Installation Guide

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Tuff-Rib® Panel

Marco Metals Tuff-rib® panels are a strong, durable, economical, and attractive answer to the growing demand for metal roofing needs in the Eastern United States. Extremely versatile, they are suitable for homes and businesses as well as agricultural and utility buildings. Tuff-rib® panels give 36-inch coverage with ¾ inch ribs on 9 inch centers. An anti-siphoning channel provides protection from severe weather conditions. Both panels and trim are fabricated using state-of-the-art computerized equipment at our facility in Harrisonburg, Virginia to assure uniformity and consistency. Panels are roll-formed to the lengths specified by customers in either Acrylic-coated Galvalume® or any of our twenty one colors of painted Galvalume® in 29-gauge and 26-gauge high-tensile metal. We also offer Kynar® painted 26 gauge Tuff-rib panels in several colors. Your Marco Metals dealer will be happy to assist you in making the best choice for your particular roofing needs. Marco Metals Tuff-rib® 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 most painted metal carries a 40-year warranty. Marco Metals stocks a complete line of fasteners, sealants, sliding door parts, 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.

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. Stitch screws and butyl tape are optional for side laps when the pitch is 4/12 or greater. Stitch screws and butyl tape are recommended on side laps when the pitch is less than 4/12. As a general principle, the lower the pitch the more necessary that screws and tape be used on the side-laps. Consult your dealer for recommendations for your particular roof. Tuff-rib panels come equipped with an anti-siphon groove that must be kept free of caulk, tape and other debris for it to function properly.

Roof Preparation

Oil-canning is a wave-like, rippled appearance extending up the length of the 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 felt paper, etc., can promote oil-canning or dimpling. Careless storage and handling can also contribute to oilcanning. Care should be taken to provide a flat, uniform surface on which to attach the panels. 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. Tuff-rib panels may be installed directly over shingles if a synthetic underlayment is placed between the metal and the shingles or Steel- Shield® is applied to the back of the metal. Screws must be long enough to penetrate completely through the metal, shingles and the roof deck. WARNING: Installing Tuffrib directly over shingles greatly increases the chance of oil-canning and dimples in the metal. Battens may also be used for installation over shingles. 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. 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 Tuff-rib 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. In applications where end-lapping is necessary, the upper panel should lap over the lower panel by a minimum of 6 inches. Lower pitches require a greater amount of panel overlap. All end-lap applications should use two horizontal rows of butyl tape across the panel and proper fastening to provide a maximum water seal. An overhang of 1.5 inches on the eave is recommended to provide a drip edge. The open panel ribs at the eave can be sealed with inside closures.


Metal panels exposed to air will experience condensation of moisture under certain conditions. To avoid this, installation of plastic coated insulation or some other product to keep moist air from contacting the panel is helpful. Drip Stop® works well to absorb condensation and prevent dripping. As with any other type of roof, adequate ventilation through the attic cavity below is essential for proper function and long service life.


Specially-washered 1 ½” screws applied through the flat of the Tuff-rib panel are the recommended method for attaching roofing panels. Marco Metals carries wood screws in 5 different lengths: 1”, 1 ½”, 2”, 2 ½”, and 3”(3” is a special order). Self-tapping screws are available for fastening to steel substrates. 1 ½” screws are the best all-purpose size but make sure that the screw shank will penetrate at least 1” into the substrate. 2 ½” screws are necessary for attaching ridge caps and endwall/transition flashing. Screws can be placed on the overlap side of each rib for the interior rows. See Figure 1a. Screws should be placed on both sides of each rib at eave and endlaps. See Figure 1b. Butyl tape with stitch screws can be used to fasten side laps on pitches below 3/12 if care is taken that butyl tape does not block the anti-siphon groove of Tuff-rib panels. Butyl tape with stitch screws are recommended for all R-panel side laps. DO NOT OVERDRIVE SCREWS. See Figure below for proper screw installation.
Fastening of polycarbonate skylight panels is a bit different. Temperature change causes significant expansion and contraction, therefore allowance must be made for thermal movement. Pre-drill holes to allow for expansion and contraction by making them at least 5/64” larger than screw. Special screws with larger washers are available for this application. Drill holes through the top of the rib for roofing and through the flat for walls. Be careful NOT to stress the panel by tightening screws too tight. Do not use any caulk with acetone or diethyl ether as a curing agent because this will cause the panel to harden and crack very quickly. We stock caulk compatible with polycarbonate skylight panels. Butyl tape is a good choice at end laps provided the tape is not exposed to sunlight. Do not screw metal and polycarbonate panels together. Screws must be placed above and below, or beside overlaps because the metal and plastic do not expand and contract at the same rate and need opportunity to move past each other.

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. Panel lengths should fall 1-2 inches past the eave to allow a sufficient drip edge. When a roof transition is involved, panels of the upper portion should be ordered short to allow proper placement of the transition flashing. Two ways to figure the amount of screws needed for 2’ oncenter spacing is to multiply the total linear feet of panel by 2.4 or the figure 70 screws per 100 square feet of roof covered.
Example: your order is 1250’ of Tuff-rib roofing to be installed on purlins placed 2’ on-center.
1250 x 2.4 = 3000 screws 3000 ÷ 250 = 12 bags
Example: Your order is for a roof of 4162 square feet with rows of screws spaced 2’ on center.
4162 ÷ 100 = 41.62 square. 41.62 x 70 = 2913 screws
2913 ÷ 250 = 11.66 or 12 bags
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. Drip edge is used at the eave and is often applied above fascia trim. When roof pitch exceeds 5/12 the slope of the roof should be mentioned when ordering ridge cap, endwall, and drip edge. At the gable edge, the use of rake & gable or narrow outside corner 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. For both gable and sidewall trim the installer should be careful to seal between the flashing and the roof panel with butyl tape before fastening. Endwall flashing is used where the top of a roof slope meets a vertical wall. Transition flashing is used where two different roof pitches meet along the length of the roof. Both slopes should be mentioned when ordering transition 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 and should be sealed between the flashing and the roof panel with a row of butyl tape and expanding foam closure. To prevent penetration of water, insects, and debris, outside closures should be inserted between the ridge cap or endwall/transition and the top end of the panel. Inside closures are used for the same reason over drip edge or the top of transition flashing. For endwall, transition and ridge, screws are applied through the trim, closure, and rib in at least every other rib of the panels. 2 ½ inch screws should be used for attaching ridge caps. Various types of vented ridge closures are available if needed.

Trim Installation Diagrams

Ridge Cap

Drip Edge

Rake and Gable


Angle (Fascia)

Double Angle (Wainscoat)

Carolina Snow Guard


Rat Guard

Drip Flashing

Round Door Track Cover

J Channel

Soffit Trim

F-J Trim