Best way to attach pressure treated wood to painted siding ?
I live in the damp Pacific Northwest. Going to put in a breezeway roof of corrugated polycarbonate between 2 garages, span of 6 1/2 feet. Old structures with redwood shiplap siding. My friend who makes his living remodeling says to use pressure treated 2x4's as framework, but not to screw them directly onto the siding, as i was assuming to do. He suggests using short cedar shims between lumber and siding at the screw sites--for air and water circulation and to keep crud from accumulating and prevent rot. Also to level out the vertical slant of siding. I'm hesitant about the flimsiness of the shims. Is there a different or better way of attachment? And is pressure treat a given?
Pressure treated is not a given unless you know the wood will be exposed to the weather. If its under the new rood and will remain dry, use regular framing lumber. If it will be exposed, use treated lumber but use composite shims. They're available at every big home store here in the East, I'm sure you can find them at a store near you.