04 Mar 2015

Building your own garden room


Nick Green, author of the Self Build Garden Room Guide, shares his top tips for building your own garden room.


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Over the last 15 years garden rooms have become a popular way of extending your home. Most garden rooms are bought for use as home offices or studios, but we are seeing more and more complex designs being built for permanent living.

Often referred to as ‘posh sheds’, garden rooms are actually built like modern timber frame houses using the same materials and building techniques – as far from a garden shed as it is possible to get! These buildings are highly insulated meaning they are suitable for use all year round.

A garden room makes a great self-build project. There are two common routes for the self-builder – buy a kit and assemble it yourself or design and build the garden room yourself from scratch.

Buying a self-build kit is the simplest route and companies like Building With Boxes offer high spec solutions which include a Structural Insulated Panel (SIP) core, cedar cladding, aluminum clad doors, electrics and more. This type of kit is delivered to you with assembly instructions. With prices starting at £4625 plus VAT this can be a quick and cost effective way of self-building a garden room.

The downside to buying a garden room kit is that you have little flexibility over the design of the building. If you have a specific design in mind it’s not too challenging to design and build a garden room from scratch.

Your own design

When designing a garden room you need to bear in mind the Permitted Development rules for Outbuildings. In many cases, a garden room can be built without the need for full Planning Permission, as long as the positioning and dimensions comply with Permitted Development. Flat roof garden rooms under 2.5m high are very popular as they can be sited close to the boundaries of the garden. With pitched roof designs you will need to site the building at least 2m from each boundary.

If you plan to sleep in your garden room, even only occasionally, it will need to comply with Building Regulations. Otherwise, garden rooms up to 30m2 can be built without Building Regulations as long as it is either 1m from the boundary or built from substantially non-combustible materials. Of course, all electrics and plumbing in the building must fully comply.

The Planning and Building Regulation rules will have an effect on your design and choice of materials.

Key elements

A concrete slab used to be the foundation of choice for a garden room, but today plinth foundations such as Jack Pads or Swift Plinths have revolutionised the market. These adjustable pads are quick to install – needing very little site preparation – and overcome any unevenness of site. These foundation systems are also very popular because they are made from recycled materials and can be cleanly removed from the site should the building ever be taken down. Core structure

Garden room suppliers either favour a traditional timber frame for the core of the building or Structural Insulated Panels (SIPs). As a self-builder you have these options open to you too. The traditional timber frame is what most self-builders tend to favour, but you do have the option of working with a SIPs manufacturer who will precision cut the SIPs to your plans including door and window openings. Exterior

As with any timber frame building it is important that a breather membrane is present in the build up. Over this, garden rooms tend to be timber clad. Western Red Cedar is by far the most popular option for both its durability and aesthetic appeal. Larch, Thermowood and manmade boards like Cedral are also popular options. Roof

By far the most common roof covering for flat roof garden rooms is EPDM and you can buy kits for garden room size buildings online. Insulated roof panels which form both the interior and exterior finish and the external finish are popular with some designers. When it comes to pitched roof designs the entry level option is Asphalt shingles. Cedar shingles create a beautiful finish; you also have the option of slates or tiles, but you will need to design your roof accordingly to take the additional weight. Doors & windows

The doors and windows are often one of the main design features in a garden room. It’s common practice to use house quality doors and windows in garden room designs, whether they be UPVC or Aluminum clad. It is fashionable to have large expanses of floor to ceiling glazing. Bi-fold doors which fold back to open up the whole wall are a must have feature with buyers.


This is where garden rooms tend to vary. Basic models are lined with MDF or vinyl coated boards. Higher spec buildings have fully plastered interiors which have the feel of a room in a house. Birch plywood linings are also popular, offering a modern pared down style. When it comes to the flooring, laminate or engineered flooring are the most popular options, but you could also fit carpet or rubber.


The electrical system is the one job that you need to call in the professionals for. Like with any building project there is both a first and second fix phase. The garden room normally has its own consumer unit which is connected to the house’s mains supply via an armoured cable buried under ground. An earth rod is also fitted. With garden rooms often being used as home offices, it’s a good idea to incorporate data, telephone and audio visual cabling into the system. Trunking for these cables is normally buried in the same trench as the electrics.


As discussed at the start of this article, more and more garden rooms are being used as living annexes. Toilets or full shower rooms are designed in creating a truly self-contained building. You may need to call in advice on this aspect of the design and build as work will need to comply with Building Regulations and you will have to give thought to the sewage connections and water supply.

Designing and building a garden room is an enjoyable project and definitely within the scope of a competent DIY-er. By designing and building a garden room yourself you will not only get a building tailored to your needs and tastes but it will be the fraction of the cost of buying one on a full installation basis. However, if this isn't an option, then there are many garden room companies to choose from who offer a diverse range at varied prices.

Further information....

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