A metal roof is a roofing system made from metal pieces or tiles. They are components of the building envelope.
Enough corrugated zinc/aluminium sheeting to cover an average-sized house, transported by motorcycle, Cambodia, 2006
Design freedom with metal roofing, house in Darwin, Australia
Fixing corrugated metal sheeting over reflective foil sarking in Darwin, Australia
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Advantages of a Metal Roof
- Light weight
- One of the major advantages of metal roof sheeting is that, in most of its forms, it is lightweight, and therefore portable.
- Metal roof sheeting in the form of corrugated galvanized iron was a great aid to opening up countries like Australia and South Africa in their early days. This is still happening today in parts of the developing world.
- Metal roofs are used almost universally to cover large buildings because of their high strength-to-weight ratio. The roof of the new Wembley Stadium is an example. It consists of approximately 40,000m2 or 11 acres of aluminium standing seam sheets, 4 acres of which are movable. Zinc/aluminium-coated steel is the most commonly used roof sheeting material in Australia's cyclonic building codes.
- Durability
- Sheet materials like stainless steel, copper, zinc, aluminium, and lead are inherently durable; the oxidization of the base material forms a protective patina.
- Modern steel roof sheeting is coated with an alloy of zinc and aluminium to give it some of the durability of each of those materials at a lower cost and higher strength than either.
- The coatings and fixings on steel roof sheeting can be and are designed for different environments, including the harshest of industrial or marine locations.
- Design flexibility
- Large sprung curves.
- Rolled bullnose shapes.
- Copper cupolas.
- Energy efficiency—Coatings with high reflective values to steel sheeting increase the thermal efficiency of buildings in high-temperature areas.
- Fire and spark resistance
Disadvantages
- Care must be taken on large roofs to provide for thermal movement.
- Movement caused by differences in temperature may cause objectionable noises in some roofs, for example curved roof surfaces.
- Care must be taken with all metal roof products to avoid incompatible materials. Dissimilar metals can cause unexpected and rapid corrosion.
- Metal extraction, refining, and production and transport of metal roof components are energy-intensive and are almost always nonlocal.
Types of Metal Roof
- Corrugated galvanized iron. The original product, wrought iron plate coated with zinc and then roll-formed into corrugated sheets. Now rare and no longer manufactured.
- Galvanized steel. Still manufactured but rarely produced as mainstream roof profiles, except for heritage products.
- Zinc 55% / aluminum 43% / silicon 1.6% coated steel. Sold under various trade names, i.e., "Zincalume." Often left in the zinc finish, but more widely with factory coated colors, i.e., "Colorbond." AKA "Cool Metal Roofing."
- NOTE! Galvanized steel and Zinc/aluminum coated steel are NOT the same product. They are NOT compatible. Flashings, gutters, and sealants for one should not be used with the other!
- Metal Tile Sheets. For many decades, architects, contractors, and building professionals everywhere have recognized metal roofing for its low maintenance, superior weather resistance, and long life. Metal tile panels are the latest generation of metal roofing; they are functional, durable, and ideally suited to residential use. The tile sheets are manufactured by a leading European company and distributed in Australia by Coroofs.The tile sheets are appropriate for all kinds of roofs with inclination from 6 deg . Their appearance is vital for aesthetic impression of the whole building; therefore, they are also used in sophisticated detached-house designs.
- Zinc. Standing seam wall and roof sheeting.
- Stainless steel. Available for harsh conditions, roll-formed and fixed similar to corrugated steel profiles.
- Aluminum. One of the longest-lasting metals, but somewhat expensive. Aluminum roofs are lightweight, corrosion resistant, and high in reflectivity, which may help increase a building's energy efficiency.
- Copper. Usually used for flashing or very small sections like covered entryways. Expensive. At the Lyle Center for Regenerative Studies copper is used for regenerative principles of sustainable design: If the building were ever to be dismantled the copper would be reused because of its high value and variety of possible uses.
- Stone-coated steel. Stone-coated steel shingle panels are made from pressure-formed, zinc/aluminum-alloy-coated steel with an acrylic, bonded, stone chip finish, which resists fading and UV penetration. The panels are lightweight (1.5 pounds per square foot) and come in a variety of earth-toned colors. They are fireproof and come with a 120 mph (190 km/h) wind rating and have a 50 year to lifetime warranty against fading, cracking, rusting, curling, and de-granulation. Stone-coated steel panels come in a wide range of solid and Mediterranean blends and are available in tile, shake, slate, and shingle styles. They withstand all extreme environmental elements including hail, fire and wind. Stone-coated steel is ideal for converting flat roofs to pitch roofs, and it can be installed over existing roofs without the need for tear-off. Structural support is generally not required, The material can be walked on after installation. Nails are installed horizontally to provide greater resistance against vertical pullout due to high wind conditions.
- IBR (inverted box rib). A low-cost corrugated square-fluted iron roofing used mainly in the South African market. It can be commonly seen all the way from industrial sites to low-income shacks.
Maintenance
Metal roofs will need recoating once the factory finish wears off. Roof coatings are the preferred material since they are able to stay elastic and withstand the thermal cycling that occurs in metal roofs.
Metal Roof Coatings
Many different types of coatings are used to coat metal panels. These include asphalt or polymeric (elastomeric) coatings. Each coating has its advantages and disadvantages.