The Guide, in a random order: permanent buildings with full planning permission and Building Regulations sign-off, and annexes built as mobile homes under the Caravan Act with a Lawful Development Certificate.
5 Sided Garden Annexe
Executive Garden Rooms designed a unique five-sided garden annexe with no 90-degree corners, maximising space and functionality. This 30sqm, self-contained home features an open-plan layout and pressurised water system. Supplied on a turnkey basis including planning services and groundworks.
Accessible Open-Plan Garden Annexe
A Room in the Garden designed a 6.6m x 7m accessible garden annexe featuring an open-plan layout. The one-bedroom home incorporates personalised elements, including a stained glass window. With a fully accessible shower room and low-maintenance exterior, it offers independent living tailored to the client’s needs.
Garden Office, Gym and Guest Bedroom Annexe by A Room in the Garden
This annexe by A Room in the Garden delivers a home office, gym and self-contained guest accommodation in one garden building — giving a busy family the space they need and genuine privacy for everyone on the property.
En-Suite Garden Bedroom
This en-suite garden bedroom by Annexe Spaces provides a functional, stylish extension alternative, featuring a low-maintenance Silicon K-Render finish. The design includes a spacious bedroom and shower room with new-build interiors, creating seamless indoor-outdoor living.
Guest Bedroom in the Garden
Building a garden bedroom is an efficient alternative to a home extension. This 6m x 4.3m self-contained annexe by Executive Garden Rooms features an en-suite shower room, kitchenette, and high-spec finishes. Their turnkey service covers design, construction, and regulatory compliance.
Annexxa 635 by Garden Annexes: Open-Plan Living in a 31sqm Footprint
This Annexxa 635 by Garden Annexes packs open-plan living, a well-appointed kitchen, en-suite shower room and flexible sleeping into a 30.9sqm footprint. Wide-board cladding, shadow gap detailing, and a soft blue-grey palette make for a compact annexe with considered architectural character.
One Person Granny Annexe
Executive Garden Rooms designed a 6m x 4m one-person granny annexe, showcasing a compact yet functional home. It features a combined living/sleeping area, kitchen with instant hot water, and a spacious shower room. The sedum roof adds insulation and visual appeal.
29.4sqm Open-Plan Ivyo by Garden Annexes
This 29.4 sqm open-plan Ivyo 540 by Garden Annexes is finished in Midnight Black with a vaulted ceiling, exposed trusses and zoned living, kitchen and bedroom space. En-suite shower room and a full turnkey handover, including groundworks and services.
Studio or one-bedroom annexe, and where a garden bedroom fits
The three smaller layouts overlap in size, and companies use the names loosely. What separates them is how much of daily life happens in the annexe, and whether the bedroom has a wall.
- Garden bedroom · usually under 25 sqm
- A bedroom with its own shower room, with no kitchen or only a small tea station. Suits guests, or a relative who eats and spends the day in the main house.
- Studio / open-plan · 20–51 sqm across our projects
- Living, kitchen and sleeping in one room, plus a shower room. A kitchenette at the smallest sizes, a full kitchen from around 25–30sqm. Suits one person living independently, or a couple.
- One-bedroom · typically 31–55 sqm
- A separate bedroom, a living-kitchen and a bathroom, usually with a full kitchen. Suits one or two people who want the bed in a room of its own.
The line between a studio and a one-bedroom annexe usually falls somewhere between 25 and 35sqm. Below that, a separate bedroom tends to leave both rooms cramped. Above it, a designer can add a wall with a pocket door and still keep a comfortable living area, and many buyers choose to. Plenty do not: several of the larger projects on this page stayed open-plan at 40–51sqm, two of them so that a wheelchair user could move freely through the whole building.
What does a studio granny annexe floor plan look like?
A double bed, a kitchenette and a shower room fit in a studio annexe of around 21sqm, such as a 6m × 3.5m building with roughly 17sqm of floor inside. From about 25–30sqm there is room for a full kitchen and a separate sitting area as well.
The plans in this section are drawn to scale from models built by The Guide and furnished with standard UK furniture sizes, so what fits on the plan fits in the building. The illustrations alongside them are made from the same models.
In a studio the floor plan is essentially one room, so it comes down to three decisions: where the shower room goes, where the kitchen runs, and how the bed relates to the rest of the space. The positions of the kitchen and bathroom drive much of the layout, because they need water and drainage and are the hardest things to move once the design is fixed.
Can you fit a double bed, a kitchen and a bathroom into 20–25sqm? Yes, and several projects on this page do exactly that. Ark Design Build’s annexe in Esher is 19.84sqm, 3.2m by 6.2m, with a kitchenette and an en-suite shower room alongside the main room. Executive Garden Rooms fitted a double bed, storage, seating, a kitchenette and a shower room into 25.8sqm on a 6m by 4.3m footprint. At 24sqm they built a one-person annexe where the living area doubles as the bedroom, with a kitchen that takes a combination oven and a washing machine.
A 6m × 3.5m (21sqm) studio: a standard double bed (135cm × 190cm), kitchenette, wardrobe and shower room, with a sofa facing the doors. Plan: scale illustration. Interior: illustrated from the same scale model. By The Garden Room & Annexe Guide.
Footprint and floor area are not the same. The sizes quoted for annexes are almost always external. Walls built to a residential standard are thick, so the usable floor inside is smaller: Garden Annexes’ Ivyo 540 has a 29.4sqm footprint and about 24sqm inside, and their 30.9sqm Annexxa 635 gives about 26sqm. When comparing a floor plan with a company’s price list, check which figure each one uses.
Layout points that recur at the smallest sizes
- The shower room across one end of the building is the most space-efficient arrangement, because it leaves the rest of the room as one clear rectangle.
- A kitchen along a single wall keeps the floor open. An L-shaped kitchen gives more worktop but takes a corner the bed or sofa might have used.
- Putting the bed at the end furthest from the entrance means visitors arrive in the living area rather than beside the bed.
- A sofa bed in place of a fixed bed, as the owner of the Annexxa 635 chose, turns the whole room into living space during the day.
- On a narrow plot, the rooms line up along the length of the building. Ark Design Build’s Esher annexe is only 3.2m wide, with the shower room at one end and the living and sleeping space running towards the glazing.
- A long, narrow building suits a narrow garden. The same 28.8sqm as the 6m × 4.8m studio can be laid out 8m long and 3.6m wide, with the glazing at the garden end and the zones in a line behind it.
- An L-shaped plan separates the zones without any internal walls. In Annexe Spaces’ 51sqm annexe, the shower room sits in the corner of the L and the sleeping area in one arm, out of sight of the living space in the other.
The same 28.8sqm for a narrow garden: 8m × 3.6m, with living by the glazing, the kitchen along one wall, the bed behind a half-height wall and the shower room across the far end. Plan: scale illustration. Exterior: illustrated from the same scale model. By The Garden Room & Annexe Guide.
How to zone an open-plan annexe
Without full walls, the zones in a studio are made by what sits between them. The projects on this page use five approaches, and each gives a different balance between openness and privacy.
- A half-height wallExecutive Garden Rooms used one in a 30sqm five-sided annexe to screen the bed from the kitchen and dining area. Light still crosses the whole room above it, and the bed is out of view from the entrance. The same device zones a 35.1sqm building into areas for relaxing, working and entertaining.
- Sliding panelsIn a 34sqm annexe by A Room in the Garden, oak sliding acoustic panels close the living space off from the sleeping zone. Open during the day, it is one large room; closed at night, it works as a bedroom, with the panels cutting noise as well as light.
- A curtainAnnexe Spaces gave a 51sqm accessible annexe a curtained sleeping zone. It is the simplest option and the least permanent, and in that project it keeps the floor completely clear for a wheelchair.
- Fitted furnitureArk Design Build used built-in joinery to define living, dining and sleeping areas in a 37.5sqm garden apartment, so storage and zoning come from the same pieces.
- A change of levelTimeless Garden Rooms added a raised sleeping deck to a 40sqm teenagers’ annexe, under an asymmetrical roof that gives it the height. Where the roof allows, it takes the bed off the floor plan altogether.
Who a studio annexe suits
A single occupant living independently
The core use: an older parent, a young adult saving for a deposit, or a relative who wants their own kitchen and shower room a few steps from the family, without a larger building than one person needs.
Guests and visiting family
A studio gives visitors a complete place to stay, with more independence than a garden bedroom. Several owners use theirs as an office or gym during the week and as guest accommodation at weekends.
A young adult
Teenagers and young adults tend to value a room they can arrange themselves over a small bedroom and a smaller living room. The priorities to raise with a company are a kitchen that works properly, storage, and hardwired broadband rather than Wi-Fi from the house.
Someone with a mobility need
Open-plan layouts suit wheelchair users and anyone using a walking frame, because there are fewer doorways to pass through and more clear floor for turning.
Two of the larger projects on this page were designed for accessibility for that reason: a 46.2sqm annexe by A Room in the Garden with only one wall, separating the kitchen from a fully accessible shower room, and the 51sqm L-shaped annexe by Annexe Spaces with a wheelchair-friendly shower room and level thresholds out to the decking. If an occupational therapist is involved in the occupant’s care, their recommendations can be written into the brief.
Details that matter more in a studio
- Ceiling heightIn a single room, height does more for the sense of space than anything else. A pitched roof gives a vaulted ceiling across the whole room, which is why several of the projects here use one: exposed trusses lift the ceiling in Garden Annexes’ Ivyo, and exposed timber beams do the same in Ark Design Build’s 30sqm family annexe. Raise ceiling height early; it is straightforward to design in and very difficult to change later.
- StorageUnderestimated in almost every annexe, and more so in a studio, where anything without a cupboard is on show. Built-in wardrobes, a full-height kitchen unit and somewhere near the door for coats and shoes keep the room from filling up.
- Where the light comes fromBig glazing at one end of a long, narrow studio lights the living area and leaves the far end dim. Skylights over the kitchen or the bed, a letterbox window above the sink, as in the Annexxa, or glazing on two sides as in Ark Design Build’s garden apartment, spread the light through the room. Think about the sight line from the main house into the sleeping area, too.
- Pocket doorsIn a studio the only internal door is usually the shower room’s. A pocket door there recovers the floor space a swinging door would need, which matters most beside a bed or a kitchen run. It has to be designed in from the start, because the wall is built around the sliding mechanism.
- Heating and waterOne open room is simple to heat evenly, and underfloor heating keeps the walls free for furniture and kitchen units. A studio still needs a proper hot water system: Executive Garden Rooms fitted a pressurised system in their five-sided annexe so the shower is unaffected by taps running in the main house.
How much does a studio annexe cost?
For a compact studio or open-plan annexe under 25sqm, building prices typically run from around £50,000 to £75,000. Some companies include foundations in the price; where they aren't included, groundworks and utility connections usually add £15,000 to £20,000, and a realistic turnkey budget is around £65,000–£95,000.
- Studio / open-plan · under 25 sqm
- Building prices of £50,000–£75,000; £65,000–£95,000 with groundworks and connections.
- One-bedroom · typically 31–55 sqm
- Building prices of £70,000–£120,000; £85,000–£140,000 with groundworks and connections.
Figures from real projects and 267 published prices from 13 UK annexe specialists, checked October 2026. As a real reference point, a 31.5sqm one-room annexe from a well-regarded specialist has come in at £90,000–£100,000 all-in. Whether VAT is included depends on the planning route.
The planning route affects the price as much as the size does. A studio annexe built to BS3632 and supplied under the Caravan Act may be zero-rated for VAT, while the same building on the full planning route carries 20%. Before comparing two quotes, check what each one includes and whether VAT is in the figure.
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Frequently asked questions
- What is a studio annexe?
- A studio annexe is a self-contained garden annexe with one main room for living, cooking and sleeping, and a separate shower room. It is laid out like a studio flat, with its own kitchen and shower room but no internal walls between the living and sleeping areas. It is also called an open-plan annexe.
- Can a 21sqm annexe fit a double bed, a kitchen and a bathroom?
- Yes. A studio layout of around 20–25sqm can take a double bed, a kitchenette along one wall and a shower room across one end. Projects on The Guide include a 19.84sqm annexe with a kitchenette and en-suite shower room, and a 25.8sqm annexe with a double bed, seating, a kitchenette and a shower room.
- Is a studio or a one-bedroom annexe better?
- It depends on who lives there. A studio makes the most of a small footprint, feels larger than its size and suits one person, or a couple who are comfortable sharing one room. A one-bedroom annexe gives the bed a room of its own, which matters more for a couple who keep different hours, or for a carer staying over. The change usually becomes practical between 25 and 35sqm.
- How big should a studio annexe be?
- Most studio annexes on The Guide are between 20 and 40sqm. Around 20–25sqm fits the essentials for one person; 25–35sqm allows a full kitchen and a separate sitting area. Sizes are usually quoted as the external footprint, and the internal floor area is typically 15–20% smaller once the walls are accounted for.
- How much does a studio annexe cost?
- A compact studio annexe under 25sqm typically costs £50,000–£75,000 for the building. Where groundworks and utility connections aren't included, they usually add £15,000–£20,000, and a realistic turnkey budget is around £65,000–£95,000. Whether VAT is included depends on the planning route, so check each quote.
- Does a studio annexe need planning permission?
- A studio annexe has its own kitchen, bathroom and sleeping space, so it cannot be built under Permitted Development. It needs either full planning permission with Building Regulations, or the Caravan Act route, where the annexe is built to BS3632 and its siting is confirmed by a Lawful Development Certificate.
Illustrated from a scale model by The Garden Room & Annexe Guide.
Find studio annexe specialists that cover your area
The Garden Room & Annexe Directory lists UK companies that build studio and open-plan annexes, filtered by location, planning route and design approach.
Last updated October 2026 · Part of our garden annexe guide.
