Horizontal exterior sidings like wood clapboards, vinyl, and
fiber cement have traditionally been nailed directly to the
underlying sheathing, typically over a water-resistant
underlayment of asphalt felt or some sort of housewrap. That’s
still common practice, but over the past few decades, a more
labor-intensive technique known as rain-screen siding has been
steadily gaining ground. Reportedly first recommended by
Canada’s National Research Council in the early 1960s, the rain-
screen approach involves fastening the siding to vertical
furring strips, which are usually spaced to correspond with the
wall studs. The resulting vertical channels are usually covered
with insect screening at top and bottom but are otherwise left
open to permit free passage of air. As in a conventional siding
application, the OSB or plywood beneath should first be covered
with a properly flashed and lapped layer of felt or housewrap.
Draining and drying. According to rain-screen advocates, the
open channels tend to reduce wind press