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Behind-the-Scenes Protection

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," 12/95). 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

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Figure 2.

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).

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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 head. 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 edge. 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 buckling. 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 joint.