Garden Room Planning rules

Outbuildings are considered to be permitted development, not needing planning permission, subject to the following limits and conditions:

  • No outbuilding on land forward of a wall forming the principal elevation.
  • Outbuildings and garages to be single story with a maximum eaves height of 2.5 metres and maximum overall height of four metres with a dual pitched roof or three metres for any other roof.
  • Maximum height of 2.5 metres in the case of a building, enclosure, or container within two metres of a boundary of the curtilage of the dwellinghouse.
  • No verandas, balconies, or raised platforms (a platform must not exceed 0.3 metres in height)
  • No more than half the area of land around the “original house”* would be covered by additions or other buildings.
  • In National Parks, the Broads, Areas of Outstanding Natural Beauty, and World Heritage Sites the maximum area to be covered by buildings, enclosures, containers, and pools more than 20 metres from the house is limited to 10 square metres.
  • On designated land* buildings, enclosures, containers, and pools at the side of properties will require planning permission.
  • Within the curtilage of listed buildings, any outbuilding will require planning permission.

*The term “original house” means the house as it was first built or as it stood on 1 July 1948 (if it was built before that date). Although you may not have built an extension to the house, a previous owner may have done so.

*Designated land includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas, and World Heritage Sites.

Please note: The permitted development allowances described here apply to houses and not to:

  • Flats and maisonettes (view our guidance on flats and maisonettes
  • Converted houses or houses created through the ‘permitted development’ rights for:
  • Other buildings
  • Areas where there may be a planning condition, Article 4 Direction or other restriction that limits permitted development rights.

More details here

Garden Room Height

What is the Garden Room’s maximum Height?

For a Garden Room to be built under permitted development and avoid planning permission, The maximum height must not exceed 2.5 metres, This is measured from the highest part of the Garden Room to the highest piece of land directly next to the building.

This does limit the internal height of the building because you need to insulate the roof void and the floor.

Garden Room Cost

How much does a Garden Room Cost?

The Cost of a modern, weather-tight, and insulated Garden Room that can be used all year round would change hugely depending on the specifications and size.

A basic and small Garden Room e.g. 3x3M could be built for under £5,000, provided you can do most of the work yourself and use budget items like UPVC french doors instead of Aluminium Bi-fold doors.

A larger Premium Garden Room could easily cost £10,000 and beyond to build.

DIY Garden Room

Can I build my own Garden Room?

Building your own garden room requires a good level of DIY knowledge and access to several power tools (see our list of required tools), Ideally, it is a job for at least 2 people and could take around 15 working days from start to finish, depending on your skill level.

See our step-by-step guide to see what is involved


What is the lifespan of a garden room?

The life span of a garden room will mainly depend mainly on the quality of the construction materials.

Garden rooms vary in price from £3000.00 to £30,000.00. A cheap garden room should last a few years at least but a well-constructed garden room should last between 30-40 years or even longer.

Garden Room Doors and Windows

Garden Room French doors are the cheapest option for your garden room. Both doors open outwards into the garden, meaning you don’t need to leave space for the swing of the door inside the room. You can open just one door for day-to-day access or both doors if you want to open up the room onto the garden. The reveals in the door frame may stop the doors from opening further than 90 degrees though.

Long windows often accompany French doors on either side. These sidelights vary in width depending on how big an expanse of glazing you are trying to create. Having the opening window does offer the flexibility of opening the window rather than the door to let some air into the room.

Garden Room Bi-fold doors are the most desirable option for a garden room. They are popular because they can be slid to one side, creating a free-flowing connection between the room and the garden.

B-fold doors are a more expensive choice, but if you like the idea of being able to fold a large section of wall to one side, then they are worth the extra cost.

The number of door leaves will depend on the width of your opening. An odd number will give you the option of using one as a main traffic door and function like a regular door.

Garden Room Lintel

Garden Room French doors Can usually be installed without the need for a steel lintel. The span does not usually exceed 1800mm, therefore the timber used for the Garden Room frame can be used and doubled up for extra rigidity.

Garden Room Bi-fold doors require a lintel to be installed above them. The most common size is a 160x80x5mm box section which should be approx 300mm wider on each side.

Garden Room Joist size

The recommended Joist size used for a Garden Room built under permitted development is 4×3″, this allows you to keep the structure height to a minimum by using a 4″ timber whilst maintaining the strength by using a 3″ width.

Garden Room Roof Insulation

Garden Room Warm or Cold roof?

A Cold Roof uses less space, the insulation sits between the rafter, but you MUST have a minimum of 50mm of continuously ventilated airspace above the insulation. This means there need to be soffit vents at each end of the roof.

A Warm Roof is the best option, this is usually a sandwich of 2 sheets of plywood with insulation between which sits above the rafters, the only downside is this makes the roof structure taller and takes the garden room height too high to be built under permitted development.

For more information, see our article: Garden room insulation

Garden Room flat Roof Incline

A flat roof needs an incline of at least 25mm per metre.

Garden Room Rubber Roof

The most common roof used for a Garden Room is a one-piece rubber roof, these can be purchased as a kit containing the rubber, adhesives, gutter trims, and corner pieces, and can be fitted in half a day

Garden Room Flooring

Laminate Flooring is composed of three layers: a plywood or fiberboard base layer, a photo-realistic image layer, and a hard plasticate wear layer to protect against scuffs, dings, and dents. When it comes to hardwood floor alternatives, laminate often looks and feels the most realistic. many laminate products have become virtually indistinguishable from real hardwood in recent years. Laminate is very affordable, When it comes to fake wood flooring, it’s the best of all worlds.

Luxury vinyl floors are composed of rigid or semi-rigid vinyl planks or tiles designed to mimic other types of flooring (wood, most often). They’re almost always sold as click-together flooring products, making them easy to install. And of course, their all-plastic construction makes them highly durable. Ideal for a garden room used all year round.

Linoleum is also incredibly durable and the cheapest of the bunch, it usually comes in one piece which is rolled out like a carpet, it is very quick and easy to install.

For more information, see our article: Which garden room flooring?

garden room interior laminate flooring
garden room interior

Garden Room Insulation

Every part of the frame needs to be insulated:

The walls can be insulated with 100mm Wool insulation rolls to cut costs dramatically.

For more information, see our article: Garden room insulation

Expanding Foam

Expanding foam can be used to fill all of the gaps in your insulation, the fewer gaps you have, the more insulated your garden room will be, Investing in a foam gun gives you more precision and makes the job easier with less waste.

expanding foam can be messy, so mask any doors and windows and wear gloves.

Garden Room Air Flow

It’s important that air can circulate under the floor of your garden office. Particularly with timber floors. If the floor area is not ventilated you are at risk of damp penetrating, and rot or fungal attack. Make sure you have good clearance on all sides for airflow under the structure

Wire Mesh around the perimeter

The gap under the structure could be a great place for animals to live, consider adding wire mesh around the gap to reduce the risk

Garden Room Ventilation

Once you have built your super-insulated garden room you will need to think about ventilation as the moisture will son build up and cause mold.

This can be easily avoided with the use of trickle vents on the windows to create airflow, don’t be tempted to close them, especially if the room is used all day.

If you don’t have trickle vents, consider fitting wall vents, ideally two for good circulation.

3×2 to Catch the Plasterboard

Whilst building the structure you will need to add timber to the corners for the plasterboard to attach to, using 3”x2” which is smaller than the frame will allow you to push insulation behind and fill the gaps you would not be able to normally reach.

OSB sheet size

OSB sheets will normally come in 1220 x 2440 mm sheets, they will need trimming down as the structure will have 400mm centres so the 1220 width will need trimming to 1200 before installation.

Garden room heating

Electric convection heaters are the most common option. They are excellent for garden rooms and offices required for year-round use, as they heat the air quickly and can be free-standing or wall-mounted.  Most are available with 24-hour timers and are thermostatically controlled, some have smart controls which enable you to control them from anywhere, which is ideal to pre-warm an office before your day begins. They are relatively cheap to buy and install.


fast to heat up

cheap to buy


They Create a “dry” air

 Electric oil-filled radiators tend to be free-standing, which offers usage flexibility but they take up floor space. These take longer to heat the room than convection heaters, but the oil retains heat, maintaining warmth for longer after they are switched off, which again can be via a thermostat, timer, or smart controls. They are low in cost with no installation required. 


They create a constant and comfortable temperature

Safety, they are less likely to cause a fire if left unattended

cheap to buy


It can take a while to get a cold room up to temperature

 Electric fan heaters also are free-standing and quite small, they heat up the room really quickly, but the fans can be very noisy. They are cheap to buy with no installation required.


fast to heat up

cheap to buy



Safety, these shouldn’t be left on and unattended

Air conditioning can both heat and cool the air and help maintain a constant temperature and humidity level. It can be a good choice in garden rooms, they can be expensive to install, but cheaper to run than electric radiators.


maintain a regular temperature

cheap to run


Expensive to buy and install

 Wood burners look fantastic in a timber cabin, whether traditional or contemporary, and they perform well too. They warm quickly, retain heat and are carbon-neutral if you can use a sustainable local fuel source. They must be professionally installed by a HETAS engineer to ensure your safety. This can be expensive once you include the flue and installation.


takes time and effort to light each time

cheap to run if you have access to dry logs


Expensive to buy and install

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For more information, see our article: Garden room heating

Garden Room Security Alarm

A garden office can be fitted with a security alarm system that is easy to fit and connect to your smartphone.

Sensors are positioned at key points within the room like windows and doors. If the room is broken into the alarm is triggered.

Don’t forget to insure your garden office and its contents. It’s not safe to assume that your new office will be covered on your existing buildings and contents insurance. It is worth talking to your insurer about your garden room.

Garden Room Internet

Wired internet connections are generally used to establish a wireless network inside our garden room.
The speed provided by ethernet is far greater than a wireless connection. This is particularly true over a larger distance, as wireless drops off in just a small distance

An ethernet connection should take the shortest and straightest path possible. While Cat 6 ethernet cables are rated for up to 100m, this is a maximum connection in ideal conditions. Using a shorter distance means the data does not have to travel as far, reduces failure locations, and lowers latency.

The Exterior Cat 6 cable protects against UV rays from the sun. While Cat5e can be used, Cat 6 can handle gigabit networks better over a long distance due to increased insulation.
This cable can be linked to another router inside the garden room, creating its own wifi hub

Smart Wi-fi Socket

Controlling devices inside your Garden room, like heaters can do done remotely by changing the electrical socket to a smart plug socket, these are available from places like Screwfix and only cost a little more than a standard plug socket.

You can then control your devices from your  phone or voice commands using google or Alexa

Garden Room Lighting

To avoid cutting large holes in the insulation to accommodate down-lights, consider using Low profile down-lights instead.

A dusk til dawn sensor is a great way to keep the exterior automatically lit when it’s dark outside.


Is a garden room a good investment?

The benefits of owning a garden room are truly priceless – it’s not just a good investment, it’s an excellent investment.

There is an initial cost for installation, but you will soon find that it pays itself.


Why are garden rooms so popular?

Many people had to find ways to do the things they loved remotely – meaning there was an urgent requirement for extra space. With a quick turnaround and a far more cost-effective option than building an extension, the garden building was the perfect solution.


Do garden rooms get damp?

If your garden building is airtight and in regualr use, then internal air can create a humid, stuffy space that’s prone to damp and mould. Garden room ventilation is vital in these circumstances.

Trickle vents on the windows will stop this from happening by ventilating the space


Are garden rooms cold in winter?

As long as a Garden room is insulated, it can be heated during winter, just like your home


Do garden rooms depreciate?

As generally speaking buildings do not depreciate in value, provided they are well maintained.


Is a garden room better than a conservatory?

A garden room is a type of practical home extension that provides extra living space, similar to a traditional conservatory. However, a garden room is a much more aesthetically pleasing and modern alternative to a conservatory which has better-regulated temperature and can be used for various functions.

50% Rule

What is the 50% garden rule?

No more than 50% of the area of land around the original house** should be taken up by Summerhouses, Garden Sheds, Garden Rooms, Garden Offices or other buildings.


Do you have to insure a garden room?

Typically, home insurance companies will only cover garden rooms for personal use so if you’re planning to use your garden room for commercial purposes, be that a hair salon or dog groomers, you will need to find a commercial building insurer


Do garden rooms add value?

Floor space is one of the major factors when valuing a property, so it makes sense that the extra space provided by a garden office can add 5-10% to the value of your home. For example, if your home is worth £300,000 then expect an increase of anywhere between £15,000 to £30,000.


Is a garden room cheaper than an extension?

A Garden Room is usually a more affordable option, a garden room is a cost-effective alternative to traditional house extensions.


Where is the best location for a garden room?

Most people prefer their garden room to be in the back garden and unless your property is a listed building, or is situated in a national park or area of outstanding beauty this is permitted… with a few buts! If your garden room is less than 2 metres from any boundary line then the height is restricted to 2.5m.


Do garden rooms need foundations?

The simple answer to this question is yes, they need foundations for stability. Foundations are needed to support a structure by transferring their weight evenly across the ground and helping them to stay strong and sturdy.


How secure are garden rooms?

Most people assume that glazed extensions prove to be attractive targets to potential burglars. On the contrary, if constructed well, then their toughened glazing and strong joinery can make them exceptionally safe and secure.


Can a garden room have a bed in it?

Putting a sofa bed in your garden room so that guests can occasionally stay there is fine and will not require planning permission. But if you want to sleep in it regularly or want to create a self-contained accommodation or granny annex, you must apply for planning permission and meet building regulations.

Garden Room Plans

New and improved !

Digital Plans for various sizes of Garden rooms.

  • Detailed plans
  • List of all materials
  • Material quantity and price
  • Links to each item