11 degree roof pitch

For the amount of work involved and cost I would just have a torch on felt roof... If you wanted a slate roof you should had gone with the recommended pitch of 15 degrees minimal, any lower and you have to be creative and do what everyone else says above and even then you still can’t guarantee a little leak or two... You basically got a flat roof all be it a steep flat roof but a flat roof never the less. Regards Frankie BT Roofing Services

For a low pitch roof roof that has to be covered with tiles or slate we would board the roof with 18mm osb, 2”x2” counter batten the rafters then torch on felt over the board and counter batten, double felt and batten over that, so even if the water does get through the slate and felt it lands on the torch on felt and runs off.

you would need to lay the 18mm osb down and torch felt onto that. after that you need to counter batten the roof with a treated timber double felt, batten then slate from there

Needs to be counter battened and felted 1st