Replies

1. 
   Malcolm_Taylor | Sep 06, 2021 04:47pm | #1

   Scott,

   Furring strips are sufficient, although depending on the exposure on your shingles you may find that they end up being so close together that the result is an almost solid substrate, and you might as well have used plywood.

   I don't know much about how near shingles do in your climate. Here in the PNW you are lucky to get 20 years out of them. and that might be worth considering when deciding which substrate will make replacement easier when it (all to soon) comes around.

2. 
   scottgazelle | Sep 07, 2021 08:22am | #2

   Thanks Malcom - if using plywood, would you worry about trapping moisture in the Rockwool? Though tedious to install, I was thinking that furring strips would lead to a more breathable exterior.

1. 
   Malcolm_Taylor | Sep 25, 2021 07:40pm | #5

   Scott,

   I don't know enough about it to comment usefully. I suspect the plywood is more than permeable enough to keep the Rockwool dry. The moisture problems with cedar shingles I've had to concern myself with here are keeping en0ugh air-flow around them to stop rot.

3. 
   Jon_R | Sep 07, 2021 09:49am | #3

   The above sheathing Rockwool is the only insulation or there is other insulation below the sheathing?

   Possibly applicable: IRC 806.5 says: "Where wood shingles or shakes are used, a minimum 1/4-inch (6.4 mm) vented airspace separates the shingles or shakes and the roofing underlayment above the structural sheathing."

1. 
   scottgazelle | Sep 25, 2021 04:43pm | #4

   sorry for the delay - there will be insulation below the sheathing too - probably a combination of spray foam and Rockwool batts