Cladding and Attachment
Furring strips are required for most cladding attachment when exterior rigid foam is ≥2” thick. Furring strips can be ¾” thick, but some cladding requires 1.5” nail embedment, so 2x4s should be used. Predrilling the ends can prevent the furring strips from splitting. When working around windows, transitions, or other commonly trimmed out areas, the furring strip width should be increased to provide adequate nailing area for trim and cladding.
At a minimum, furring fasteners should be installed through the foam and into studs. Depending on the cladding installation requirements and stud spacing, additional furring strips might be required intermittently between studs.
Furring strips effectively create a rainscreen which increases the durability of the wall assembly. The rainscreen allows any bulk water such as wind driven rain to drain, the cladding to easily dry out, and prevents solar driven moisture from entering the wall assembly.
Without a rainscreen water can be driven into the wall cavity or cause cladding failure due to moisture absorption. When the cladding can’t dry out, finishes can start bubbling and peeling and the cladding itself can start softening and rotting.
Heavier weight claddings such as thin brick/stone veneers will, at a minimum, require larger fasteners with closer spacing, and sometimes standoffs must be used. Building Science Corp provides nice guidance on this, but approval by a structural engineer may be required. Very heavy weight claddings such as full brick or stone will likely require a brick ledge or similar base support (typical brick ledge designs create significant thermal bridges and thermally broken strategies must be implemented).
Cladding attachment options
Insulation thickness implications
Impact of wood blocking vs z-girts vs fiberglass clips... etc, vs. true continuous insulation