One of the biggest reasons metal roofing is commonly chosen in commercial applications is due to its superior weather resistance to wind and water, especially in areas where hurricanes or other tropical weather is a concern. Even when the structure isn’t in a tropical location, metal roofing gives business and building owners the peace of mind that their roof is destined to last and not need constant upkeep. Common uses:
- Schools and universities
- Government buildings
- Military structures
- Transportation buildings
Metal roofing begins as a metal coil or sheet, it has the ability to be formed and cut into many different shapes, sizes, and lengths. Also, variety, along with the durability, variety of colors, and eco-friendly qualities.
Like structural applications, barns and other agricultural buildings are common uses for metal roofing (especially lap seam or exposed fastener panels).
Structural metal roofing, is when metal panels are installed over open framing or on structures that span long lengths and are attached directly to the frame or purlins (additional support beams added to the roof frame).
Metal Panel Seam Types
A seam on a metal roof is the side rib at which two metal panels come together and are connected. Seams are formed using a roll former and are then snapped together or mechanically seamed together.
Snap-lock – Metal roofing panels that have been carefully roll formed with specific panel profile edges that snap together and require no hand or mechanical seaming during installation.
Mechanical Seam – Mechanically seamed panels are also roll formed with specific edges that line up with each other on the roof. Once the two edges are put together, a hand or mechanical seamer is used to bend the edges and lock the panels together.
There are two kinds of mechanical seaming:
- Single Lock / 90-degree seam – One folds of the seam
- Double Lock / 180-degree seam– Two folds of the seam
Tee Panel – A type of standing seam where two panel edges come together and are connected at the top by a cap, mechanically seamed in place to lock the panels together.
Exposed Fastener Lap Seam – Exposed fastener lap seams are when the overlapping ends of the lap panels are fastened down to the deck from the top of the panel.
Metal Roofing Panel Rib Rollers
Rib rollers are the “patterns” or striations roll formed into a metal roofing panel between the seams. These can be used to assist with the installation of a metal roof.
Common rib rollers include:
Flat – No indents between the seams
Ribbed – Some shape or indentation between the seams
- V-Ribs – “V” shaped panel indents
- Bead – Longer, rectangular panel indents
- Pencil – Circular panel indents
Striated – Small consistent indentation lines in the panel (can help reduce oil canning)
Corrugated – Larger, constant waving of the metal panel
Clip relief – A stiffening rib adjacent to the seam that allows the space for a clip
UNDERLAYMENT – Underlayment is the layer of material that goes underneath the metal panels and provides protection from water and moisture, ice, high temperature, and vapors. Underlayment is generally installed mechanically or self-adhered with a glue backing on the roof deck. Common materials are felt, synthetic (polypropylene or polyethylene), and fully-adhered peel and stick.
CLIPS – Clips are used to attach the metal roof panels to the roof deck. Clips are put on the standing seam portion of the bottom panel, which is then attached to the roof deck by fasteners. After the clip is put on the bottom panel, the top panel is placed over the clip and the two panels are snapped together or mechanically seamed into place, which securely attaches it to the structure.
FASTENERS – Fasteners are the screws used to attach the metal roof to the roof deck during installation.
RIVETS – Rivets are similar to fasteners, but require a special rivet gun to install.
SEALANT – Sealants are used during installation to seal out water, dirt, wind, and other substances that can get into small spaces, making the roof as weather-tight as possible. Sealants, which are typically made up of silicone or polyurethane, come out of the tube as a flexible sealing compound that will cure after application. Most sealants are available in colors matching the roof panels.
BUTYL TAPE – Butyl tape is used in a similar fashion as sealant by sealing cracks and seams on metal roofing. It’s also commonly used for trimming purposes. It differs from sealants because it’s in the form of one or two-sided tape and seals by compression.
CLAMPS – Clamps are small metal parts that are tightened and attached to the top of the metal roof at its standing seam. These clamps have screws at the top used to attach extra roofing items such as a snow retention system, solar panels, satellite dishes, signs, AC units, etc.
PIPE BOOT – A pipe boot is the cone-like fitting that is installed around an exhaust pipe that exits through the roof. These products are typically made up of EPDM rubber (silicone is also available for high-temperature applications). The pipe boot, which can be purchased in a color matching the roof, is cut to fit the diameter of the exhaust pipe and is then sealed to the pipe and the metal surface.
Common Roofing Parts and Terms
This illustration highlights the important parts and components of a roofing structure.
FASCIA – The trim right below the roof that runs the perimeter of a structure to help keep water from running into the structure.
DRIP EDGE – A long piece of metal that is installed so water runs into the gutter and away from the fascia.
EAVE – A portion of the roof that extends past the supporting wall.
VALLEY – The internal angle at which two sloping roof planes meet.
HIP – The external or jutting angle at which two sloping roof panels meet.
RIDGE – The highest portion of a roof where at least two roof panels come to a point (commonly a horizontal line).
GABLE – The triangular section of a wall between the edges of a sloping roof. The trim occupying this article is typically called “gable or rake trim”.
CRICKET – A peaked saddle construction installed between a chimney and the roof surface to prevent against the accumulation of snow and water.
FLASHING – Sheet metal that is used to seal different portions of the roof, i.e. chimneys, valleys, etc., and provide extra weather-tightness.
CURB – An accessory used to mount additions (AC units, fans, signs) and provide a level resting structure on a sloped roof.
ROOF DECKING – The base or foundation that the underlayment and roofing material are attached to. Common roof deck materials are metal, plywood, and oriented strand board (OSB).
PITCH – The slope of a roof, which is measured using the roof’s rise divided by its run.