Building a garden shed

Every garden needs a shed, and so in March 2008 I took a couple of weeks off work to build one. The obvious location is at the far end of the garden, in a corner shaded on both sides by neighbouring gardens’ sheds. There’s room for a reasonable size shed between the fence on one side and my block-built composting area (that is almost as old as the house) on the other.

I contemplated putting in a concrete pad to stand the shed on, but decided this would be too much work and expense, and probably a lot more permanent than is actually required. Instead I settled for timber bearers supported on blocks or slabs, laid on a sand / cement mix as used for paths and patios.

The first picture shows the construction area after clearing the top layer of vegetation and good soil. I was surprised to find an old concrete garden path that I didn’t know I had! Fortunately, this path is right where the shed door was to be. I had hoped that this soil might be firm enough to support the shed, but unlike the previous year, when I took time off to replace my garden fence, March 2008 was rather wet. The ground was so soft that pressing down with my foot would produce visible movement a couple of inches away. I decided to dig down a bit more and lay a sub-base layer. (Removing the path wasn’t necessary as it would be spanned by the timber bearers.)

I bought an 850kg “jumbo bag” of granular sub-base material and spread it in a layer about 1½” thick. (I used small paving slabs as depth markers – you can just about see one or two of them in the picture.) Tamping down the GSB, using a home made tool (a bit of scaffold pole with a lump of wood on the end) brought water to the surface in the wettest corner. The ground there still wasn’t as firm as I’d like, but there was a definite improvement. Meanwhile, the rain eased off to be replaced by snow!

I laid a path of 450mm square slabs along the side of the shed, with a gentle slope following the slope of my garden. This will allow easy access to the side of the shed (eg to apply wood treatment) and discourage weed growth. At the back, where the ground rises to my fence, I laid a line of 440mm x 220mm concrete blocks to form a raised path along the back of the shed. A few more blocks at the left hand side should stop the composter becoming undermined.

After laying the paths I fixed 12 support pads for the shed’s timber bearers. These pads are composed of bricks, paving slabs and/or concrete blocks, as required to build up height and compensate for the gently sloping land. The pads and paths were all bedded on about 2″ of dry sand & cement mix.

The finishing touch was to fill in between the rear blocks and the fence with granular sub-base material, and fill the 2″ gap between side path and fence with concrete. So far this has prevented any weed growth – there were some quite vigorous brambles there before I started.

Before laying the bearers I put some of the excavated soil back to cover the GSB and the sand / cement bedding. This reduced the size of my waste soil heap a bit. The timber bearers are pressure treated to prevent rot, but I decided to lay them on strips of damp proof course as an added precaution. You can see the ends of the DPC strips at the left hand side of the picture.

Finally Sarah and I put up the shed, on a wet and windy Friday. The next morning I fitted the roofing felt, just before the rain began again, and finally installed the window glass. A couple of weeks later I installed guttering and a water butt.

It’s amazing how much soil came out of such a shallow hole.