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Residential Metal Roofing Trim Installation

This finishing touch ties all roofing components together

Mbci  Feb19 1
(Photo courtesy of MBCI)

Metal roofing trim can give homes a finished, polished appearance with contrasting colors and interesting shapes. More importantly, this integral roof accessory provides critical protection in conjunction with metal roofing panels to strengthen and seal the entire roof. Eliminating moisture intrusion and diverting water away from a building, trim creates smooth and watertight transitions between different sections of the roof, which is critical in locations where the roof’s slope or direction changes. All of this moisture reduction reduces mold growth and decreases the risk of ceiling leaks.

So, what’s different about trim components installed on residential metal roofs versus trim components installed on nonresidential metal roofs? Ashley Harper, marketing analyst for MBCI, Houston, says trim on commercial roofs tends to be larger and more aesthetically pleasing than residential roofs. Ray Smith, managing director and owner of Jupiter, Fla.-based AppliCad USA Inc., says the style of trim used is determined by the edge being finished and the roofing material being used. “Architectural styles also dictate what sort of trim is required,” he adds.

The following instructions are general, non-comprehensive guidelines and recommendations regarding installation procedures for three common residential metal roofing trim components: ridge caps, eave trim and rake trim.

Ridge Caps

Ridge caps seal the very top of rooflines where two roof caps meet. “Often, they serve to vent the attic space also known as a vented ridge,” Harper says. “Outside closures are typically installed first to seal off the space between the panel ribs.” Incorrect ridge cap fitting and installation can lead to gaps that can allow birds to nest, pests to enter and can also lead to leaks and corrosion in building panels. Here are some overall installation steps using fasteners:

• Ridge caps should be installed so that all end laps are away from the prevailing wind.

• Align the center bend of the ridge cap directly over the center line of the roof ridge.

• Insert a magnetic 1/4-inch driver bit into a power drill. Drive one 2-inch, self-tapping metal roofing screw through both sides of the metal ridge cap into the roofing material. Each screw should be positioned 1/2 inch above the edge of the ridge cap and should be driven until the neoprene gasket on the screw begins to spread out from beneath the metal washer.

• Ridge caps should be end lapped a minimum of 4 to 6 inches.

Check to ensure all end dams and closures are correctly assembled. To prevent leakage at the ridge that could drip or run under the installed roof system or into portions of the structure, confirm the sealant is in the correct location. It should be in complete contact with the end dam, closures and the roof panel; without any voids or gaps.

(Photos courtesy of McElroy Metal)

Eave Trim

Metal eave trim (sometimes called eave drip) pieces redirect rain runoff away from the perimeter of the roof fascia. Interfacing with the gutter or drainage system, it is installed on the lowest point on the roof and must handle any runoff from the roof’s upslope portions. As a rule of thumb, eave trim should be installed prior to installing the roofing panels when possible. It can be installed both over and under the underlayment.

“The eave trim terminates the roof panel at the eave end of the panel to the wall panel,” says Ken Gieseke, vice president of sales and marketing at McElroy Metal, Bossier City, La. “It is installed onto the roof, then the inside closure is installed on top the eave trim, which when the panel is installed, will close of the open voids left by the profile of the roof panel.” While eave trim must be cut and folded to fit the fascia and gable, it requires minimal angling to make a proper fit.

Specific fasteners positioned between 12 and 24 inches apart secure the eave trim in place. Other applications can use 1 1/4-inch galvanized roofing nails to fasten the eave trims to the lowest roof purlins. Confirm the eave sealant is in the correct position on top of the eave trim, and that eave fasteners penetrate the center of the eave sealant into the eave plate.

Rake Trim

Rake trim (also known as gable trim) is a metal flashing finishing piece placed along the roofline at the sloped sides at the end of a residence’s dormer or gable. Rake trim can be flat with no overhang, or it can overhang the gable end like an eave. It is cut, angled and folded onto the roof line, and fasteners (usually evenly spaced between 12 and 24 inches apart) set it in place. Resulting in a uniform edge, “Rake trim terminates the roof panel at the end of the roof to the gable end wall panel,” Gieseke says. “The rake trim is installed over the roof panel and over the wall panel using self-drilling screws and sealant tape.” Tape applied on the underside of the nailing flange can provide a seal against moisture intrusion between the end panel and trim.

Installation Advice

Butyl sealant is a critical component of a weathertight roof, utilized anytime there is a metal-to-metal connection such as panel to trim and trim to trim. “Without the sealant, capillary action can occur resulting in moisture infiltration and leaks,” says Gieseke. “Butyl sealants are available in both tape and tube formats. Trim laps should be carefully sealed to ensure that water infiltration does not occur at lap. It may be necessary to marry the trim lap sealant into another sealant such as

marrying the trim lap sealant with the eave sealant. This process just makes sure there is not a way for water to get past a joint seal by using the inside of a trim lap.” Many homeowners worry and complain about their metal trim not matching the rest of their house. Avoid this issue by ensuring the panels and trim come from the same source. If this is not possible, find out the materials and gauges of the existing metal to help confirm.

Another residential metal trim installation concern is the field modifying of generic trim pieces to fit to a particular house. Gieseke stresses that true craftsmen can modify trim that performs as desired from a technical side and still maintain its aesthetic appeal. However, “On a residential homes that feature lower eave heights and owners that care about curb appeal, it would be the best practice to install trim designed for residential applications.” After metal trim installation, review the quality of work from the ground. It’s from this vantage point where the residence will be viewed, and mistakes can be seen.

More detailed installation instructions than what is presented here are available. Follow them; correct metal trim installation cannot be overemphasized. Read all manufacturers’ instructions thoroughly before beginning any installation. Harper stresses, “[The manufacturer’s instructions] will be the best to follow as most manufacturers have many years of experience and know what does and doesn’t work.”

(Photo courtesy of MBCI)