OSB or Ply for flat roof

[padstar]

Construction will be joists/18mm deck/130mm PIR/18mm Deck all fixed through to the joists at each layer.

Spoke to the roofer and he said he can do a single ply rubber roof as long as there is limited traffic up there. I only plan to be up there 1 time a year for maintenance so is this the better option?

 

[oldbutnotdead]

Construction will be joists/18mm deck/130mm PIR/18mm Deck all fixed through to the joists at each layer.

Spoke to the roofer and he said he can do a single ply rubber roof as long as there is limited traffic up there. I only plan to be up there 1 time a year for maintenance so is this the better option?

Yeah I'd go with it, your proposed insulation is the setup where many GRP roof owners have had noise problems.