Vinyl siding

Vinyl is hung, not nailed. Almost every failure starts there

Vinyl siding performs well for a long time when it is installed the way it is designed to work: hanging loosely from its nail hem, locked course to course, and free to grow and shrink across its length. The three most common installation errors all take that freedom away.

How it is supposed to go on

1. Nails centered in the slot, driven into solid framing or sheathing, and left loose enough that the panel can slide sideways by hand. A long panel moves measurably between a winter night and a summer afternoon.
2. Panels locked fully into the course below along their whole length, not just at the ends.
3. Gaps left at trim and corners so an expanding panel has somewhere to go rather than buckling.
4. J-channel and trim flashed into the water barrier, not caulked to it. Trim is not waterproofing.
5. Clearance at roofs, decks and grade, so the bottom edge is not sitting in water or snow.

How it fails in a wind event

This market records damaging wind far more often than hail, and vinyl is one of the first things on a house to show it. Wind pressure lifts the bottom edge of a course, unlocks it from the one below, and then works along the run. The panel often ends up on the ground two streets away, and the ones still on the wall next to it are frequently unlocked without looking damaged at all.

• Missing panels, usually starting at a corner, a gable end or the windward elevation.
• Unlocked courses that rattle and can be lifted by hand. This is the damage that gets missed, because from the street the wall looks intact.
• Torn nail hems, where a panel pulled against its fasteners and the hem gave way. It cannot be re-hung on a torn hem.
• Cracks radiating from a fastener, which is the signature of a panel that was pinned and then loaded.

Cold, impact and the January problem

Vinyl is noticeably more brittle at low temperature. A ladder knock, a stone from a mower, or hail that would simply bounce in summer can split a panel cleanly in a hard freeze. It is also why repairs in deep winter need care: unlocking a cold panel to replace its neighbor is a good way to crack two more.

Two problems people are surprised by

Melting and warping near reflections

Certain energy-efficient window glazing can concentrate reflected sunlight onto a neighboring wall strongly enough to distort vinyl. The distortion is localized, follows the sun, and is not an installation defect.

Heat sources too close

Grills and fire pits against a vinyl wall cause exactly what you would expect. It is worth knowing before rather than after.

What to ask for on a vinyl job

• What happens to the existing wall: is the old siding coming off, and will the sheathing and barrier be seen?
• Whether the water-resistive barrier is being replaced or repaired, and how it is lapped at openings.
• How windows, doors and roof-to-wall junctions are being flashed — specifically whether kick-outs are going in.
• Fastener spacing, which is what stands between the wall and the next straight-line wind event.