Simple Green Roof Play House Extension

This project has been on my mind for a while and this year I finally went ahead and made it. The plans have changed multiple times but ended up being really basic and straight forward. This means it could be put up in a day or two.

To be clear: this project is about the roof extension to our existing garden shed and not about the shed itself. The part that is covered in this instructable can be seen in the schemes attached to this step.

I have provided the measurements I used for this project, in milimeters, simply because that's what I needed for my situation. Of course a project like this will be different for everyone, which is why I will not focus too much on the measurements and more on the process.

Along with the play house I added a terrace floor and path to our garden which I will include in this instructable.

Even though the final result is a very basic roof structure, it provides the children a dry and shaded play area which can change function along with their imagination. I hope you'll enjoy reading my building process.

Tools:
- shovel
- ground drill
- saw
- drill
- spirit level
- tape measure
- pencil
- wire
- sticks

Hardware:
- screws (different sizes)
- nails
- steel brackets

Materials:
- wooden posts, about 3x3"
- wooden beams, about 2x3"
- wooden planks/siding, about 0.5x8"
- tar (if you use soft wood for the posts)
- sedum trays for the green roof

Optional:
- sand
- gravel
- terrace tiles
- curbstone beams or blocks
- anti root cloth
- interior decoration (lights etc)

Our starting point is shown in the first picture above. Because the white gravel got dirty we decided to use that elsewhere and replace it with a darker gravel for the path and terrace tiles inside the play house. I removed all the gravel and washed it clean (this may have been the most time consuming part of the whole build).

Next I layed out the plans for the house and path with a wire and some sticks to make sure I didn't remove too much grass. The wire also helps to keep the curbstones level in a later step.

I based the dimensions for the house on the amount of space available and a combination of the terrace tiles and sedum roof trays that would both fit into the same area. I ended up making the house about 4ft x 5ft.

I removed quite a bit of earth to make space for the sand and gavel. Be sure to keep some of the removed earth in case you get too enthousiastic (as I was) and might need to put some back later on.

Once the area is cleared of grass and your play house dimensions are layed out, the next step is to place the posts in the ground. This can be done several ways, including concrete or steel foundations, but I chose to use only wood instead.

If you use hardwood for the posts they can be placed in the ground without treatment. Softwood however will need to be treated to prevent rotting when exposed to wet ground for long periods. I used a black tar for this, which needs to be applied to a little above the ground level.

To secure the posts firmly in the ground the rule of thumb is to put about a third (1/3) of the posts into the ground. I wanted the lower part of the roof to be about 1,3m or a little over 4ft above the ground, so I put them around 0,6m or about 2ft into the ground.

To create the hole for the posts to sit in, I used a ground drill. This way you don't need to dig a huge hole and fill it up again. Make sure the hole is a little deeper than you need. Put a bit of your 'levelling sand' into the hole so you can stamp it down with the post and create a steady base for your post and not have it push down into the ground when you put the roof on.

Use the spirit level constantly when putting in the posts to make sure they are level and straight. I kept measuring the distance between the posts and used the curbstones to keep the posts in place a bit.

Once the posts are in the right place and are straight you can fill the hole with sand until it is packed tight. Poor some water over it so the sand can settle and keep adding sand until the hole is filled up and the posts are secure.

The next thing to do is to mark the posts at the correct height so they can be cut off in order to place the beams. Mark one of the posts at the correct height and use a beam together with a spirit level to mark the same height on the second post. This is a more accurate way then measuring from the ground, since the ground can vary in height. If you have a level terrace or curbstone in place, you can measure from there of course.

When the posts are marked they can be cut off. It can be a tricky angle to saw, but try to keep the cut as level as possible.

The next step is to place the beams and connect the posts to your existing construction. There are many different ways to do this. I chose to use the same wood I used for the posts as the main beam because the dimensions are the same which makes for an easy fit. So both my posts and main beam are about 3x3inch.

I simply placed the main beam on top of the posts and pre-drilled before screwing them into the posts. I used only 1 large screw in each post since the weight of the roof will be pressing down and the beams connecting the shed will prevent it from rotating. If you really want to be extra safe you can use 2 screws.

For the three secondary beams connecting to my shed I used slightly thinner beams, around 2x3inch. You want to place these so that the cross section is in 'portrait' orientation to get the best structural quality.

I chose to use wooden blocks cut at an angle to attach and support the beams. I used some spare pieces of beam and cut these at a 10 degree angle to make 5 identical blocks.

Another option is to use steel corners or brackets to attach the beams to the posts, but the brackets I found were very heavy duty and difficult to bend at an angle. I made a sketch of both options.

I calculated the height for the beams to correspond with a 10 degree angle from the top of the posts to our shed and marked out where they needed to go on the shed. I checked my measurements by using a beam and spirit level to make sure all the blocks were at the same height.

You will need at least 2 screws for each block and they need to be long enough to go through the blocks and into the load bearing post behind it. Pre-drill the wood before screwing to prevent splitting the wood with the thicker screws.

Once the blocks are in place you can place the beams on top, pre-drill and screw them into place. Again, use large enough screws to go through the beam and into the blocks to properly secure them. Whenever I'm in doubt about the length of the screws I need I simply ask the hardware store employees which ones to use. This saves me a lot of time searching through hundreds of different types and sizes.

To connect the middle beam to the main beam you need to use a steel bracket or shoe since there is no post to connect a block to. I bought a steel shoe that fit my beam perfectly and that could be attached on both sides (see image). To attach this shoe you will need smaller screws that go about half way into your beams. Use at least 2 for each side, so 8 in total (or more). Smaller screws can be used without pre-drilling, but I always do just to be safe and not split the wood. When using hardwood you definately want to pre-drill the holes otherwise your screw will break.

Once all the beams are in place you can put the roof planks on. Because my play house is not meant to be completely waterproof and it will have a sedum roof that retains water, I used cheaper straight planks to make up the roof. If you want a steaper roof that is more waterproof you can use siding with grooves that can be overlapped to make sure water will run down and not go through the cracks.

I put the planks on top of the beams and marked them where they needed to be sawn off. I started at the top against the shed and worked my way down to the posts. The roof planks can be attached to the beams with 2 nails at each beam, so 6 in total for each plank. If your planks are warped or bent you can use screws instead to keep them in place.

A small detour from the play house itself, but an important part to make it look and feel like a real house. I decided to make a path from our terrace to the house and put some wooden terrace tiles from Ikea inside the house to give it a nice cozy feeling.

I used concrete curbstones to create the borders between the path, the house and the garden. This comes down to digging a trench and filling it in with earth and pushing and wobbling the curbstone until its at the right depth. Use the string mentioned earlier to make sure the different curbstones will line up with eachother and are either level or at a slight angle that follows the slope of your garden. When the curbstones are in the right place, fill in the gaps with earth and sand to secure them firmly.

After removing the ground to about 4 inches deep I used levelling sand to create a level and smooth surface. I used the spirit level itself or a piece of leftover beam to scrape the sand and level it out across the entire area.

On top of the sand I placed some anti root cloth to prevent weeds coming through later on. On top of that I put the terrace tiles inside the play house and the gravel on the path.

To give the play house a nice look and create some more green in our garden I placed ready-made sedum trays on top of the roof. These trays come in different types, either with plastic trays or eco-friendly foam. I chose the foam trays for our house. They can be put right next to eachother which creates a single green slab once it starts to grow.

I put a piece of anti root cloth on top of the roof underneath the sedum trays to prevent roots coming down the ceiling of the play house. I slid the trays on the roof and packed them together tightly.

After this I put some planks around the roof to keep the sedum in place and create a nice finish. I held the planks in place and marked them to be cut off. Once cut I held the planks in place and screwed them onto the beams. To be safe you can pre-drill the holes, specially when screwing right at the edge of the planks. Another option is to use nails if your wood is nice and straight.

On the inside of the siding I screwed in a small steel corner to make sure the corners would be flush. I should have done the same against the shed, since the planks have warped a bit since its been finished.

And then all that is left is to enjoy your nice, green roofed play house! It not only looks nice, but it provides a dry place to play during the rain and a shaded place to pay when its very sunny.

I put up some solar led lights inside so its lit up at night which adds another dimension to the garden. We fixed a chalkboard to the shed which makes for a nice school classroom or a window with a view.

The plan is to add some more finishes to the house, like a fence and window sills to put stuff on. But for now, the kids like playing in their new house the way it is :)

I hope you enjoyed this instructable and I'd like to hear your comments or suggestions.