My stone shed is in need of a refurb. First job on the list is to re-lay the slate roof which is currently leaking. I plan on replacing the battens which are rotten and potentially the rafters as well depending on the state they’re in. I’ll add a breathable membrane at the same time as it currently doesn’t have one.

Being natural stone the internal walls are very uneven. I was thinking of removing the existing rendering, putting battens on the wall, filling the gaps with kingspan and then putting plasterboard over the top. Does this sound reasonable? If so, how thick should the insulation be on the walls and should the inside of the roof be insulated as well?

The shed also suffers from condensation, is it worth adding a couple of air bricks at either end of the shed or some sort of vent in the roof?

my stone shed got a complete workover several years ago – now stores bikes and used as office. Do have some heating but in effect it sounds exactly what you’re planning.

Quite a bit of insulation worked for me, but then it was intended to be habitable (well, usable) rather than just storage so it was worth it. Ground, wall, roofspace insulated.

Stone walls of about 2′ thick..

Air bricks weren’t used. However in office area there is a stove. Bike store area – no vents, no stove, no condensation either (once the leaking Velux had been sorted).

Bump for the afternoon crowd.

Sheep’s wool insulation and Heraklith board to line it, finished off with lime plaster? Would let the walls breathe and keep it toasty.