Think of vinyl siding as more of a weather screen than a
weather barrier. Wind-driven rain will make its way behind this
screen. In new work, it's important that you carefully apply
housewrap or felt paper before installing the siding. Make sure
all seams are overlapped and taped, and that door and window
openings are detailed properly (see "Making Walls Watertight,"
When an older home is being resided, the vinyl is often
installed over the existing siding. In these situations, it's
important to "tighten up" the original siding. This usually
involves fastening loose boards and recaulking around windows,
doors, and other penetrations. Cosmetics aren't important
— the goal is to provide a second line of defense for any
moisture that finds its way past the vinyl siding.
Fascia and Soffits
It's a good idea to complete the soffit and fascia work before
installing the siding. Soffit material may be either vinyl or
aluminum, but for fascia I prefer aluminum coil stock. It's
thinner than vinyl, so joints are less apparent, and it can
also be site-formed for a variety of eaves conditions.
Never use nails to fasten fascia. Instead, snap the fascia
over the F-channel at the bottom of the subfascia and insert
the top in a strip of vinyl utility trim under the roof
drip-edge (Figure 2).
Aluminum Soffit & Fascia Details
The author prefers
aluminum fascia, because it can be site-bent to trim out
different rake and soffit configurations. Although small pieces
of aluminum (such as the corner insert or the triangular return
piece) may be nailed tight, the long lengths of fascia are held
in place with trim strips or nails in slotted holes, which
allow for movement.
The fascia material will be held firmly in place, but will
still be able to expand and contract.
Punch locking tabs in the top edge of preformed fascia with
a snap-lock punch (Figure 3).
Figure 3.Specialty tools
are required for a quality vinyl job. Use a snap-lock punch to
make tabs in the top edge of preformed metal fascia (left).
These tabs prevent the fascia from pulling out of the utility
trim without restricting movement. A slot punch (right) makes
the elongated nail holes that allow for movement under a nail
These tabs prevent the fascia from pulling out of the
utility trim without restricting movement caused by changes in
temperature. Fascia that is formed on site from thinner coil
stock should have a continuous locking hem formed on the top
The lower edge of rake fascia should be fastened to the
subfascia with aluminum trim nails driven through slot-punched
holes. These slots permit the fascia to expand without
Many installers mistakenly "turn the corner" by bending the
fascia material at a 90-degree angle. Instead, stop fascia runs
at inside and outside corners, and tuck a corner insert behind
the fascia at these points. The insert provides a "background
cover" that prevents the wooden subfascia from showing at the