Nailed ridge boards, with diagonally set ridges.

These are introduced once the cost of nails falls with the introduction of cut nails. A cut nail is rectangular in cross section and is rapidly cut from a sheet of iron, with little hand finishing. Now looking on the internet you will see a date of 1790 for the introduction of cut nails, and further refinement in 1830. Whilst machines may have been patented, by Americans, at this time, cut nails are somewhat older. Christopher Polhem, a prolific Swedish engineer built a nail cutting machine in the early 1700’s.

The earliest I have found is at Pertwood Barn, just over the border in Wiltshire. The barn has extensive nailed construction details. Dating from the earliest graffiti, 1769, which fits with the historical evidence. There are two types of nailed ridge detail on site, possibly indication this was an early adoption of the nailed ridge board and the best detail had not been established. What is common to all the ridges is they simply butt up to the principal rafters, there is no ridge cut out, the ridge board is all that supports the ridge. This simplifies assembly as the ridge simply drops in from above and can be secured with a nail.

At Pertwood one ridge detail has the ridge half lapped and it sits on a flat topped ridge board. Supporting in this way could not be recommended as it may lead to sheering and splitting of the ridge. The other detail has the ridge board with a V shaped notch to support the ridge. As the ridge has it’s bottom faces supported there is less risk of sheering. This stronger V detail is what is adopted in later years.

Manor Farm at Stourton Caundle is a later build. Exact dating is difficult but a suggested date of around 1800 would be close. The construction uses the later post 1790 cut nails. Here we have the V notch ridge boards.
At the same farm is a fine barn, part true cruck, part jointed. This also has a nailed ridge board. Clearly the barn is several hundred years older than the nailed ridge board detail. It is clearly part of a later roof repairs.