Does anyone know how to calculate suitable board thickness for joists at 1000mm centres? I have some stones with a roof in France I want to board out, and the joists are approx 220mm x 150mm at 1000mm centres. Currently the rotten boards look like waney edge oak boards, around
30mm thick, but too soft now to know if that was ever a good idea.I'm assuming ply would be the best material, assuming eventually I'll want to lay some smarter looking regular floor boards on these.
Thanks.