Expert opinion, timbers

Should there be uncertainty about the state of the old timbered ceiling (e.g. possible damage), then the old floor superstructure should be removed. In particular at its ends, (where the beams rest on the outer walls), the beams must be checked for any possible  damage to the actual wood.

Depending on the extent of damage found, an expert timber report should be commissioned; this will record the location of any damage and stipulate remedial action.