How Is a Standing Seam Metal Roof Installed?

What are the main steps in installing standing seam?

Installing standing seam follows a set order: inspect and prepare the deck, lay the ice barrier and underlayment, install the edge trim, set and fasten the panels, close the seams, and flash every penetration, wall and ridge. Each layer depends on the one beneath it being right. Before material is ordered, the roof is measured and the panel layout planned so seams line up sensibly with ridges, hips and features such as dormers and chimneys. Panel lengths come from those measurements, and long panels often run in a single piece from eave to ridge. Once work starts, crews protect landscaping, siding and windows, set up fall protection, and work in sections so the house is not left open to weather. On older New England houses the deck often needs some repair once the old roof is off, which can add time.

Can standing seam go over existing shingles?

Sometimes, but standing seam is fussier about what is underneath than most roofs, so a tear-off is often the better route. The flat pans show bumps and ridges in the surface below, which can make waviness, called oil canning, more visible. Cedar shingles, shakes, natural slate and concrete tile must always come off. A single layer of asphalt shingles may stay in place only if an inspection finds the roof suitable. Multiple asphalt layers, soft or rotted sheathing and sagging areas all point to a tear-off. Tear-off also lets the crew see the deck, replace damaged boards, correct ventilation and install ice barrier directly at the eaves. On many older New England homes, especially those with plank sheathing, that inspection turns up repairs that are better made now than after the new roof is on. Local codes also limit how many roof layers are allowed.

What goes under a standing seam roof?

Under a standing seam roof is a solid deck, an ice barrier along the eaves and other vulnerable areas, and an underlayment across the rest of the roof. Metal roofs can get hot in summer sun, so high-temperature underlayments are commonly used beneath them. The ice barrier, a self-adhering membrane, is especially important in New England. Codes based on the International Residential Code call for it at the eaves in areas with a history of ice forming there, and it is often extended into valleys and around chimneys and skylights. It does not prevent ice dams, which come from heat loss and ventilation, but it adds protection if meltwater backs up. Ventilation belongs in the same conversation. Balanced intake at the soffits and exhaust at the ridge helps keep the roof deck cold and dry, which works on the causes of ice damming and attic condensation.

How are standing seam panels attached and joined?

Standing seam panels are attached with fasteners hidden under the seams, using either separate clips or a nail strip formed into the panel edge, and then joined by snapping or folding the seams closed. No fasteners go through the flat face of the panel. Clips are fastened to the deck at set spacing along each panel edge, and each new panel's seam covers the clips of the one before. Floating clips let panels slide as they expand and contract, which matters with aluminum and with New England's wide temperature range. Nail-strip panels are fastened through slotted holes along the edge and suit shorter runs. Snap-lock panels close by pressing the seam together by hand; mechanically seamed panels are folded once or twice with a seaming tool. Clip spacing and fastener type come from the manufacturer's specification and often tighten near eaves, rakes and ridges, where wind loads are highest.

How are flashing and trim handled?

Flashing and trim are handled with custom-bent metal pieces at every edge and penetration, and this is where most of the skill in a standing seam roof shows. Eave trim, rake trim, valley pans, sidewall and headwall flashing, chimney flashing and the ridge cap all have to shed water while letting the panels underneath move. Pipes and vents get boots or custom flashing, and larger features such as chimneys and skylights often need a cricket on the uphill side so water and snow do not pile up behind them. On older New England homes with big center chimneys, that detail matters. The ridge is closed with a vented or non-vented cap, depending on the ventilation plan. Closures under the cap and at the eaves keep out wind-driven rain, snow and insects. A good installer bends trim to fit your roof rather than forcing generic pieces into place.

Where do snow guards fit in?

Snow guards, or snow retention, fit in as a design decision made before installation, for the parts of the roof above walkways, entries, decks, driveways, lower roofs and gutters. Standing seam sheds snow readily, and a full roof of heavy wet snow sliding at once can damage what is below or injure someone. Placement depends on roof pitch, panel length, the snow typical where you live and what sits under each eave. Many standing seam snow retention systems clamp onto the seams so they do not puncture the panels. Discuss snow retention during your in-home roof consultation so it is part of the plan rather than an afterthought, and make sure your contract states whether it is included and where it goes. Not every eave needs it; a roof that drops snow onto open lawn may be fine without it.

Step by step

1. Inspect the roof and plan the panel layout.
2. Tear off or prepare the existing roof and repair the deck.
3. Install ice barrier and underlayment.
4. Fit eave, rake and valley trim.
5. Set and fasten panels, then close the seams.
6. Flash penetrations and walls, and cap the ridge.
7. Clean up and do a final walkthrough.

Common questions