External timber cladding

[mal62]

I want to fix softwood timber shiplap cladding to the outside of my chalet and need info about how i fix it at the corners of the building and around the windows for a neat finish any help would be greatly appreciated.

 

[big-all]

assuming 12mm finnished thickness
2x1" sawn treated screwed to the corner with 1" overhanging the edge mirrored at each end

 

[mal62]

Thanks-the finished thickness however will be more because i want to put insulation boards between the battens because it was sodding freezing last winter owing to the walls only being static caravan thickness.i'm thinking about 35mm insulation and 35mm battens.