… construction material, requirements for attic space?…
Consider the following: Do you need to replace the roof?
The answer may be a resounding and obvious YES – you may have holes as large as tiles or a ridge line like a camels back. But there are more subtle reasons to replace a roof. To conform with insulation and ventilation related building reg’s, to get the attic space you need or to accommodate the solar or PV panels you intend to deploy, it may be easier, quicker and cheaper to replace, rather than fix up the existing roof.
Keep an open mind.
Protect your heritage
One aspect of the roof that I would retain where possible are the original roofing materials. The welsh slates I’ve kept are far superior in terms of durability and appearance to the more cost effective modern materials I would have likely had to use if an entirely new roof had been required.