Metal roof
A metal roof is a roofing system featuring metal pieces or tiles exhibiting corrosion resistance, impermeability to water, and long life. It is a component of the building envelope. The metal pieces may be a covering on a structural, non-waterproof roof, or they could be self-supporting sheets.
History
Lead and Copper have played a significant role in architecture for thousands of years (see: copper in architecture). Lead was one of the first and easiest metals to smelt and with a low melting point, it could be easily formed to be watertight. As a by-product of silver smelting, in Roman times it was readily available and relatively cheap.[1]
In the 3rd century BCE, copper roof shingles were installed atop the
When iron smelting became widespread in the early 19th century, although the smelting process was complicated, ore was so plentiful that iron became cheaper than lead, and much cheaper than copper. It was later determined that iron corrosion (rust) could be stopped or at least slowed by dipping the hot iron sheets into molten tin or zinc, forming a metallurgically-bonded coating which protected it. Terne, an iron plate dipped into a solder of 80–90% lead with only the remainder tin, was cheaper than tinplate made in the same way, and the lead was more resistant in long-term outside use than tin or zinc alone. Terne became popular for roofs and weather-resistant farm items.[citation needed]
In 1829, Henry Palmer, engineer of the London Dock Company, patented "indented or corrugated metallic sheets" which added additional stiffness to bending in one direction in the manner of a beam. This allowed the sheet iron to be self-supporting when used as a roof; a contemporary account praised the material as "the lightest and strongest roof (for its weight) since the days of Adam".[7]
After Palmer's patent expired in 1843, "
Environmentally friendly
Metal roofs are 100%
Advantages
Metal roofs can last up to 100 years, with installers providing 50-year warranties.[citation needed] Because of their longevity, most metal roofs are less expensive than asphalt shingles in the long term.[10]
Metal roofing can consist of a high percentage of recycled material and is 100% recyclable.[11] It does not get as hot as asphalt, a common roofing material, and it reflects heat away from the building underneath in summertime. On a larger scale, its use reduces the heat island effect of cities when compared to asphalt. Coupled with its better insulating abilities, metal roofs can offer not only a 40% reduction in energy costs in the summer, but also up to a 15% reduction in the energy costs in the winter according to a 2008 Study by Oak Ridge National Laboratory. This finding is based on the use of a strapping system of four inches between the plywood and "cool-color" metal on top,[12] which provides an air gap between the plywood roof sheathing and the metal. Cool-color metals are light, reflective colors, like white. The study went on to say that re-sealing and insulating air ducts in the attic will save even more money.[13]
Metal roofing is also lightweight, creates little stress on the load bearing roof support structures and can be installed on top of an existing roof. A lightweight roof is very useful for large and or old structures, as it helps to maintain the overall structural integrity of the building.[14] Despite its light weight, metal roofing provides increased wind resistance when compared to other roofing materials. This is because metal roofing systems use interlocking panels. Metal Roofing Sheets are also resistant to any kind of attack by pests and insects.[15]
Material types
Metal roofs are sometimes made of corrugated galvanized steel: a wrought iron–steel sheet was coated with zinc and then roll-formed into corrugated sheets. Another approach is to blend zinc, aluminum, and silicon-coated steel. These products are sold under various trade names like "Zincalume" or "Galvalume". The surface may display the raw zinc finish, or it may be used as a base metal under factory-coated colors.
Standing seam metal roof
Standing seam metal roofs come in sheets up to or sometimes more than 30 feet (9.1 m) long and widths of 12, 14, 16 or 18 inches (300, 360, 410 or 460 mm). The standing seam is typically 1+1⁄2 or 1+3⁄4 inches (38 or 44 mm). They are more expensive upfront for installation and material costs but last longer than Asphalt shingles, over the 50+[clarification needed] year lifespan they are less expensive than asphalt shingle roofs. They require less maintenance than corrugated metal roofs because of the exposed fasteners on that roof.
Mechanically seamed
Mechanically seamed roofs are seamed together using a roof seamer and can be either single lock or double lock seamed, meaning they can be folded under once to be seamed together or folded under twice for extra weather protection. This is the most expensive of the three types but is the most weather resistant.[citation needed]
Snap locked with fastener strip
One side of the standing seam sheet is snap locked into the other standing seam sheet that is fastened to the roof, concealing those fasteners, and the other side of the sheet is fastened to the roof with screws, and the next sheet will cover those screws as well. The fastener screws shouldn't be screwed in too tightly to allow the sheet to expand and contract with the changing temperatures, each fastener slot has some room to move past the screw to adjust for thermal expansion. The fastener heads breaking off potentially is the down side to this method if installed improperly or from wear and tear from the fluctuating climate.[citation needed]
Snap locked with clips
Snap locked with metal clips fastened to the roof allows for more thermal expansion than fastener strip standing seam metal roofs. The fasteners and clips are both hidden under the metal roof sheets, and this option is marginally more expensive than the fastener strip snap locked standing seam roof.[citation needed]
Thin-film solar on metal roofs
With the increasing efficiencies of
Type[18] | Cost per watt |
Efficiency | Average 6 kW system cost |
---|---|---|---|
Polycrystalline | $2.80–$3.00 | 13–17% | $17,400 |
Monocrystalline | $3.00–$3.50 | 17–22% | $19,000 |
Thin-film panels | $2.00–$3.00 | 10–18% | $17,000 |
Corrugated metal roof
Corrugated metal roofs are similar in price to asphalt shingle roof installation. The fasteners are screwed through the metal into the roof requiring more maintenance to make sure the screws stay secured. Corrugated metal roofs can last 30–45 years with proper maintenance.[citation needed]
Stone-coated metal roofing
Metal tile sheets can also be employed. These are usually painted or stone-coated steel. Stone coated steel roofing panels are made from zinc/aluminium-coated steel with an acrylic gel coating. The stones are usually a natural product with a colored ceramic coating. Stainless steel is another option. It is usually roll-formed into standing seam profiles for roofing; however, individual shingles are also available. Other metals used for roofing are lead, tin and aluminium and copper.
Copper roofs
Copper is used for roofing because it offers corrosion resistance, durability, long life, low maintenance, radio frequency shielding, lightning protection, and sustainability benefits. Copper roofs are often one of the most architecturally distinguishable features of prominent buildings, including churches, government buildings, and universities.
Coating
Several types of coatings are used on metal panels to prevent rust, provide waterproofing, or reflect heat. They are made of various materials such as epoxy and ceramic.
Ceramic coatings can be applied on metal roof materials to add heat-reflective properties. Most ceramic coatings are made from regular paint with ceramic beads mixed in as an additive.
Coatings are sometimes applied to copper.[21][22] Clear coatings preserve the natural color, warmth, and metallic tone of copper alloys. Oils exclude moisture from copper roofs and flashings and simultaneously enhance their appearance by bringing out a rich luster and depth of color. The most popular oils are lemon oil (like USP), lemongrass oil (such as East Indian), paraffin oils, linseed oil, and castor oil. On copper roofing or flashing, reapplication once every three years can effectively retard patina formation. In arid climates, the maximum span between oilings may be extended up to five years. Opaque paint coatings are primarily applied over copper when substrate integrity and longevity are desired but a specific color other than the naturally occurring copper hues is required.[23] Lead-sheet covered roofs are not considered metal roofs today, but since lead bonds metallurgically (see solder) thin lead coatings on copper are very long-lasting. Lead-coated copper can be used when the appearance of exposed lead is desired or where copper-contaminated water runoff from bare copper alloys would ordinarily stain lighter-colored building materials, such as marble, limestone, stucco, mortar, or concrete.[24] Zinc-tin coatings are an alternative to lead coatings since they have approximately the same appearance and workability.[25][26]
See also
- Corrugated galvanised iron
- Green building
- Metal Building Manufacturers Association
- Metal Construction Association
- Metal Roofing Alliance
- Reflective surfaces (geoengineering)
- Roof seamer
- Rubber shingle roof
References
- ^ "Lead:The Facts" (PDF). International Lead Association. Archived from the original (PDF) on 2017-02-20.
- ^ Seale, Wayne (2007). The role of copper, brass, and bronze in architecture and design; Metal Architecture, May 2007
- ^ Copper roofing in detail; Copper in Architecture; Copper Development Association, U.K., www.cda.org.uk/arch
- ^ Copper Roofing in Detail; Copper in Architecture; Copper Development Association, U.K., www.cda.org.uk/arch
- ^ Kronborg completed; Agency for Palaces and Cultural Properties, København, "Kronborg completed – Agency for Palaces and Cultural Properties". Archived from the original on 2012-10-24. Retrieved 2012-09-12.
- ^ Agency for Palaces and Cultural Properties, Renovation of the Tower of Christianborg Palace., "Renovation of the Tower of Christiansborg Palace – Agency for Palaces and Cultural Properties". Archived from the original on 2013-01-06. Retrieved 2012-09-10.
- ^ a b c d David Miles (March 7, 2008). "History of Corrugated Iron". World Archaeology (28).
- ^ Colin Flavin (2017-04-02). "Diamond in the Rough: Albert Frey's Desert Masterpiece".
- ^ "Top Environmental Benefits of Metal Roofing".
- ^ "Metal Roofs – Bob Vila". 9 July 2013.
- ^ CNBC.com, Eilene Zimmerman, Special to (11 July 2013). "Coal, Cow Barns, Fishing Nets: Latest Home Design". CNBC.
{{cite web}}
: CS1 maint: multiple names: authors list (link) - ^ "Metal Roofing Pros & Cons: Facts, Myths – Metal Roofing Buying Guide". 3 January 2017.
- ISBN 978-0-918249-58-6. Archived from the originalon 2016-05-05.
- ^ Miller, Todd (22 February 2017). "Low Weight Metal Roofing – Arthur Thomson". Todd Miller.
- ^ "Roofing Sheets: Their types, applications and costs in India". Economic Times India.
- ^ "Thin-Film Solar Panels | American Solar Energy Society".
- ^ "Pros and Cons of Metal Roofs for Your Home".
- ^ "Solar Panels vs. Thin-Film Laminates: Costs, Pros & Cons, Top Brands". 19 January 2022.
- ^ Austin, Jim (2006). Copper: The peacock of metals, Metal Roofing, April–May 2006; www.metalroofingmag.com
- ^ Copper roofs are cool, Architecture: Working with Copper, Copper Development Association, 2009; http://www.copper.org/publications/pub_list/pdf/a4094.pdf
- ^ Clear coatings on copper alloys – Technical Report; Copper Application Data, A4027; Copper Development Association
- ^ Clear organic finishes for copper and copper alloys; Application Data Sheet 161/0; Copper Development Association Inc.
- ^ Finishes – Coatings, Copper in Architecture Design Handbook, Copper Development Association Inc., http://www.copper.org/applications/architecture/arch_dhb/finishes/finishes.html#ctngs Archived 2012-10-16 at the Wayback Machine
- ^ Sternthal, Daniel (2000). Copper flashings in contemporary construction, The Construction Specifier, Magazine of the Construction Specifications Institute, October 2000
- ^ The glory of copper; Metal Roofing Magazine, December 2002/January 2003
- ^ Sternthal, Daniel 2000. Copper flashings in contemporary construction, The Construction Specifier, Magazine of the Construction Specifications Institute, October 2000