Installing Standing Seam Metal Roof

A standing seam roof is constructed from many interlocking panels that run vertically from the ridge to the eave of the roof. Standing seam roofing is suitable for either spanning across purlins on typical spacing, or laid directly over rigid insulation and/or solid decking.

Metal roofs are becoming more popular due to their long life expectancy. However, you’d better be ready for the cost of this roofing material if you decide to use it. These roofing systems can cost anywhere from 3 to 5 times more expensive than asphalt shingles. Although comparable in cost to most high-end roofing materials, such as cedar shingles or tile, it will outlast any other roofing system on the market.

The most common metal roof are what are known as “standing seam.” This name refers to the fact that the roofing panels are made with “ribs” that stick up. The seams between panels are hidden in these ribs, raising them above the path of water shedding off of your roof.

Before You Begin:

Be sure to have a solid underlayment, with a vapor barrier covering it, before installing your metal roofing. If you are re-roofing your home, you’ll want to remove the old shingles, so that you can have a smooth surface under the metal roof. If there is any water damage to your roof sheathing, repair it before installing the metal roof.

How to Install it:

Start by attaching the drip edge to all eaves (horizontal roof edges), whether you are installing gutters or not. Some people say that the drip edge should be installed under the roof sheathing, but its primary purpose is to protect the edge of the sheathing from water damage. So, you are better off installing it above the sheathing. Screw it down, tight to the roof, every 8” to 12”. When you reach the end of one piece, overlap the next by at least 2”. Be sure to open the lip of the overlapping piece slightly to insure a tight fit.

If you are building a hip roof, you’ll need to install the drip edge all the way around the house. At the corners, overlap the two ends, cutting a “tab” in them, so that the overlap is not visible from the ground.

Installing the first roof panel is the most critical. You want to be sure to line it up exactly perpendicular to your roof ridge. If your roof isn’t exactly square, you may not be able to use the edge of your roof as a starting point. If your first panel needs to be cut in order to make it fit for either vents or the roof being out of square, be sure to leave an extra 1” of material, to bend up the edge of the roofing, simulating the joining rib. You will need this rib for the installation of your gable trim.

You will notice that the two edges of the panel aren’t the same. One will have a single lip sticking up and the other will have a folded over lip. The folded over lip is designed to overlap the single lip, and lock onto it. So, when installing your roof panels, you want to lay them in a direction that allows you to put the single lip side towards where the next panel will be installed over it.

You will need to cut and bend two hooks at the bottom end of each roofing panel. The first hook runs the width of the panel, less the standing ribs. This should be 7/8” wide and folded under. It will hook onto the drip edge when you install the panel. The second “hook” will be the piece of the sings standing rib that is left where you’ve cut for the drip edge hook. Leave it there, as it can be folded over the locking seam, as an extra security for the end of the seam.

When you place your first panel on the roof, slide it up, to engage the drip edge hook onto the drip edge. Hold the panel in place with 1 screw, through the center of the panel, 1” from the top edge. This is the only screw that you want to put through the surface of the panel, as to avoid causing a place for leaks to form. The screw at the top will be covered by the ridge cap.

Attach the clips to the standing single edge of the roof panel about every 10” to 12”. To avoid buckling the panel, only screw the clips at the outer set of holes (the ones farther from the panel). If you live in a high wind area, you may want to install the clips every 6” to 8”.

Once the first panel is in place, the second panel attaches to it. Place the doubled over standing rib lock over the single rib lock on the first panel. Hammer it down with a rubber mallet to cause the rib to lock. Once you have the lock action started, you can push the panel up to engage the drip edge. Attach this panel in the same way as you did the first; continuing with each successive panel, until you reach the end of the roof.

All gable ends should have an extra 1” of material sticking over the edge of the roof. Bend this up, vertically at 90 degrees. Your gable trim will hook over this fake standing rib. Simply hook the gable trim over this fake standing rib and attach it to the fascia board of your gable end with matching colored screws that have rubber gaskets.

The roof cap consists of 3 pieces; two “Z” channels and the cap itself. The Z-channels need to be cut to the appropriate length to fit between the standing ribs on the roof panels. They should fit closely, but not tightly, so you can make them about 1/4” shorter than the space between the ribs.

Cut a short piece of roof cap to use as a gauge in installing these Z-channels. Since the roof cap has locks to hook onto the channels, you want to space them so that those locks will engage when the cap is pressed onto the channels. Attach the channels to the roof with 3 screws for each section, sealing the channels to the roof with a quality sealant. Pay particular attention to the ends of the channels, where they butt up to the standing rib.

Although the cap itself snaps onto the Z-channels, glue it as well with the same sealant you use for the Z-channels, to insure long life, without blowing off. For multiple sections of roof cap, you’ll need to cut the locks off 3” of the underside of one piece of cap, in order to allow it to overlap the adjacent piece of cap.

What You Need to Know About the Building Code:

The manufacturers of these roofing systems have made them to be compliant with the building code. As long as you follow the manufacturer’s suggestions, your roof will be compliant.

Tricks & Tips:

Metal roofs are installed with screws. So, if you don’t have an electric screw gun, you might really want to consider buying one. While an electric drill will work, the difference is that a screw gun is designed to shut off when the screws are at exactly the right depth.

Drip edges come in different sizes, specifically the “face” side (that’s the side that hangs vertically over the roof sheathing), which can be anywhere from 1-1/8” to 2-1/8”. Your supplier will probably supply you with whatever is their “standard” size if you don’t specify. If you need a particular size, or have a maximum width that will work, be sure to specify that to the supplier.

You want to avoid having any vents or other penetrations of the roof come up through the locking rib, where the panels come together. To avoid this, lay out your roof, measuring the distance of each of these from the starting edge. Ideally, you want all penetrations of your roof panels to happen in the middle of the panels.

Whatever you do, don’t try and install your roofing on a windy day. The sail area of these panels and their light weight make them fly out of your hands and off your roof very easily. The worst part is that they usually get damaged when this happens.