Build a Garden Room




About: I enjoy making and building things. Most of this is improvements to my house and cars but sometimes I get to build something more interesting.

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

I researched Garden Rooms and decided to build one myself.

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 celing

Laminate flooring

Black Plastic Decking for the step

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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.

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.

Step 5: Step 5: Cover the Roof With Rubber Sheeting

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 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 2"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 celing voids

I then clad the walls and ceiling with 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

Step 8: Conclusion

We are very happy with the Garden Room

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

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

For relativeley little cost we have turned an unused corner of the garden into a useful space.

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    17 Discussions


    22 days ago

    Did you cant the roof so water would run off?
    Awesome build. How much did the materials cost you? Like the idea of using it as your own private gym.
    Used to be if you lived in the county (which I do, instead inside of any town's limits) you could pretty much do as you pleased. Not anymore. Unfortunately, the county I live in in East Tennessee has now got an ordinance that any additions need to have a permit to build and be inspected after build, which, of course, means they charge you $$$ for the permission to build. Sigh. :(

    2 replies

    Reply 22 days ago

    Yes the roof slopes front to back to shed the water.
    As for costs, I don’t keep receipts but roughly £200 for the dense foam insulation, £100 for timber (I already had a lot of the timber), £200 for the plywood, £100 for the doors, £300 for the door track, £200 for the door frame, £800 for the Cedar cladding, £300 for the steel cladding, £400 for the rubber roof. £100 for the fibreglass insulation, £100 for the step decking. £100 for the lighting and sockets.
    That gives a total of around £3,000, which is cheaper than they cost to buy, circa £12,000!


    Reply 21 days ago

    So about $3,700 US money. You're right. Would be cheaper doing it yourself than having someone else build it. Thanks!


    23 days ago

    One niggle on an otherwise great, sensible project. From what I can see of the power sockets, you are in the UK. The cabling should run vertically to the sockets, not horizontally. Doesn't seem much, but sometime in the future someone will drill the wall in a safe place - only it won't be.

    1 reply

    Reply 22 days ago

    You make a good point - the cables should run vertically to the sockets.


    22 days ago

    I really didn't need another backyard project, but this looks amazing. It looks like you were able to use a lot of materials that you already owned. I'm going to look at my budget. Thanks for the informative build!


    22 days ago

    Great instructable! How much space between the back wall and the fence? Was it difficult to fix the cladding on the back wall due to limited space? I am planning on building a garden room in a corner of my garden too and am concerned about access to the back during the build

    2 replies

    Reply 22 days ago

    Hi, I left 1 foot (30cm) between the frame and the fence posts. It was tight but feasible and I am quite large! Use a battery drill or 90 degree driver in a larger drill to drive the screws in. The tighter you make it the less space you loose.


    22 days ago

    Since you did not mention preservative treatment for the wood, I assume there is none. You may find that problematic as the wood close to the ground absorbs termites and other insects.

    It is 4m across the back and 4m front to back.
    This was the size rubber sheet that I ordered.
    The floor area is not 16m as it’s not square.

    Elaina M

    24 days ago

    This is awesome !!! Well planned and documented - you've got my backyard reno wheels spinning ! I've got the perfect neglected corner that could totally use a Garden room! Thanks for sharing your build !!

    3 replies
    definingsoundElaina M

    Reply 23 days ago

    What climate region do you live in? Can you estimate the total building area?

    My municipality requires a permit for any structure greater than 108 square feet.


    Reply 22 days ago

    Hi, we are in the UK, here Garden Buildings are considered Permitted Development and do NOT require planning permission as long as: The building is placed less than 2.0m from the boundary of the property with a maximum overall height of no more than 2.5m from existing ground level. That is why most have flat roofs.
    The area of our room is about 10 square metres. (90 square feet)

    sherwood01384Elaina M

    Reply 24 days ago

    Many thanks for your comments. The room has been very well received by the family.