re-slating an old Scottish roof

I've got an old (1890's) slate roof in Scotland.
typical construction - Scots slate, on sarking boards on rafters - insulation at ceiling level. No eaves or ridge ventilation - plenty of vent through the slates and boards.
BUT- nail sickness abounds, and i'm spending a fortune every spring having it patched up.
So, i'm biting the bullet and having it re-slated.

I will be stripping the slate, putting a breather membrane on the sarking, and then re-slating (with new slate). Plain and simple.

QUESTION:
If i put a breather membrane in, can i still avoid venting the roof?
There are no eaves to speak of in a traditional Scottish roof, and i want to avoid vent slates at all costs - hideous.
If it is fine, and a breather membrane and open jointed sarking will do the job, what membrane should i be using?

Thanks in advance!

 

I had my roof done and was advised that although the membrane was breathable, it will not offer anywhere near the same kind of ventilation as the roof was used to, thus, roof vents are the only safe option.

My understanding is that the internal roof environment is used to having the amount of air movement it currently gets. Lowering that amount may, or may not, cause an issue. I wouldn't want to find out afterwards that it had!

I tend to think of the breather membrane a little like Gore Text. I have GoreTex boots and my feet still get sweaty, even though they are meant to be breathable. My feet don't get sweaty in sandals (although I wouldn't wear them!)

 

thanks.
What membrane did you use, out of interest?

 

I think it was Tyvek or something like that. I didn't do it, it was done by a roofing firm a few years ago.

 

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