Scottish roof construction

[Luxmore100]

Hi, any help would be appreciated, I have just bought an old croft house in the highlands of Scotland. The roof is fibre cement slates nailed directly onto sarking boards with a breathable membrane between, ie no batons . I am going to replace the slates as they have become discoloured. My question is, is the above method ok or would it be better to cross baton first and then nail the slates to them. All the slates are coming off, so it would be better to do the job right. Many thanks for any advice.

 

[Alastairreid]

Originally the croft would have been roofed with horsehair felt and scotch slates, ballachulish or similar.
These would have been nailed hard to the sarkin board with verges bedded in lime mortar.
The slates were head and shoulder nailed on every course due to the high exposure in the highlands.

Fibre cement slate look pretty but imo are not man enough to sustain the extremes of weather which you are subjected to in that part of the country.

If you decide to use battens then it will also have to be counterbattened which will result in the roof covering sitting approx 50mm from the sarkin with the verges, valleys etc being deeper and more exposed.


If it was my roof i would be sourcing scotch slate and replacing with them using traditional methods.