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How to build a summer house or garden room
Building a summer house or garden room isn’t easy. As well as the physical demands of building it, you’ll need to consider planning permission and foundations before your new space can take shape.
Read on for advice from people who have completed a DIY summer house or garden room themselves.
Unsure what type of summer house or garden room would be best for you? Read our guide on how to buy the best garden room
Before you start building a summer house or garden room
Many summer houses and garden rooms can be bought in pieces for you to construct yourself. Instructions should be provided, although you'll need basic tools to complete the job.
These will probably include a handsaw, screwdriver, mallet, hammer, spirit level, tape measure, drill and ladder – but check the instructions or ask the company you buy it from to make sure you have everything you need before you start.
If you’re planning to build from a kit, also check the following:
- Are all the fixings (screws, nails, etc.) included?
- Is the wood pre-cut and planed, or will you need to do this yourself?
- What is the construction method (for example tongue and groove)?
- Are electrics and lights included (if you plan to have these)?
- Are full instructions provided?
- Are the parts labelled (so it’s clear what is what)?
- How many people are required for assembly?
DIY summer house tips
If you’re more confident with DIY, you might decide to build your summer house or garden room from scratch, rather than buying a kit to assemble.
Which? members we surveyed* who have done this shared the following tips:
- 'Get the best roof possible even if you need to source it from another supplier.'
- 'Ensure the doors and windows are weathertight, foundations are level and gutters are fitted. Electrical installation should be incorporated in the design otherwise all the cables will end up being on external / surface conduits.'
- 'With DIY installation ensure the roof is fully secured to the walls and doors are well-fitted. High winds lifted my roof off and it was heavy – it needed two people to lift one side so that the roof could be disassembled for reinstall.'
Building your own garden room or summer house means you won't need to pay for installation, but think carefully whether you are confident that you can complete the job.
One Which? member wishes they had used a professional installer:
Get it installed professionally - we managed a DIY job but some of the pieces were very heavy, and the extra cost would have been worth it to avoid injury, and get it done and finished quickly.
If you have no experience with assembly or construction work, it’s worth hiring a professional carpenter or builder.
Use Which? Trusted Traders to find a reliable trader near you:
How long does it take to build a summer house or garden room?
As a rough guide, professional installation can take between one and five days, depending on the size and complexity of the structure.
Summer houses are generally simpler, and can be built in one to three days. But garden rooms are sturdier, more complex structures and building one yourself will take several days. As an example, a small 4.5 x 2.5 metre garden office with a flat roof, 25mm insulation, double-glazed windows and sliding door would take approximately four to five days, according to the manufacturer’s estimate.
These times are based on two adults and don’t include fitting lighting, plumbing, heating or internal decoration. The exact time it will take you depends on the season and weather you’re working in, the type of foundations you choose, your DIY skills, and whether you have any help.
With either option, you’ll need to factor in time for the foundations or a base, if this isn’t part of the agreed installation.
Foundations for garden rooms and offices
Garden buildings need a solid, level base to sit on. If you’re hiring installers to assemble yours, they may request that this is ready before they will deliver it. Some specify the type of base they require, for example paving slabs or concrete, and may even send you a plan for the base when you have ordered your room.
Don’t skimp on foundations if you want your structure to last – they support the structure of the building. Good foundations are particularly important if you plan to put heavy items in your garden building, such as gym equipment, a snooker table or hot tub.
One garden room owner told us:
Invest in a professionally laid base – it makes the erection of the building much easier, makes it stable, and a flat base will reduce the chances of leaks etc. which could result from an uneven base.
Subsidence is a risk if your foundations are poor or you omit them altogether, warns Gareth Jones, managing director of UK Leisure Living, a Which? Trusted Trader that focuses on foundations for garden rooms.
Concrete foundations are the traditional approach to creating a sturdy base for your new structure. This typically involves digging a trench and filling it with concrete.
Ground screws are a newer option for foundations, Jones explains. Large screws (up to 2.5 metres long) are driven into the ground to support the structure above. You can move ground screws if you decide to relocate your garden room in future.
They can also be installed without heavy equipment – getting cement mixers or diggers into your garden to build concrete foundations can be a challenge if your home has limited access.
It’s important to take into account the type of soil that the foundations will sit on, to make sure that it can take the weight of the foundations and building, and to factor in how it reacts when it’s very wet. Speak to a structural engineer or building control for advice on what your garden room will need.
Looking after your summer house or garden room
Check the maintenance instructions when you buy your garden building, so you know what you’ll need to do to keep it in good shape for many years to come. Many rooms are guaranteed for 10 years or more, and some Which? members have owned summer houses for much longer.
Wooden buildings can come pre-treated, or you may need to treat them yourself with paint or preservative when you first assemble them. They also typically need re-treating, sometimes as often as every year. This is important to maintain the weatherproofing, structure and look of your garden room.
Wooden buildings can shift and settle over time. After the first few weeks, you may need to re-adjust the doors or windows if they have started to rub or stick. Wood can sometimes warp if exposed to the sun or moisture for a long time, especially if the wood isn't treated. Wood will also change colour as it weathers.
If you want a specialist to treat your wooden outbuilding or to preserve the structure's timber, check out Which? Trusted Traders to find reliable traders in your area.
Garden room guarantees
Garden rooms come with different lengths of guarantee, including five and 10 years. Check what it covers – for example, whether the structure of the building is covered – and what rights you have if there’s a problem with it in future.
Find out what you need to do for the guarantee to remain valid. Some guarantees specify essential maintenance, such as treating the wood.
Also remember to keep your proof of purchase and any other documents you’ll need for the guarantee.
Our garden room research
*In September 2020 we surveyed 11,539 Which? members about garden rooms, including 1,264 people who own one.