New slate roof. A few questions still.

[buttwhy]

Hi there all on DIY Dr. I'm a long time reader but first time poster today.

I'm considering replacing a very old slate roof in Scotland with a new slate roof. The house is a one and half storey solid granite walled with a warm room in a roof design. I have 2 questions I cannt find the answer too.
1) Currently my roof has solid 18mm boarding to which the slates are directly nailed to. When I replace these there will be a breathable waterproof membrane then slates but should I use battens aswell ,and if so what are the benefits, or nail them direct to the boards.
2) If you start slating from the bottom working up how do you avoid breaking the slates you've just laid as you get higher. A roof ladder would be uncomfortable to work off all day.

PS under the roof boarding/sarking there will be foiled solid insulation with a 50mm gap.
All help appreciated.

[stoneyboy]

buttwhy,
If you nail direct onto the roof boards you may go through the board completely.
Breathable membrane manufacturers specify that you should counter batten and then batten and ventilate the gap formed.
When laying the slates stagger your laying so you can always double nail every slate.
end

[buttwhy]

Thanks for your answer. The recommended battens for the tiles are 25x50 but should the counter battons be 50x50 or 25x50?

[stoneyboy]

buttwhy,
Provided you are fixing the counter battens into the rafters use 25x50.
end

[TheDoctor4]

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