Installation Guide

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Snap Loc / Standing Seam Panels

Marco Metals standing seam panels come in a variety of profiles and finishes to meet most needs for residential and commercial roofing. Our most common panel, a snaplock, screw-flange panel, is ideal for residential and commercial applications where panel lengths do not exceed 40 feet and water flow is adequate to keep rainwater depth below ¾”. Our clip-system panel is designed to allow for thermal movement of longer panels and the higher underlap rib will accommodate heavier rainflow. The mechanical seam panel works well for a tighter lock and a slimmer rib profile but requires expensive equipment to properly install. All standing seam panels are available with a flat pan or with striations or pencil ribs for increased strength and less oil canning. Both panels and trim are fabricated using state-of-the-art computerized equipment at our facility in Harrisonburg, Virginia to assure uniformity and consistency. We also offer jobsite fabrication for longer panels or complicated projects. Panels are roll-formed to the lengths specified by customers in either Acrylic-coated Galvalume® or any of our fifteen colors of Kynar® painted Galvalume® in 26-gauge and 24-gauge high-tensile metal. We can also meet your 22-gauge and .032 or .040 Aluminum needs with reasonable minimums. Your Marco Metals dealer will be happy to assist you in making the best choice for your particular roofing needs.

Marco Metals standing seam panels are fabricated from AZ-50 (painted) or AZ-55 (Acrylic-coated) Galvalume ® grade 80 coil stock. The Acrylic finish is not only durable and cost effective, but also offers valuable reflectivity as well. The paint system used on painted products offers optimum exterior protection and superior resistance to corrosion and ultraviolet radiation while reflecting significant amounts of heat away from the building. Acrylic coated Galvalume® carries a 20-year limited finish warranty, while our Kynar® painted metal carries a 40-year warranty. Marco Metals stocks a complete line of fasteners, sealants, tools, pipe boots, and other accessories to meet the needs of the metal roofing contractor. A complete line of in-stock flashings and trims are available in all colors. We will also fabricate whatever custom trims you may need to complete your project.




Pencil Rib

Material Handling

Be careful when handling metal panels and trim. Edges are sharp and proper safety equipment should be worn to prevent injury. Forklifts can damage the underside and edges of panels so extreme caution is necessary when using such equipment. Do not drag panels off the stack to remove; either lift or “roll” the panels off. Panels should be carried vertically by the panel edge. Panels over 20’ long may require extra help to handle. Long panels can also be lifted with a forklift if lift straps are used to “roll” the panel or a spreader bar is used.

Material Storage

Paint and finishes of Marco Metals panels and trim are designed to withstand severe rain and wet weather conditions. Neither paint, galvanized, nor Galvalume® finishes, however, are designed to be in continuous contact with water for long periods of time. Irreparable damage will result if uninstalled panels or trim are allowed to remain wet in storage. Be sure to store material that will not be installed immediately in a dry location. Wet material should be airdried and re-stacked if installation is not planned right away. DO NOT cover metal panels with plastic or tarps without leaving adequate ventilation (at least 12 inches) under the cover and metal stack. Neglecting this will result in significant collection of moisture between panels and void the paint warranty.

Trimming and Cutting Steel Panels

Trimming and Cutting Steel Panels The best device for cutting steel panels across the profile is a good-quality offset hand snips, a nibbler or a power shear. Use of circular or reciprocating saws to cut metal panels is not recommended and will void the paint warranty. If you do use a saw, cut with the bottom side up to prevent hot shavings from contacting the painted side. Be sure other panels are protected from hot shavings. To cut panels lengthwise: Note Carefully where the panel is to be cut, and using a straight-edge, score deeply down the length of the panel with a sharp-pointed utility knife. Folding the panel along the score mark, and bending back again if necessary, should produce a clean break in the panel. Snips or shears may also be used. Cutting holes in the metal panel is done by drilling a starter hole big enough to accommodate the cutting tool to be used. Pre-drilling metal panels before installation is a common practice, but doing so while in the stack can result in burrs that leave scratches in the painted surface of the panel below. Should such scratches be exposed and rust they are not covered by the paint warranty. Metal filings from cutting or the installation of screws, if left on the panel, can cause rust spots to form. Care should be taken to brush all such particles from the roof surface after installation to maintain paint integrity. CAUTION! - Clean all metal shavings and particles off the roof to avoid unsightly rust stains.


Roof Pitch

Marco Metals roofing panels require adequate pitch to ensure proper water drainage. Use of these panels on pitches lower than 3/12 are not recommended. It is important to remember that metal will not leak. Leaks happen at ends, sides and penetrations of metal panels. Metal roof panels are designed to shed water, not contain it. Flashing and installation must be designed with that principle in mind. Our 1 ¾” rib, clipped panel will give the best protection if extra run-off accumulation is expected because of the pitch of the roof or the length of the panel.

Roof Preparation

Oil-canning is a wave-like, rippled appearance extending up the length of a metal roof panel after it has been installed on the roof. Some oil-canning is common with any metal roof but careful storage, handling and roof preparation will keep it to a minimum. Any irregularities in the roof, including uneven plywood joints, warped plywood, uneven trusses, poor application of underlayment, the use of button caps with underlayment, etc., can promote oil-canning or dimpling. Careless storage and handling can also contribute to oil-canning. Care should be taken to provide a flat, uniform surface on which to attach the panels. Striations or pencil-ribs may be added to the panel to minimize oil canning. Alternatively, 3/8” backer rod may be taped to the back center of a flat panel for the same purpose. Oil canning is normal and is not cause for rejection. Synthetic underlayment should be used over solid decking rather than tar paper. Button cap nails will show through the metal and should be avoided in favor of staples for fastening underlayment. Standing seam panels should not be installed directly over shingles unless purlins are used over the shingles. Screws must be long enough to penetrate completely through the metal, shingles and the roof deck. They should be fastened according to the appropriate building code. Battens must be installed to support the entire width and length of ridge, eave, hip, valley, and gable-end trims. Standing Seam 21 For solid decking, at least 15/32” structural plywood or 5/8” OSB supported on rafters at a maximum of 24” on center is required.

WARNING! - Direct contact between any lumber
pressure treated with copper, and standing seam panels must
be avoided in order to prevent potential corrosion.

Roof Application

Panel installation should begin at the gable end of the roof opposite the prevailing rain-bearing wind (this will provide added assurance against wind-driven rain being forced under the laps). Measure one panel width in from the roof edge. At this point chalk a line from ridge to eave. Place the leading edge of the first panel along this line. It is extremely important that this panel be laid square to the eave and ridge so that the remaining panels will line up square on the roof frame. It is wise to have a person at the eave and at the ridge to ensure that the proper panel coverage is being maintained across the roof. Also be sure that the panels are properly side-lapped and snapped down. It is recommended that the eave end of the panel be hemmed around the drip edge. The open panel ribs at the eave can be sealed with caulk or trimmed to provide a cover flap.


Since standing seam panels are usually installed over solid decking, any ventilation issues arise from improper construction or installation and are not caused by the metal roofing itself. The temperature differences between shingle roofs and metal ones may require that ventilation will have to work differently and must be taken into account.


1” flat-head screws are the most common method used for installing screw-flange panels or panel clips. Screw and clip spacing must be done according to local wind codes. Most areas require a screw or clip at the eave and another 1’ above that, with the same at the ridge. 14” to 24” spacing should be adequate for the rest of the panel depending on the wind load. For screw-flange panels it is important that screws be placed in the center of the slot and not overtightened. To allow for thermal movement the panel should only be fastened tightly at one end. Usually that is at the ridge since fastening z-bar there pins the panel tightly. Color-matched pop rivets are used to fasten trims together. Remember that each pop rivet has a hole in the center and should be placed so that water dripping through will fall onto the roof pan. Pop rivets should be installed 2’ on center.

Ordering Roof Panels and Screws

Care should be taken to order panels of the correct length (We will cut to the inch) to minimize cutting after purchase. You should add 2” to the roof plane length to allow for the hem over the extended eave trim. When a roof transition is involved, panels of the upper portion should be ordered short to allow proper placement of the transition flashing. The end user is responsible to verify all measurements in the field and provide a detailed cut list when placing the order. Improper measurements or relying only on a blueprint for ordering will result in errors for which the customer is fully responsible even if we did the take-off. Our take-offs are for estimating purposes only not for ordering. Order about 70 screws per 100 square feet of roof or 2 screws per clip. Please confirm all estimates with your Marco Metals dealer when you place your order.

Ordering and Applying Trim

The most common flashing for metal roofing is the ridge cap, which is used at the peak of a roof. Extended eave is used at the eave and is often applied above the fascia. When roof pitch exceeds 5/12 the slope of the roof should be mentioned when ordering ridge cap, endwall, and extended eave. At the gable edge, the use of rake withz-rake cleat, or extended rake trim adds to the appearance of the structure and protects the fly-rafter. Sidewall flashing is used where the side of the panel butts up against an adjacent wall. Endwall flashing is used where the top of a roof slope meets a vertical wall. Transition trim is used where two different roof pitches meet along the length of the roof. Both slopes should be mentioned when ordering transition or gambrel flashing, upper pitch first (ie. lower roof at 4/12 and upper at 10/12 would be ordered "10/12 to 4/12 transition"). Valley Flashing is used at the intersection of two perpendicular roof planes. Z-bar is used with ridge and hip caps, endwall, and sidewall flashing. Offset cleats are used with valleys and transition trims. Order two z-bar for each piece of ridge (or hip) and one piece of z-bar for each piece of sidewall, endwall, or transition. Order two offset cleats per valley and one per transition. 1" wide butyl tape must be used to seal between offset cleat or z-bar and the roof panel.

Trim Installation Diagrams

Z-Bar with Ridge Cap

Caulk end of z-bar. Use perforated z-bar if venting is desired. Carefully measure from the peak and snap a chalk mark on panel ribs before placing z-bar so that the ridge cap will hook over the z-bar. Place so that slight pressure can expand the ridge up to spread over and snap to the z-bar.


Used at pitch changes. The more flat the transition, the more desirable to support the back of the transition.


Use perforated z-bar where venting is desired. Z-bar must be cut to fit between the ribs. A bead of tube sealant is advisable at each end.

Z-Rake Cleat

Panel edge is located 1.25" from edge of roof. If panel does not end at a rib it must be cut 1" long and the edge turned up 1" to fit under the cleat.


Offset Cleat

Used where a roofing panel needs to be terminated in a located other than the eave, such as at a valley or transition.


Used with offset cleats. Valley should be hemmed over the eave trim just like a panel. The end of the center V should be filled with tube sealant with flaps folded over and riveted.

Extended Eave

Roof panel should be hemmed up and hooked over the extended eave to form the drip edge.

Extended Rake

To use this trim the outside rib of the edge panel must be cut off and the edges hemmed 1" and hooked over the edge. This detail is difficult to do well without proper tools, but it makes a clean, simple rake.

Peak Cap