A reader's Roofs and roofing question: Shingle to metal roof?

Kyle V.   from   Kingston, Canada   had this Shingle to metal roof question.

I am preparing to convert my roof from shingle to metal roof. What i am wondering is, does there need to be a sheathing on first of can i run it just on batton on the trusses? Or does it require OSB?

Bill's answer

Hi Kyle, The normal layout for a metal roof is trusses, battens, and an insulation foil or blanket, then the metal sheeting.
No OSB sheeting needed.

If there is sheeting already on that is in good condition then I don't see any reason to remove it though. Provided that the battens are screwed through the sheeting and into roof trusses. But still use insulation foil in between though.

There couple of issues maybe.
If sheeting was on originally then it would in part have been acting as stiffening or bracing for the roof surface. So if you removed this stiffening from the roof, Then you should replace it in some way.
Thisis easy to do by way of fixing diagonal flat strap braces. Cheap and simple.

Your existing battens may be closer together than necessary, this is no problem really, except that they may be thinner than recommended.
You may for example have to remove every second 2 x 1 1/2 batten and replace with it with a 3 x 2 to fix the metal roofing to.

The company supplying the metal roofing will have detail sheets for fixings, supports, etc.
Good luck with it
Cheers