I’ve recently did an inspection in Pasadena C.A. and been doing a lot of research on the roof for my client, This is what was observed, Gypsum board sheathing was installed at the base with “NO wood sheathing over the gypsum board” then a felt membrane installed, then the wood or fire treated cedar or wood shake surfaces. It appears that the roof system inspected was missing " the wood sheathing" although a permissible method as long as it is fire treated and would be considered a class B rating.
Well this is the latest information I have found. It turns out that a roofing company obtained a permit to re-do the roof. The permit states that they were going to install 1/2 gypsum board then the cedar shakes, which is exactly what they did and no indication if it was treated or not with fire retardant. I understand that this would be considered a substandard system now because of 1) No confirmed retardant treatment and 2) Now that moss is on it, any preservative treatment is not permissible :roll:…
Note as per (FEMA libary) that when shingles or shakes are fire-retardant-treated, they cannot be impregnated with preservative treatment,
prudent action for client
before end of inspection option would be for their insurer to evaluate and approve or disapprove roof system compliance
the standard as far back as i can recall for assembly protection was/is 5/8" Type X gypsum board
there may be other state or local info i’m not aware of
if you don’t exclude insurability in your pia
consult your attorney and add this or similar
**The inspection does NOT imply insurability or warrantability of the structure or its components. **
Wood shingles (not shakes) should be installed on spaced sheathing to improve it’s drying ability. Installation on a solid deck without mesh or some other method for allowing airflow beneath the shingles is bad.