Roof Furring over Insulation – Screw Requirement questions.
I will be furring over 5″ of rockwool insulation on an unvented cathedral ceiling. Going to use 2x4s and 1x4s ripped from plywood as furring. Attaching the 2x4s vertically and the 1x4s horizontally would give me a larger ventilation channel than doing it the other way round.
Do I install the vertical furring first with my SDWS timber screws? Then attach the horizontal furring to the that with ring shanks or GRKS, etc.
Or, do I have to install the SDWS through both the vertical and horizontal furring?
I’ve attached a drawing that I hope makes sense
The reason I ask; If I can, it’s easier to install all the vertical furring before attaching the horizontal. It would also mean I could use a 8″ SDWS timber screw instead of a 10″ one for code required rafter screw penetration
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
mason,
Definitely do the two layers separately. Both for the reason you cited, but also because it would be an absolute nightmare to try and attach everything at once while keeping everything aligned.