When Pressure Treated Wood Is Required By Code - The Spruce Feb 17, 2017 . House Siding. Shake Siding 1000 x 800. House Shake Siding. Christopher Sessums/Flickr/Creative Commons 2.0. Wood house siding less than 6 inches . Pressure treated wood is required whenever you attach framing lumber (as shown here) or furring strips to concrete or other exterior masonry walls..