CANADIAN SHEET STEEL BUILDING INSTITUTE'S BLOG - New articles are now posted on the CSSBI website at www.cssbi.ca/blog
Tuesday, 23 December 2014
Thursday, 18 December 2014
Toiture en acier - plusieurs styles
Une tôle d’acier profilée est fixée à la structure portante à l’aide de vis à travers les nervures de la tôle. Les têtes de vis peuvent être peintes de la même couleur que la tôle. Les panneaux sont habituellement d’une largeur de 30 pouces ou plus et leur longueur peut être spécifiée selon l’application. Ce type de système de toiture en acier est très populaire pour de nombreuses applications au Canada.
Profilés à motif en tuiles
Panneaux d’acier prépeints profilés pour ressembler aux tuiles d’argile ou de béton souvent utilisées dans les constructions résidentielles. Le grand choix de largeurs et de longueurs élimine les nombreux joints que requièrent les toitures en tuiles d’argile ou de béton. De plus, leur poids plus léger permet de préserver la structure du toit. De nombreuses textures et couleurs sont offertes.
Ce type de toiture se caractérise par son motif d’ombres linéaires. Une grande variété d’espacements et de modèles de nervures et de joints scellés est offerte. Ces joints peuvent être plats ou cachés, ou en lattis larges. Les design et les systèmes d’ancrage varient d’un fabricant à l’autre. La hauteur et la largeur des joints scellés, de même que leurs couleurs sont très variées, permettant ainsi de satisfaire tous les goûts.
Les bardeaux d’acier ont été conçus comme alternative aux bardeaux d’asphalte communs, mais avec la résistance et la longévité des panneaux de toiture en acier. Les bardeaux d’acier sont plus légers que les bardeaux de toiture en asphalte, en cèdre et en ardoise et que les tuiles de béton et d’argile. Ils ne pourrissent pas, ne gondolent pas, ne se fendillent pas, ne se déchirent pas, ne s’écorchent pas, ne pèlent pas et ne se perforent pas dans des conditions d’usure normales et avec un minimum d’entretien.
Wednesday, 17 December 2014
The Many Styles of Residential Steel Roofing
There are several styles and colours of vertical rib, standing seam, steel shingle and tile profile that complement any style home. The only difficulty is deciding which one is best for your home!
A profiled steel sheet is fastened to the supporting structure with screws through the ribs of the sheet. These screws can have heads painted to match the colour of the sheet to blend in. Panel widths are typically about 30 inches wide or greater and can be supplied in custom lengths to fit the application. This type of steel roofing system is very popular in many applications all across Canada.
Pre-painted steel panels formed to create the appearance of clay or concrete tiles are often used in residential construction. The wide sheet widths and long lengths eliminate the many joints found in clay and concrete tile roofs. In addition, their reduced weight spells savings in the roof structure. There is a wide variety of colours and textures available.
Standing Seam Roofing
These designs are characterized by their linear shadow patterns. They vary greatly in the spacing and the design of the ribs or standing seams. These seams vary from flat, hidden seams to wide battens. There is a variety among manufacturers as to the design and the anchoring systems. The height and width of these standing ribs, as well as their colour will express a broad spectrum of aesthetic expressions.
Steel shingles are designed as an alternative to common asphalt shingles, but with toughness and long-lasting qualities of high-strength steel roofing panels. They are lighter than asphalt shingles, concrete and clay tiles, cedar shakes and slate roofing. Steel shingles will not rot, curl, crack, break, chip, peel or perforate under normal use and minimal maintenance. There is a wide variety of colours and textures available.
If you are looking for more information about residential steel roofing, please visit our website dedicated to the topic. www.steelroofsource.com
Tuesday, 9 December 2014
Sheet Steel Gauges - What They Mean
Within the construction industry there is often confusion over gauges, gauge numbers and the related thickness. The industry has been trying to move away from gauge numbers, without complete success. The following information will show why sheet steel products should be specified to the decimal thickness.
Manufacturers’ Standard Gauge For Steel Sheets
The most common gauge system used in Canada for structural sheet steel products is the Manufacturers’ Standard Gauge (MSG). The MSG for steel sheets was developed having a DEFINITE THICKNESS equivalent for each gauge number. In the standard gauge system the density of steel is taken as 489.6 lbs/ft3, or 40.80 lbs/ft2/in. However, since sheet weights are calculated on the basis of specified width and length, with all shearing on the over side, and also since sheets are somewhat thicker at the centre than they are at the edges, a further adjustment was made to obtain a closer approximation for inter-changeability between weight and thickness. Over a long period of time this value for sheets has been found to be close to 2.5 per cent heavier than 40.80 lb/ft2/in. A figure of 41.820 lb/ft2/in is the one commonly used to express the relationship between weight and thickness for steel sheet.
The Galvanized Sheet Gauge
The Galvanized Sheet Gauge is an older system used primarily by the trades consuming non-structural galvanized steel and is a measure of the zinc coated sheet thickness. It was developed in the early days of galvanizing before sophisticated wipers were available and, consequently, zinc thicknesses were thicker than today. The GSG system was used on some of the older gauge charts published years ago that unfortunately still seem to get used even today.
Thickness Definitions
There are a number of terms used for sheet steel products that need to be explained because they will affect the thickness of product that could be delivered to the job site.
Nominal Thickness: When sheet steel is produced by the steel companies it is manufactured to a target or “nominal” thickness. As with all manufacturing processes, variations in the final thickness of the sheet are unavoidable. However, the thickness is controlled very tightly to ensure that it does not fall below the minimum thickness (as described below).
Base Steel Thickness: The thickness of the sheet steel material without any coatings.
Coated Thickness: The thickness of the steel sheet including any metallic coatings (i.e. zinc or aluminum-zinc alloy) and paint coatings.
Design Thickness: The design thickness is the thickness of the base steel only, and is used by the engineer to determine the structural properties of the cold formed product. This is the thickness that a manufacturer will list in their product catalogues and load tables.
Minimum Thickness: The minimum thickness of structural sheet steel building products delivered to the job site will be the design thickness minus the maximum allowable under-tolerance specified by the CSA-S136 Standard or the material specification, whichever is the more restrictive. The minimum thickness allowed by the CSA-S136 Standard is 95% of the design thickness.
Thursday, 20 November 2014
CSSBI Member ArcelorMittal Dofasco to supply cauldron for the 2015 Pan Am/Parapan Games
ArcelorMittal Dofasco has become a partner with and official supplier to the Games. Our company will provide the steel for the Games’ most iconic symbol, the Cauldron. In addition, a second Cauldron will be made and permanently displayed in Hamilton.
There will be up to 14 tons and 10 types of our steel in the Cauldrons, including our Galvalume®, hot roll, cold roll enameling and tubular products. The cauldrons will represent Canada and the many nations and communities coming together to transform tomorrow through sport.
Hundreds of millions of households across the Americas are expected to watch as the cauldron is lit for the first time on July 10, to officially open the Pan Am Games. It will be lit a second time on August 7 to welcome the best athletes in the region to the Parapan Am Games. The lit cauldron will also open and close daily television broadcasts.
This is a partnership with an event that embodies the strength of people, nations and human spirit. The 2015 Pan Am / Parapan Am Games are the first major international Games to be hosted in Ontario since the British Empire Games hosted in Hamilton in 1930.
Wednesday, 29 October 2014
Galvanic Compatibility of Galvanized Steel and Aluminum
Galvanic Compatibility of Galvanized Steel and Aluminum
By X.G. Zhang, Cominco Ltd.
Zinc and aluminum are galvanically compatible materials in atmospheric environments. That is, when these two metals are in direct contact there will be very little galvanic corrosion of either metal resulting from the coupling.
As shown in the Table 1 below, the amount of corrosion of both zinc and aluminum when coupled to each other is close to that of the controls, indicating that there is very little galvanic corrosion. This is in contrast to the coupling with copper for which the amounts of corrosion on both zinc and aluminum are greatly increased due to the galvanic action. The reason for the low galvanic action between zinc and aluminum is primarily due to a lower position in the electromotive force series of aluminum relative to zinc and the formation of an inert passive film on the surface of aluminum.
Table 1
Galvanic corrosion rates of zinc and aluminum tested for one year in an urban atmospheric environment, in m/y [1].
Aluminum
control 0.2
coupled to zinc 0.0
coupled to copper 5.3
Zinc
control 1.2
coupled to aluminum 1.1
coupled to copper 2.0
Test in a wire-on-bolt assembly
Because of their galvanic compatibility, zinc and aluminum can be used together in atmospheric environments without significant galvanic corrosion problems. The situation is even better when the metals are painted. Since paint is generally not conductive, it prevents the electrical and/or electrolyic contact between the two metals which is required for galvanic action. Therefore, painted aluminum and galvanized steel can be used in direct contact without causing galvanic corrosion problems as, for example, shown by the sketch above in the case of a galvanized steel fascia in contact with a painted aluminum eavestrough. Some galvanic action may occur at places where the two painted metal products are joined by metallic screw fasteners or nuts and bolts. At these places the amount of galvanic corrosion should be close to the values indicated in the table and the extent of galvanic action is limited to within a few millimetres of the contact line [2].
References:
1. V. Kucera and E. Mattsson, “Atmospheric Corrosion of Bimetallic Structures”, in Atmospheric Corrosion, W.H. Ailor (ed.), pp.561-574, John Wiley & Sons, New York, 1982.
2. X.G. Zhang, “Galvanic Protection Distance of Zinc Coated Steels Under Various Environmental
Conditions”, Corrosion’98, Paper No. 747, NACE, 1998.
Wednesday, 22 October 2014
Natural Finish Metallic Coatings – Attractive but not Architectural
Variations in Surface Appearance Caused by Viewing Angle
This blog post is to provide guidance in material selection and provide information on the Architectural Metallic Finishes that are available for highly visible steep slope roofing and cladding applications.
The recommended product for these applications is prepainted steel available in a wide variety of metallic finishes that are consistent in colour, gloss, reflectivity and overall appearance from panel to panel, regardless of the building elevation. A selection of metallic colours is shown below. It is important to note that the actual colours and finish may vary from these printed samples. If an exact colour match is required, contact a CSSBI Fabricator Member.
Prepaint Coatings
Prepaint coatings are applied to steel by a continuous coil coating process under strict quality control conditions. These Architectural (exposed quality) finishes are offered in a variety of metallic colours including, for example, Bright Silver. Depending on the end use requirements, metallic colours are available with either fluorocarbon (Kynar) or polyurethane paint systems to match silver, copper, bronze, aluminum, zinc or other metallic finishes. The prepaint systems are designed to match a colour standard and quality control measures during the paint process provide consistency across the width of the coil, along its length and from coil to coil. Each new batch of paint is also produced to the same colour standard to minimize batch to batch variation. Even with these quality control procedures in place, caution should still be exercised if more than one production order must be used for the same building. For recommendations, see Appendix A2 of CSSBI 20M-99 “Standard for Sheet Steel Cladding for Architectural, Industrial and Commercial Building Applications”.
Architectural prepaint systems also come with an exterior weathering performance specification that specifies a maximum colour change, chalking and film integrity as long as 35 years.
Architectural prepaint systems have proven and predictable weathering performance. They provide a consistent colour match to metallic finishes and should be the product of choice for applications that require uniform appearance.
Natural Hot Dip Metallic Coatings
The most common hot dip coatings used for building products like roofing and cladding are zinc and 55% aluminum-zinc alloy coatings. Both products are produced by the continuous hot dip galvanizing process. The quality control measures provide for good coating adhesion necessary for forming into profiles, and coating weight (thickness) to meet the appropriate ASTM coating designation for long service life.
Although there are manufacturing process metrics to control surface appearance, there is always normal variation in spangle size from coil to coil and within a coil. The natural metallic finish can therefore vary depending on steel substrate thickness and chemistry, pot chemistry and temperature, and other operating parameters as well as the roofing or cladding panel orientation (see image at the top). Unpainted hot dip coated steels are also passivated with a very thin inorganic or organic system to provide protection against storage stain. In spite of this, the weathered appearance of the metallic coating can become nonuniform over time and would not be consistent with an architectural finish.
In summary, unpainted natural finish hot dip metallic coatings are attractive and are used for a variety of commercial, industrial, and agricultural buildings for roofing and cladding. However, they are not considered to have an exposed architectural finish. If a uniform visual appearance is required over the long term, prepainted steel should be specified. A wide selection of prepainted steel having metallic finishes are currently available and new or unique metallic colours can be quickly developed to suit high profile projects.
Click to download Fact Sheet 24: Natural Finish Metallic Coatings – Attractive but not Architectural
Wednesday, 15 October 2014
Steel Cladding – A Farmer’s MVP (Most Valuable Product)
The Canadian Sheet Steel Building Institute commissioned a non-biased third party, Strategic
Research Associates, to examine the state of the Canadian farm. Specifically, the study examined farmers’ steel cladding purchasing habits and steel cladding usage over the past 10 years. The study queried 471 farms across Canada with 43 farms in British Columbia; 96 in Alberta; 96 in Saskatchewan/Manitoba (combined); 97 in Ontario; 96 in Quebec; and 43 in the Atlantic Provinces. The results are within ± 4.5 percentage points for complete representation of all Canadian farms and are as follows:
Since 1996, there has been a significant shift in farm type across the nation. Livestock farms have dropped by almost 20%, and the balance has shifted to a greater number of mixed crops (up to 28%) and cash crops (up to 39%) respectively. The study found that overall, there are fewer farms across Canada; however, the farms that do exist are considerably larger.
The Purchase of Steel Cladding
Strategic Research Associates note that a 10-year period is too long to adequately explain strong trends in increases of steel cladding purchases. However, the results are quite interesting as a whole as well as regionally. In 1996, only 47% of Canadian farmers said they had purchased cladding in the last 10 years. By 2006, that percentage of farmers grew to 79%.
Regionally, it was found that the nation’s three major markets are consistent with the overall average as shown in the previous graph. The study noted that significant growth occurred in the Quebec market. This is explained through the expansion of swine and dairy operations and the replacement of existing building stocks.
Steel, the Right Choice
While the study showed moderate increases in steel cladding purchases on the farm, the question remained on ‘how’ popular it was compared to other types of exterior cladding such as wood, vinyl, or aluminium. Results concluded that steel cladding is the top seller and gaining market share at the
expense of vinyl and aluminium. In 2006, 88% of Canadian farmers preferred steel cladding for their farm structures, which is up from 1996 by 9%. (See Figure 3.)
The types of farm buildings steel cladding is used for is consistent with 1996 numbers:
- 80% use it for machinery sheds
- 69% for storage buildings
- 65% for barns
- 26% for houses
- When given a choice, Canadian farmers choose Canadian steel
- 90% of Canadian farmers are either satisfied or very satisfied with their steel cladding
Wednesday, 1 October 2014
Residential Steel Roofing Installation Considerations
Underlayment is a general term used to describe a membrane installed between the steel sheets and the sheathing (plywood or OSB) or roof framing. There are a variety of materials used to manufacture underlayments with the most common being an asphalt impregnated organic fibre (roofing felts). The minimum weight of roofing felt should be equivalent to a #30 (30 pound). There are also premium synthetic products available that provide improved performance where required or desired.
The underlayment also provides a valuable second layer of protection against water getting into your home whether from wind-driven rain or from any condensation that may still occur on the back of the steel sheets. The only situation where an underlayment may not be necessary is an un-heated building (e.g. garage or storage shed) that does not contain any source of moisture (e.g. livestock or humid materials) or materials that could be damaged from possible moisture.
Wednesday, 24 September 2014
Two new Design in Cold Formed Steel Seminars Scheduled
Our sister organization, the Cold-Formed Steel Engineers Institute Canada is hosting a Design in Cold Formed Steel Seminar. Below are the details.
Design in Cold Formed Steel: Using the North American Specification for the Design of Cold-Formed Steel Structural Members CSA Standard S136-12
When & Where
Tuesday, November 25, 2014 in Fredericton, NB
Wednesday, November 26, 2014 in Halifax, NS
Registration:
CFSEI Members - $225
Non-Members - $275
Each registrant will also receive a comprehensive set of lecture notes full of explanatory material and worked examples.
Registration is limited to 50 people on a first-come first-serve basis.
About the Seminar
The primary objective of this seminar is to make the designer conversant with the latest edition of CSA Standard S136-12 (North American Specification for the Design of Cold-Formed Steel Structural Members). This is a harmonized document between Canada, the US and Mexico, and supersedes the 2007 edition (including Supplement 2010). The Specification was developed through a joint effort of the American Iron and Steel Institute’s (AISI) Committee on Specifications and the Canadian Standards Association’s S136 Technical Committee. In comparison to the 2007 edition of S136 (including Supplement 2010), a number of significant changes have been incorporated into the North American Specification, in part due to the harmonization process and in part due to latest research developments.
The intent is to bring the participant up-to-date with the current design provisions contained in the new North American Specification for the Design of Cold-Formed Steel Structural Members (S136-12), highlighting significant changes from the 2007 edition of S136. As well, numerous illustrative examples will be presented.
- Introduction
- Materials
- General Design Considerations
- Elements in Compression
- Members in Tension
- Members in Bending
- Members in Compression
- Combined Bending and Compression
- Connections
- Member Bracing
- Testing and Fatigue
- Direct Strength Method
Also, the latest Editions of the AISI North American Design Standards for Cold-Formed Steel Framing will be reviewed since these design standards are referenced by CSA S136 for use in Canada.
8:00 am Registration and coffee
8:30 am Seminar begins
10:15 am Break
12:00 pm Lunch provided
12:45 pm Seminar resumes
2:30 pm Break
4:30 pm Seminar concludes
- Anyone involved in the design of cold formed steel structural members. This seminar will provide a quick and effective means of learning about the 2012 edition of CSA S136 (North American Specification for the Design of Cold-Formed Steel Structural Members).
- Anyone who would like the opportunity to have questions answered concerning all aspects of cold formed steel design.
Speakers
Dr. R.M. Schuster, P.Eng.University of Waterloo
Waterloo, Ontario
General Manager
Canadian Sheet Steel Building Institute
Cambridge, Ontario
Tuesday, 16 September 2014
CSSBI Colleague Thanked for Contribution to the CEE Structures Lab at the University of Waterloo
Dr. Reinhold Schuster, respected colleague of the Canadian Sheet Steel Building Institute was honoured last week at a ceremony at the University of Waterloo Department of Civil and Environmental Engineering (CEE) Structures Laboratory. Dr. Schuster was instrumental in securing the donation of a new 2500 kN portal frame for the CEE Structure Laboratory.
Click here to read the thank you letter from the University to Dr. Schuster.
Tuesday, 9 September 2014
Application of UL Fire Resistance Ratings in Canada
The National Building Code of Canada, Part 3 on Fire Protection, Occupancy Safety and Accessibility, requires the fire resistance ratings for assemblies to be determined on the basis of tests conducted in accordance with CAN/ULC-S101 “Fire Endurance Tests of Building Construction and Materials”. S101 is a Canadian test standard used by agencies like Underwriters’ Laboratories of Canada (ULC) to conduct fire testing of building components. ULC listings have been used by Canadian design professionals for many years to select fire rated building assemblies, but there is another source for listings that significantly increases the available options: these are the Underwriters Laboratories Inc. (UL) tested assemblies.
It was always possible to use the UL listed assemblies in Canada, but questions were raised about the equivalence of the UL tests to the requirements of CAN/ULC-S101, and in particular the impact of UL loads calculated using Allowable Strength Design instead of Limit States Design as required in Canada. To address this difference in design approach, the UL designs included a “load restricted factor” (LRF) to reduce the design load for Canadian applications.
Working with UL and ULC, representatives of the Steel Framing Alliance, Canadian Steel Construction Council and the American Iron and Steel Institute were successful in getting adopted a LRF of unity for load-bearing cold-formed steel wall and floor assemblies listed in UL’s directory. Having no load restriction is possible because the calculation of the member resistance in Canada and the U.S. is based on the same standard: CSA S136-07 or ANSI/AISI S100-07, “North American Specification for the Design of Cold-Formed Steel Structural Members”.
Prior to this development, only assemblies that were ULC rated were readily accepted, and because very few tested assemblies were listed in their directory, cold-formed steel faced a significant barrier to entry into the mid-rise construction segment. With the removal of any load restriction, about 30 UL fire-rated load-bearing wall assemblies can now be used in the Canadian market. This LRF can only be applied to load-bearing wall assemblies tested with laterally braced steel studs which account for the majority of UL listed assemblies. In comparison, a more conservative factor of 0.82 and 0.65 must be applied to wood framed walls and floors respectively.
For More Information from UL
For more detailed information, please refer to UL’s website (www.ul.com) and open “BXUV7.GuideInfo” (on the bottom of their homepage, click on “Certifications”, then entre BXUV7 in the “UL Category Code” box and click search, then click on the “link to file” BXUV7.GuideInfo). For more specific help, contact the Standards and Codes Consultation Services staff at ULC through their website at www.ulc.ca.
Click to download Technical Bulletin Volume 1 Number 3: Application of UL Fire Resistance Ratings in Canada
Thursday, 28 August 2014
Repainting Factory Prefinished Metal Panels
Prefinished sheet steel is used on many building products from wall cladding, to architectural roofing to interior panels. Prefinished sheet steel has been used in Canada for over 30 years and there may be sites were the paint surface is in need of repainting.
Due to the diversity of factory applied prefinished systems, and the diversity of potential field applied repaint systems, it is impossible to offer one comprehensive repaint procedure for all possible situations. However, it is possible to offer a set of guidelines to be considered in every potential situation.
LET COMMON SENSE PREVAIL!
Before You Begin
CONSULT a local, respected professional painter, experienced and equipped to do the job correctly. They can often recommend a coating system for your application that has been proven by experience. Since local environmental conditions can be unique, local experience is valuable.
CONSULT with the original panel fabricator/supplier who can enlist the expertise of the prefinished sheet suppliers to give proven compatible repaint recommendations.
Repaint Procedures
The purpose of every repaint procedure is to prepare the surface to be painted to achieve maximum "recoatability" and intercoat adhesion; that is, to make certain that the new paint sticks to the old surface. Some type of surface cleaning, such as described in CSSBI Sheet Steel Facts #3, should be employed to remove loose surface dirt, chalk, mildew, etc., to facilitate maximum repaint adhesion.
Special attention and treatment must be given to areas that may have already begun to corrode. In those areas, all traces of white, black or red rust must be removed, usually with wire brushing, and primed with a properly formulated corrosion resistant "zinc rich", or similar primer, before repainting with the desired colour coat.
Recoatability Test
To be certain an old surface is ready to accept repainting, it is recommended that a "recoatability test" is run. The following procedure has served the industry well for a number of years:
Quality Paint Means a Quality Job
Remember, typical field-applied air-dry paint finishes usually demonstrate permanence and performance that correspond to their purchase price. Retail house paint applied to a commercial/industrial building will perform like retail house paint and may not give expected performance. The cost of house paint may be lower initially, but because it is not specifically formulated to adhere to metal siding, it will not last nearly as long or perform nearly as well as systems specifically design for repainting sheet steel.
- Clean and otherwise prepare several small test areas representative of the entire surface to be repainted.
- Apply a coat of the desired repaint according to the manufacturer's instructions. Allow each test area to dry according to the manufacturer's instructions.
- After drying, using about 200 mm of gray "duct" tape for each area to be tested, firmly smooth about 75 to 125 mm of the tape onto the repainted areas. Rapidly pull off the tape, attempting to remove the recently applied air-dried coating.
- Unsatisfactory adhesion/compatibility is indicated if the new coating is removed with the tape.
- If an unsatisfactory test occurs, it may be necessary to conduct a different or additional cleaning procedure, apply an intercoat adhesion primer, or select a different type or different manufacturer's repaint coating.
- Repeat the "recoatability test" until satisfactory results are obtained.
Quality Paint Means a Quality Job
Remember, typical field-applied air-dry paint finishes usually demonstrate permanence and performance that correspond to their purchase price. Retail house paint applied to a commercial/industrial building will perform like retail house paint and may not give expected performance. The cost of house paint may be lower initially, but because it is not specifically formulated to adhere to metal siding, it will not last nearly as long or perform nearly as well as systems specifically design for repainting sheet steel.
Thursday, 21 August 2014
Low Slope Steel Roofing - the Winners in Life Cycle Cost Analysis
These are the results of a study conducted by Ducker Research Company1 for the National Roofing Contractors Association (NRCA). The purpose of the study was to compare three commonly used types of low slope roofing systems (2:12 roof slope or less) from the standpoints of service life, maintenance cost, and overall life cycle cost.
The study looked at the following three different roofing types:
- Metal (mostly unpainted coated steel roofs)
- Built Up Roofs (BUR) - modified bitumen, asphalt
- Single ply membrane (EPDM/PVC/TPO)
Four different building categories were surveyed:
Based on 41 plus interviews with building owners and managers, 36 case studies of roofing systems were selected from the western, northern and southern regions of the United States. In all, twelve case studies were evaluated on each of the three roofing types. Steel comprised the vast majority of the metal roofing systems.2 Most of the roofs were installed between 1981 and 1994; roof areas varied from 4,000 to 750,000 square feet with the average being approximately 92,000 square feet. The expected service life of steel roofing was determined to be 40 years – 17 years longer that Built Up Roofs and 20 years longer than Single Ply systems (see Figure 1).
- Office/Bank
- Retail (store, mercantile)
- Manufacturing (industrial, warehouse)
- Institutional (education, healthcare, hotel/motel)
Based on 41 plus interviews with building owners and managers, 36 case studies of roofing systems were selected from the western, northern and southern regions of the United States. In all, twelve case studies were evaluated on each of the three roofing types. Steel comprised the vast majority of the metal roofing systems.2 Most of the roofs were installed between 1981 and 1994; roof areas varied from 4,000 to 750,000 square feet with the average being approximately 92,000 square feet. The expected service life of steel roofing was determined to be 40 years – 17 years longer that Built Up Roofs and 20 years longer than Single Ply systems (see Figure 1).
Life Cycle Cost: All relevant aspects of low-slope roofing were considered: roof design, number of layers, sheet gauge, standing seam or through-fastened, insulation type and thickness, installation systems (i.e. seamed, ballasted, etc.), labour, balance of systems (i.e. venting, parapets, etc.), geographical effects, life span and additional items relating to the full life cycle, as well as the original installation cost.
Steel roofing has two characteristics that the other two roofing materials do not:
- Steel is a non-porous material and under some conditions requires no underlayment to keep the building dry
- Steel is easily engineered to withstand increased gravity and wind loads
Service life, durability and life cycle cost are considered the most important criteria in the selection of roofing type, according to building owners. While the majority of buildings had experienced roof leaks, none of the steel roofs had leaked as a result of material failure. By comparison, 30% of the Built Up Roofs and 56% of the Single Ply roofs experienced leaks resulting from material failure.
Furthermore, owners of buildings having steel roofs reported having little or no regular maintenance performed on their roofs. The leaks reported on steel roofing were a result of contractor installation problems. Regardless of roofing type, failure to achieve a quality installation is the primary reason for roof failure. (see Figures 2 and 3)
The Ducker Research Company study showed that the life cycle cost of a metal roof is significantly less than BUR and Single Ply roofing. Steel roofing had the lowest maintenance costs and had, on average, a 17+ year greater lifespan than the other two roofing systems. The study also concluded that
building owners believe that service life and life cycle costs are the most important factors in roofing material selection and overall, metal roofing is by far the best option based on its lowest life cycle cost. Add to this the fact that steel roofing is 100% recyclable, has industry leading recycled content and easily qualifies for LEED Canada certification.
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