Oriented Strand Board (OSB)
Can you install cedar shakes over OSB?
Certi-label shakes and shingles have only been tested on plywood decking. Make sure you use a very good quality hot dipped galvanized or stainless nails that are ring shanked to hold the roof to the OSB and check with your local Building Official to see if this type of application is permitted.
Can OSB be used on walls under cedar sidewall?
Check with your local Building Official for requirements in your area.