My Site, My Stuff

Workshop Extension

Early 2017 and my home engineering business was outgrowing the double-garage, more space was needed.

The design

After some measuring, it looked like a 10×8 shed could be added to the end of the concrete slab Compton garage, using the existing up-and-over door area for the connection. It was designed in CAD and built as a self-assembly kit style project – this makes things so much easier to build. I did this project at the same time as the small garden shed (here) to save delivery costs etc.

The build

The extension is built on the existing concrete apron, this is solid and gently sloping away from the door as expected. As the floor would have pretty good support, I decided to us the same 2×3 treated timbers as the rest of the build. Spacers were used get levels and on the last steep part of the slope, the timbers were cut. DPC membrane was place below the timbers.

Planning floor supports
Side view of floor supports

The floor is 20mm marine grade plywood, this was also used for the roof. The floor was fixed before any other parts were made, there is a small 20mm transition step between the wood and concrete but this helped by the water-stop ridge in the concrete at the threshold, in use the step was never noticed.

The floor laid and fixed

The join to the concrete slab build was a tricky one – there were no flat surfaces, the end of the garage was not vertical, the original wood apex fascia was rotten as well.

Awkward joint
Underside view of the top panel join
The inside of the rotten apex cladding, this was replaced with marine ply


A side panel under construction

The far-end wall was built in-situ and not as a self-assembly part, this was done to ease construction and to take up any small irregularity in in the walls/floor.

Walls and roof fitted, end wall being built
Two of the grandkids found it most fun and helped out

A small UPVC window was fitted in the far end of the side wall – this was to aid ventilation in summer, give a little daylight and also to give a quick means of escape if needed.

Front wall up and roof supports going in
Double doors were fitted to the rest of the opening area

The roof was covered in heavy-duty EPDM rubber sheet, glued down. The rubber was taken up the apex fascia and then clad in tongue and groove for appearance.

Roof laid
The finished build


The extension proved very successful in use, it housed my powder-coating oven and general parts storage. The garage access was useless as a real garage simply because the house to house distance meant a car would never fit! The previous owners just managed to get a tiny MGB classic in there by hand pushing it, carefully. I have kept the original double door and all its fittings so if future owners want to return it they can.


Its now late 2021 and the business was recently closed after 12 years of trade, it was very successful and served its purpose. The garage is now our games room and the extension is a tool store area for the usual DIY clutter.