The black weatherboards can become cracked and warped by the sun.
The original plans (see the plans page) specify boards 7″ wide by 1″ thick. They were either rough-sawn or rough-planed so it is important to replace with a board that is not smooth. We have found that gravel boards from fencing suppliers produce a good result, with the added benefit that they are treated with preservative at the factory. The sizes available do vary from time to time, but Timberstore at the M40 junction often have 200mm x 22mm x 4.8m (cost about £20 in 2025) and these can be cut down to match our original boards.
It is best to paint the boards before installation. Use black Solignum Architectural – this is a breathable stain, not a paint. Once installed it will be necessary to paint over any visible screw heads etc.
The visible boards are nailed to an inner layer of narrower vertical boards which are in turn nailed through a layer of bitumen felt into the lightweight concrete blocks behind. Both the boards and the blocks have become brittle with time so nailing into old materials is not recommended. Screws and wall-plugs would be better.
If you need to replace a lot of boards you might consider doing a whole face and installing insulation behind it. We have detailed plans for doing this as it was done at #2 in 2020.