Free DIY Summerhouse Plans

Choosing the right summerhouse style

The three styles below each suit different gardens. The choice usually comes down to where in the garden the summerhouse will sit, and what view you want from inside.

A traditional summerhouse is rectangular with a pitched roof, double doors at the front and large windows either side of the door. It is the easiest of the three styles to build, fits naturally against a fence or hedge, and works in almost any garden.

A corner summerhouse uses an L-shaped or pentagonal footprint to fit into the corner where two fences meet. The angled front faces out into the garden, giving a wide view from inside without taking up usable lawn. Corner summerhouses are the most space-efficient choice for smaller gardens.

An octagonal summerhouse is an eight-sided design with a pointed roof. It is the most striking of the three and gives almost 360-degree views from inside, which makes it a good choice as a feature piece in the middle of a larger garden. The build is more involved than a rectangular summerhouse because of the 22.5-degree mitre cuts on the wall plates and roof segments, but our plans give every angle and length so the cuts are straightforward.

Where to put your summerhouse

Position has more effect on how much you actually use a summerhouse than any other design choice. The two big things to think about are sun and view.

For sun, work out where your garden gets the late afternoon and early evening light - that is when you are most likely to use the summerhouse - and put the doors and main glazing facing in that direction. A summerhouse that catches the evening sun gets used far more often than one that sits in shadow by 4pm.

For view, face the doors away from the back of the house and across the longest sight line in the garden. Looking down the length of a garden from a summerhouse at the far end is one of the most relaxing views in any back garden, and the trick costs nothing in the design.

If neither perfect sun nor perfect view is available, prioritise sun.

Glazing, doors and ventilation

Summerhouses live and die by their glazing. Most of our plans use double doors at the front (typically 1500-1800mm wide as a pair) and full-height side windows either side. The doors open outward so the internal floor space stays clear when they are propped open on a hot afternoon.

Single-glazed Georgian-bar windows are the traditional look and are cheap, but they do nothing for thermal performance. Double-glazed sealed units cost more up front but make the building usable for longer in the spring and autumn shoulder months, and they cut condensation on cold mornings. Most builders pick double-glazed for a summerhouse they want to spend real time in, and single-glazed for a purely-summer occasional-use building.

Even with the doors open, a summerhouse with a south-facing wall of glass can become uncomfortably hot by mid-afternoon. The plans include trickle vents on the windows and either gable vents or a low-and-high passive vent pair to keep air moving. A small ceiling fan is a cheap add-on that makes a big difference on the hottest days.

Foundations for a summerhouse

Summerhouses are light enough that they do not need a slab foundation in most cases. The three options that cover almost every garden are:

• Concrete pad piers - small (300x300mm) concrete pads dug below frost level, with a treated timber bearer running across the top. Cheap, quick and the kindest option for the lawn underneath.
• Ground screws - galvanised steel screws driven into the ground with a hand tool or a small machine. Very fast to install, no concrete, and easy to remove later if the summerhouse is moved.
• A full concrete slab - the most permanent and most expensive option. Worth it on heavier builds (octagonal summerhouses, anything 12x12 or bigger) and on sloping ground.

The plans include foundation suggestions for each design and size. As long as the foundation is level and the bearers are pressure-treated, the summerhouse itself will sit happily on top for decades.

Insulating a summerhouse for shoulder-season use

A standard summerhouse is uninsulated, which is fine for May to September but cold from October onwards. If you want to use the building in spring and autumn as well, light insulation in the roof and walls makes a big difference for relatively little money.

50mm of mineral wool or PIR between the roof rafters takes the chill off in March and stops the building overheating in July. The same insulation in the walls keeps the temperature stable through the day. A small electric heater (an oil-filled radiator on a timer or a low-output infrared panel) then makes the building usable on bright but cold winter mornings.

If you want full year-round use - working from home, a quiet room for hobbies, a garden gym - a fully insulated garden room is a better starting point than an upgraded summerhouse. The construction is similar, but the wall, floor and roof build-ups are designed for it from the start.