Introduction: Build a Garden Room

About: I am an engineer / designer interested in many subjects. When not making things, I enjoy mountain biking, canoeing and camping.

We had an unused corner of the garden where the old play area was, which my children had grown out of.

I researched Garden Rooms and decided to build one for myself.

I planned it to be a Man Cave but it has been taken over by the family as a Gym!

See my Pinterest board here for more ideas;

I had some lengths of timber left over from a previous roofing project

It took a few weekends to build, here is how I did it...


4" Foam insulation under the floor

Assorted 3x2 and 6x2 pine timber for the frame - already owned

Plywood for the roof and floor

Western Red Cedar Cladding for front facing walls

Box Profile Polyester Coated Steel Sheet 0.5mm Thick for the rear facing walls

4 Oak framed double glazed doors - Secondhand off Ebay

Rubber Sheet Kit for roof

Rough sawn old pine boards for internal cladding - already owned

Fibreglass Loft insulation for insulation in the walls and ceiling

Laminate flooring

Black Plastic Decking for the step

Assorted electrical sockets, switches, down-lights and wire

Step 1: Step 1 : Prepare the Plot

The plot was cleared and levelled with sand.

I used old decking to frame the sand.

The shape of the room was determined by the fence, lawn and a large tree.

The sand was tamped down by foot to compress it.

I then laid 4" Building Foam Insulation on the sand.

This was then covered in 5mm plywood to protect it.

This method of construction has low enviromental impact as no digging or concrete is used.

Step 2: Step 2: Build the Frame

I built the wall frames on the ground using 3"x2" timber and wood screws.

They were then lifted up to the vertical and fastened together

I added a thicker beam over the doorway to take the roof beams

The 6"x2" roof beams were added, I ensured that there was a slight slope backwards to drain surface water

You can see a difference in height between photo 3 and 4, I decided that the room looked too high with the roof beams on top of the doorway beam, so I moved them to hang behind the beam on joist hangers

The grey sheet in the last photo is just a temporary tarpaulin

Step 3: Step 3: Fit the Doors

I bought the doors off Ebay, they were new and still boxed but not ideal as they were replacement doors for a bifold system that I did not have the track or frame for.

I bought a bottom running door track, most bifold tracks are top hung.

I had to make the frame and fit the track system to the doors. This was the trickiest part of the build and could be simplified if you bought a door set with frame and track included.

The design was made more complex as I decided to add interest by having one of the doors as a fixed pane around the side and a solid panel to the left of the doors.

I also wrapped the frame in a breathable membrane cloth that I had left over from my roofing project.

Step 4: Step 4: Clad the Frame

Western Red Cedar Cladding was fixed to the front facing walls with stainless steel wood screws hidden in the tongues. The cladding needs to reach the roof at the top and go down past the foam at the bottom but not touch the soil

Box Profile Polyester Coated Steel Sheet 0.5mm Thick was screwed on the rear facing walls with 38mm Wood Tec screws. These screws drill their own hole in the steel and then screw into the wooden frame. I used the driver shown in a battery drill to put them in. This is low maintainence and cheaper than the cedar but not as attractive, which is why I only used it on the sides facing the fence.

The joins between the steel cladding and the cedar cladding were covered by 90degree steel capping, that matched the steel sheets. It went over the steel sheets and under the cedar cladding.

Step 5: Step 5: Cover the Roof With Rubber Sheeting and Coat the Wood

I purchased a rubber flat roof kit which included a single rubber sheet, adhesive and trim and nails.

The rubber sheet is glued down to the plywood roof, it is then trimmed to size and the edge capping is nailed on.

The kit only came with 90deg corner pieces so I bought a few extra and cut and glued them for the other angles.

I coated the cedar siding with Osmo UV Protection Oil (Clear Satin) and the Oak Door Frames with Sadolin One Coat High Performance Wood Stain (Natural) to prevent water and UV damage.

I added guttering to rear edge where the rain water ran off. This was taken away to a soakaway.

The room was now waterproof

Step 6: Step 6: Adding the Decking Step

The decking step serves two purposes, it aids entry and exit but also covers the area below the windows.

I made up a frame using 4"x2" and secured black plastic decking to it, to match the black trim on the roof.

I also added an outside light.

We started using the room at this point,even though the inside was not fitted out.

Step 7: Step 7: Interior Fit Out

First I added laminate flooring

I then added fibrglass loft insulation into the walls and ceiling voids

I then clad the walls and ceiling with the rough sawn timber.

This wood was actually the flooring in the loft of our house, which I removed when I added thicker insulation and plywood loft flooring on stilts. The wood needed jet washing to remove the dirt and grime.

I fastened it on the walls in a diagonal fashion, partly for aesthetics but also to brace the rectangular frames.

I added a fuse box and lighting and power circuits

For lighting I inserted downlights into the ceiling as the ceiling is low

Step 8: Conclusion

We are very happy with the Garden Room

It was originally intended to be a Man Cave but has become the Family Gym!

We keep the exercise equipment in there and I have put a CD player and flat screen DVD player on the wall for aerobic sessions.

For relatively little cost we have turned an unused corner of the garden into a useful space that is regularly used by all members of the family.