In Britain, when a house is re-thatched, it is traditional for the thatcher to strip off only as much old thatch necessary to reach a sound base coat on to which the new thatch can be fixed. This is known as 'sparcoating' or 'overcoating'. When water reed is used, the old thatch is completely removed, right down to the roof timbers, Water reed is also an ideal material for newly constructed housing or barns, However combed wheat reed should not be ruled out on new builds.
There are exceptional cases where stripping back to the roof timbers may be unavoidable, perhaps because the thatch has been badly neglected or the timber structure has suffered failure. If you have a listed building and stripping to reveal the timber structure is recommended by your thatcher, you will require advice from the local conservation officer, we at Stuart Viggers are happy to do this on your behalf.