Cas d'étude: L’acier prépeint coloré ajoute un élément visuel intéressant à une école de Terre-Neuve-et-Labrador

Projet: Carbonear Academy

Carbonear, Terre-Neuve et Labrador

La Carbonear Academy, qui a la capacité d’accueillir 470 élèves de la maternelle à la 8e année, a ouvert ses portes en septembre 2013. Même si elle venait tout juste d’être construite, un nombre d’élèves supérieur aux attentes a obligé la province à dépenser 2 millions de dollars supplémentaires pour la construction de quatre salles de cours de plus, laquelle a été achevée au début de l’année. Cette école remplace l’école primaire Davis Elementary, vieille de 60 ans.

L’utilisation de l’acier a permis à l’architecte d’ajouter un élément visuel intéressant à l’aide de revêtement mural aux couleurs primaires vives. « Nous avons utilisé de l’acier, car nous étions soumis aux exigences du propriétaire. Les principales préoccupations étaient la durabilité, la résistance aux intempéries et l’entretien minime », déclare l’architecte Greg Snow de Gibbons Snow Architects Inc. « L’acier permet l’utilisation d’une grande variété de profils et de couleurs. Nous avons utilisé des couleurs vives et différentes textures pour ajouter un élément intéressant. »

Son emplacement présentait quelques défis pour l’équipe, dit Snow, « Elle est construite dans le flanc d’une colline. Si nous avions reculé davantage, l’excavation serait devenue très coûteuse », explique-t-il. « C’est un long site très étroit. Nous avons utilisé des blocs de couleur, ce qui crée une rupture dans la façade et lui donne un élément visuel intéressant. Pour certaines sections autour des fenêtres, nous avons utilisé des profils ondulés ordinaires pour créer une rupture dans la façade. »

L’école mesure 137 m (450 pieds) de long, renfermant un espace utilisable de 5 110 m2 (55 000 pi ca). Construite à l’aide d’acier de construction et munie de murs en maçonnerie et de revêtements muraux en acier galvanisé prépeint, elle est faite pour durer. « C’est un monument très visible. Il instaure un sens de permanence dans la collectivité », déclare Snow. L’école a été construite selon les normes les plus sévères en matière d’efficacité et d’environnement, et l’architecte a pu tirer profit de certains éléments verts de l’école de façon à engager les élèves et à leur enseigner la réduction de consommation d’énergie. Les personnes qui ont visité le complexe ont été impressionnées par l’extérieur coloré, le stationnement et les voies d’accès habilement conçus, les salles de classe spacieuses et le gymnase d’une certaine ampleur.

« Nous avons incorporé un logiciel interactif lié aux systèmes du bâtiment afin de permettre aux élèves d’observer les systèmes mécaniques et électriques de l’école en temps réel. Ils peuvent constater l’utilisation d’énergie et la comparer à celle d’autres écoles », dit Snow. « Certains professeurs s’intéressent beaucoup à la possibilité de l’utiliser comme outil d’enseignement de la réduction de consommation d’énergie. » Les caractéristiques éco-énergétiques du bâtiment comprennent l’éclairage à haute efficacité muni de capteurs de lumière du jour, ainsi que le chauffage et le refroidissement géothermiques.

Un long panneau d’alliage de couleur jaune a été utilisé pour l’auvent devant le bâtiment afin d’ajouter un élément visuel intéressant supplémentaire et une protection contre les intempéries. À l’intérieur de l’école, la couleur jaune a encore une fois été utilisée pour les escaliers en métal ondulé. « Le hall et l’entrée constituent un véritable point central du bâtiment », déclare Snow. « Nous avons utilisé certaines couleurs personnalisées. »

ÉQUIPE DE CONCEPTION ET DE CONSTRUCTION
ARCHITECTE : Gibbons + Snow Architects Inc.
ENTREPRENEUR GÉNÉRAL : Marco Group
ENTREPRENEUR DE PAREMENT MÉTALLIQUE : Hampton Building Systems Inc.
FOURNISSEUR DE PAREMENT MÉTALLIQUE : Agway Metals Inc. 
ENTREPRENEUR DE CHARPENTES MÉTALLIQUES LÉGÈRES ET DE CLOISONS SÈCHES : CAD Construction
FOURNISSEUR DE CHARPENTES MÉTALLIQUES LÉGÈRES : Imperial Group
PHOTOGRAPHIE : Stephen Sheppard

Cliquez pour télécharger le cas d'étude #85-14: L’acier prépeint coloré ajoute un élément visuel intéressant à une école de Terre-Neuve-et-Labrador

Project Profile: Colourful prepainted steel adds visual interest to new school in Newfoundland and Labrador

Project: Carbonear Academy

Location: Cabonear, Newfoundland

The Carbonear Academy, which has the capacity for 470 students from Kindergarten to Grade 8, opened for classes in September 2013. Although just completed, a higher than expected number of students forced the Province to spend an additional $2 million on the construction of four additional classrooms which were completed early this year. The school replaces the 60-year-old Davis Elementary School.

Using steel allowed the architect to add visual interest to the school with horizontal cladding in bright primary colours. “We used steel because we were driven by the owner’s requirements. The main concerns were durability, weather-ability and low maintenance,” says architect Greg Snow of Gibbons Snow Architects Inc. “With steel there are a wide variety of profiles and colours you can use. We used bright colours and different textures to add interest.”

The school’s location posed a bit of a challenge for the crew, Snow says, “It is built into the side of a hill. If we had gone back any farther, the excavation would have become very expensive,” he explains. “It’s a very narrow, long site. We used blocks of colour, which breaks up the elevation and gives it a visual interest. For some sections around the windows, we used regular corrugated profiles to break up the elevation.”

The building is 137m (450 ft.) long and has 5,110m2 (55,000 sq. ft.) of useable space inside. Constructed of structural steel, with pre-painted galvanized steel cladding and masonry walls, it was built to last. “It is a very visible landmark and it has a sense of permanence in the community,” says Snow. The school has been built to the highest possible efficiency and environmental standards and the architect was able to take advantage of some of the school’s green elements in a way that will engage students and teach them about energy consumption. Visitors touring the complex were very impressed by the colourful exterior, neatly designed access lanes and parking, the spacious classrooms and sizeable gymnasium.

“We incorporated interactive computer software tied into the building’s systems so students can see the mechanical and electrical systems of the school in real time. They can see the energy usage and compare it to other schools.” Snow says. “Some of the teachers are quite interested in using it as a teaching tool for energy consumption.” The building’s energy conscious features include higher efficiency lights with daylight sensors and geo-exchange heating and cooling.

A long yellow composite panel was used for the canopy in front of the building to add further visual interest and some weather protection. Inside the school, the yellow colour was again used for the corrugated metal stairs. “The lobby and entrance area are a real focal point for the building,” says Snow. “We used some custom colours.”

DESIGN AND CONSTRUCTION TEAM 

ARCHITECT: Gibbons + Snow Architects Inc. 

GENERAL CONTRACTOR: Marco Group 

STEEL SIDING CONTRACTOR: Hampton Building Systems Inc. 

STEEL SIDING SUPPLER: Agway Metals Inc. 

LIGHT STEEL FRAMING/ DRYWALL CONTRACTOR: CAD Construction 

LIGHT STEEL FRAMING SUPPLIER: Imperial Manufacturing Group 

PHOTOGRAPHY: Stephen Sheppard

Click to download Case Study #85-14: Colourful prepainted steel adds visual interest to new school in Newfoundland and Labrador

Daily Commercial News Article - Does LEED v4 provide a better deal for steel?

Daily Commercial News published an article on February 11, 2016 titled Does LEED v4 provide a better deal for steel? which details the sections and credits in the newest version of LEED v4 for New Construction and Major Renovations and the ways that steel can earn points towards certification.

From the article, 

Under LEED for New Construction and Major Renovations (v4), there are five MR credits available for many steel products, for a total possible 13 LEED points:

• Building life-cycle impact reduction (up to five points) 

• Building product disclosure and optimization — environmental product declarations (up to two points) 

• Building product disclosure and optimization — sourcing of raw materials (up to two points) 

• Building product disclosure and optimization — material ingredients (up to two points) 

• Construction and demolition waste management (up to two points).

 The CSSBI is in the process of finalizing its industry average Environmental Product Declaration (EPD) for steel roofing, cladding and decking products and it will be available early 2016.

Mark Thimons, vice-president of the Steel Recycling Institute also mentions in the article that steel can play a role in credits relating to recycled content and urban heat-island effect.

Click to read the full article and learn about the ways steel and LEED v4 can work together for a more sustainable built environment.

Which is the more sustainable building material - wood or steel? MYTH #3

According to certain “studies,” wood claims a smaller environmental footprint than any other major building material. However, a closer look at the facts reveals some significant inconsistencies with that claim.

This is week 3 of 4 where we will feature a myth about the sustainability of wood vs. steel. See here for past 2 myths #1 and #2.

MYTH: Wood is more sustainable than steel because wood construction products store carbon. 

REALITY: Carbon storage for construction products is temporary, only shifting impacts to future generations. 

• Carbon is sequestered in the fiber of trees, but that does not mean that wood buildings become large reservoirs of carbon that is stored indefinitely. Upon harvesting, the unused root and leaf systems immediately return their CO2 to the atmosphere by decay. For wood products, the reality is that carbon storage is also temporary and it is released back into the atmosphere at the end of the wood building’s life either by the demolition and subsequent decay of the wood or by incineration. 
• Ann Ingerson of The Wilderness Society states: “As a result of wood waste and decomposition, the carbon stored long-term in harvested wood products may be a small proportion of that originally stored in the standing trees―across the United States, approximately 1 percent may remain in products in use and 13 percent in landfills at 100 years post-harvest.”(1)

If you want to learn about the other myths, you can download the Steel Market Development Institute's Fact Sheet to learn more.

(1) Ingerson, Ann, “Carbon Storage Potential of Harvested Wood: Summary and Policy Implications,” The Wilderness Society, October 23, 2010, p. 1.

Which is the more sustainable building material - wood or steel? MYTH #1

According to certain “studies,” wood claims a smaller environmental footprint than any other major building material. However, a closer look at the facts reveals some significant inconsistencies with that claim.

Each week for the next 4 weeks we will feature a new myth about the sustainability of wood vs. steel.

MYTH: Studies demonstrate that wood is a more sustainable material than steel. 

REALITY: The most-cited study contained numerous incorrect assumptions about steel, and it omitted wood impacts.

• A study cited often by the wood industry was published by the Consortium for Research on Renewable Industrial Materials (CORRIM) and is based on outdated information. For example, it made incorrect assumptions about the quantity of steel needed for its comparisons.
• Wood is typically a single-use material. At the end of its life, a building’s wood frame is typically landfilled or incinerated. This returns any stored carbon dioxide back into the atmosphere as either carbon dioxide or methane, shifting greenhouse gas burdens to future generations. 
• In comparison, steel is the world’s most recycled material. Steel construction products have a recycling rate of more than 90 percent, meaning that at the end of a steel building’s life, more than 90 percent of its steel is recycled into another steel product, using significantly less energy than was necessary to create the original product. A material that can be recycled continually over centuries with no loss in quality and that lowers the burden on future generations is the very definition of sustainability!

If you just can't wait to see what the other myths will be, you can download the Steel Market Development Institute's Fact Sheet to learn more.

Steel allows house to also be a sculpture

Original Article posted on Domain on October 20, 2015
Click to go to full article - Grand Designs steel house throws away the rule book

Scottish-born Sydney-based advertising creative Scott Lawrie, who has a fine arts background, drew his architectural inspiration from a sculpture by Gemma Smith.

Lawrie says he liked the way the form of the sculpture changed as he walked around it.

“I thought, what if I could get a house that looked like this – a house that would change as you walked around,” he says.

He told me the roof and walls would all be metal and that’s when it became a piece of sculpture. - Owner, Scott Lawrie

“I told Paul to make me nervous when he came back with the designs, and he did. But then he told me the roof and walls would all be metal and that’s when it became a piece of sculpture.”

Clarke’s design wrapped the roof and sides of the steel-framed house in stainless steel, while providing a dark-stained cedar front entry and a fully glazed wall and sliding doors at the rear to maximise the view.

The unconventional shape created the third drama – the challenge of a build where no angles were regular, the walls sloped and nothing was square. Because the house needed to be strong enough to withstand gale-force winds, almost four tonnes of steel was required for the framing.

Click to go to full article - Grand Designs steel house throws away the rule book

New Publication - Serviceability Design Criteria for Low Rise Steel Building Systems

Serviceability is an important aspect of design. It is only eclipsed by design for strength which is paramount. Design for serviceability addresses the performance of the structure with respect to its use, its interaction with non-structural elements and maintenance.

According to NBC 2010, Part 4, Structural Design, Sentence 4.1.3.4. (1), a building and its structural components shall be checked for serviceability limit states (SLS) as defined in Clause 4.1.3.1. (1)(a) under the effect of service loads for serviceability criteria specified or recommended in Articles 4.1.3.5. and 4.1.3.6. and in the standards listed in Section 4.3.

The National Building Code lists four areas of consideration when sizing structural members for serviceability limit states (SLS):

1. the intended use of the building or member;
2. limiting damage to non-structural members made of materials whose physical properties are known at the time of design;
3. limiting damage to the structure itself;
4. creep, shrinkage, temperature changes and pre-stress.

Download our CSSBI B15B-15 Serviceability Design Criteria for Low Rise Steel Building Systems to learn more about how to design for serviceability using a steel building system.

Cement, steel oppose taller wood buildings

The province of Quebec has recently changed Building Codes to allow for taller wood structures. It is the opinion of the steel and cement industries that this change has real potential to negatively affect the public's safety and unfairly favours the wood industry in Quebec over the many steel and cement companies operating in Quebec and contributing to the economy there.

Below is an excerpt from an article from the Cambridge Times posted on August 19, 2015.

MONTREAL - Canada's cement and steel sectors say Quebec is favouring one industry and possibly putting public safety at risk by allowing wood to be used in the construction of buildings up to 12 storeys high.

The Cement Association of Canada said Wednesday that the province's new guide for the construction of taller wood buildings is primarily aimed at supporting Canada's forest industry.
"The government has a duty to protect the health of its citizens, not that of a particular industry," said association president Michael McSweeney.

The association added that the use of cross-laminated timber building systems is no more environmentally friendly than other building systems already recognized in the code, when considering the full life cycle of a building.

Hellen Christodoulou, Quebec regional director of Canadian Institute of Steel Construction, added that not enough research has been completed to ensure the safety of taller wooden buildings.
"The government has not studied this well. It's just a political move and it's problematic," she said in an interview.

Christodoulou added that the wood sector receives heavy subsidies not shared with the concrete and steel industries, which contribute substantially to the economy through taxes and jobs.

Click here to read the full article.

The Canadian Institute of Steel Construction (CISC) has also created a webpage with links to many other articles on this subject.

Fixation de toiture et parement en tôle d’acier prépeinte

Introduction 

Les toitures et les parements (revêtements) en tôle d’acier sont offerts dans une grande variété de profils, de couleurs et de systèmes de peinture. Les systèmes prépeints modernes utilisés sur des produits canadiens fourniront des décennies de bon rendement avant de montrer des signes visibles de détérioration de la surface peinte. Cependant, un composant important du système de parement, c’est l’attache utilisée pour le fixer sur la structure. Cette attache n’est pas seulement une vis; elle fait partie de l’assemblage du toit ou du mur et on doit s’attendre à ce qu’elle fournisse le même rendement à long terme. Ce rendement n’est pas simplement la capacité de garder le parement de façon sécuritaire en place, mais il doit également correspondre à la couleur et la durabilité de la peinture. 

La sélection de la vis appropriée au travail est la première étape de la création d’un système de parement qui fournira un rendement à long terme. L’étape suivante, c’est l’installation. L’installation de vis dans un parement en tôle d’acier est chose courante et peut être fait très de manière efficiente. Les fabricants d’outils ont développé une vaste gamme d’options pour les attaches d’installation dans n’importe quel type d’infrastructure. Le choix de l’outil le plus approprié aidera lors du processus d’installation. Malheureusement, il est possible d’endommager la peinture sur la vis lors de l’installation, comme montré dans la photo ci-dessous. 

Effet du type d’outil d’installation sur une tête de vis 

Un projet de recherche a été mené pour l’ICTAB pour étudier le rendement d’outils d’utilité courante utilisés pour installer des vis qui retiennent un parement sur une ossature en bois. L’objectif était d’évaluer l’outil privilégié pour tenir la tête de la vis peinte durant l’installation. L’étude ne portait pas sur l’évaluation de différents finis (p. ex., peinture en poudre, peinture fraîche ou peinture organique) ni sur l’évaluation de différentes marques d’outils. L’étude a porté seulement sur l’effet que les différents mécanismes d’outil (p. ex., rotation, percussion, chocs ou combinaison) avaient sur la vis durant le processus d’installation. 

Cinq types d’outils ont été testés : 

1. Tournevis électrique avec mandrin à profondeur réglable 
2. Perceuse à percussion à batterie 
3. Tournevis à batterie avec commande du couple réglable 
4. Tournevis/perceuse électrique 
5. Tournevis à chocs à batterie

Les tests suivants ont été effectués :

1. Maîtrise (vitesse) d’installation des outils 
2. Choc (dommage) à cause des outils sur la protection contre la rouille - Accéléré 
3. Choc (dommage) à cause des outils sur la protection contre la rouille - Normal 
4. Protection contre la rouille des vis jamais installée 

Le problème en réalité consiste à trouver le bon équilibre entre le dommage potentiel causé à la tête de la vis peinte et la vitesse d’installation. L’évaluation des données du test était fondé sur une pondération 70/30 de la réduction des dommages et du temps d’installation respectivement. À l’aide de ce critère de sélection, les premiers choix ont été le tournevis électrique avec mandrin à profondeur réglable et le tournevis/la perceuse électrique. Les pires choix ont été la perceuse à choc et le tournevis à choc. 

Quels que soient les critères d’évaluation, le tournevis à chocs était toujours nettement le pire. Les forces de choc agissant sur la tête de la vis endommageront la surface de la vis et causeront une corrosion précoce. Même si les tests ont été réalisés sur des têtes de vis peintes, les mêmes conclusions s’appliquent également aux vis à tête non peinte et en nylon. 

Outils recommandés et méthodes d’installation 

Tournevis 

Les attaches pour toiture et parement en tôle d’acier prépeinte doivent avoir une tête de forme hexagonale. L’outil d’installation comprend un tournevis adapté au format et à la forme de la tête de vis. Souvent, ce tournevis comprend un aimant encastré pour retenir la vis en place durant l’installation. Le fait de passer la vis au travers de la tôle d’acier rejettera les limailles d’acier qui peuvent s’accumuler sur l’aimant du tournevis. Ces limailles doivent être enlevées régulièrement afin que la tête de la vis s’emboîte fermement dans la douille du tournevis. Les tournevis s’usent rapidement et doivent être remplacés après avoir vissé 5000 vis. 

Vitesse de pistolet à vis

Que vous utilisiez une vis autoperceuse ou une vis autotaraudeuse, la vitesse (tr/min) du pistolet à vis est importante. Des vitesses plus basses de pistolet à vis amélioreront le rendement du perçage en réduisant la chaleur générée durant le processus de perçage. Pour fixer du parement en tôle d’acier dans des conditions de métal sur métal ou de métal sur bois avec des vis en acier au carbone, la vitesse maximale recommandée est de 2500 tr/min, Des vitesses plus basses peuvent être souhaitables pour percer dans des éléments plus épais ou avec des vis en acier inoxydable. Le fabricant des vis devrait être consulté. 

Serrage des attaches 

Les attaches exposées pour les systèmes de parement en tôle d’acier comprennent une rondelle sous la tête de la vis pour former un joint étanche. Il est très important que les attaches soient serrées adéquatement afin d’obtenir une étanchéité optimale. Assurez-vous que la rondelle soit comprimée, mais pas jusqu’au point où elle ressortira des côtés de la tête de la vis. Le fabricant des vis devrait être consulté. 

Conclusion 

Les installateurs de parement en tôle d’acier doivent examiner leur choix de pistolet à vis et l’effet qu’il peut avoir sur le rendement à long terme du revêtement de la tête de la vis. L’objectif, c’est de créer un assemblage de toiture et de mur durable, et ceci comprend les attaches. Contribuez à maintenir la qualité des attaches en utilisant un tournevis/une perceuse et non pas un outil qui met la vis en place par des chocs. Soyez également conscient de la vitesse d’installation et de la compression appropriée de la rondelle.

Cliquez pour télécharger Quelques mots sur la tôle d'acier #42: Fixation de toiture et parement en tôle d’acier prépeinte

Fastening Prepainted Sheet Steel Roofing and Siding

Introduction
Sheet steel roofing and siding (cladding) is available in a wide variety of profiles, colours and paint systems. The modern prepainted systems used on Canadian-made products will provide decades of beautiful performance before there are any visible signs of deterioration of the paint surface. However, an important component of the cladding system is the fastener used to attach it to the structure. This fastener is not simply a screw; it is part of the roof or wall assembly and should be expected to provide the same long-term performance. This performance is not simply the capacity to safely hold the cladding in place, but also to match the colour and durability of the paint system.

The selection of the correct screw for the job is the first step in the creation of a cladding system that will provide long-term performance. The next step is the installation. Installing screws in sheet steel cladding is commonplace and can be done very efficiently. The tool manufacturers have developed a wide range of options for installing fasteners into any type of substrate. Selecting the most appropriate tool will help the installation process. Unfortunately it is possible to damage the paint coating on the screw during installation, as shown in the photo below.



Effect of Installation Tool Type on Screw Head
A research project was carried out for the CSSBI to investigate the performance of commonly available tools used to install screws attaching sheet steel cladding to a wood frame. The objective was to assess the preferred tool for maintaining the painted screw head during installation. This study was neither an assessment of different finishes (i.e. powder paint, wet paint or organic paint) nor an assessment of different tool brands. This study only looked at the effect the different tool mechanisms (i.e. rotation, hammer, impact or a combination) had on the screw during the installation process.

Five types of tools were tested:

1. Electrical screw driver with depth adjustable nosepiece 
2. Battery driven hammer drill 
3. Battery driven screw driver with adjustable torque control 
4. Electrical screw drill/driver 
5. Battery driven impact driver 

The following tests were performed:

1. Installation proficiency (speed) of tools 
2. Impact (damage) by tools on rust protection – Accelerated 
3. Impact (damage) by tools on rust protection – Normal 
4. Rust protection of screws never installed 

The real-life problem is to find the right balance between the potential damage inflicted on the painted screw head and the installation speed. The evaluation of the test data was based on a 70/30 weighting of minimizing damage and reducing installation time respectively. Using this selection criterion the first choices were the electrical screw driver with depth adjustable nose piece and the electrical screw drill/driver. The poorest choices were the hammer drill and impact driver.

No matter the evaluation criteria, the impact driver was always significantly the worst performer. The impact forces acting on the screw head will damage the screw surface and lead to early corrosion. While the tests were done on painted screw heads, the same conclusions would apply to unpainted and nylon head screws as well.

Recommended Tools and Installation Methods
Drivers
Fasteners for prepainted sheet steel roofing and siding will have a hexagonal shaped head. The installation tool incorporates a driver that matches the size and shape of the screw head. Often these drivers include a recessed magnet to hold the screw in place during installation. The act of driving the screw through the sheet steel will release steel filings that can accumulate on the driver magnet. These filings need to be removed on a regular basis so that screw head fits snugly into the driver socket. Drivers will also wear out with use and should be replaced after driving 5,000 screws.



Screw Gun Speed
Whether using a self-drilling or self-tapping screw, the screw gun speed (RPM) is important. Slower screw gun speeds will improve the drilling performance by reducing the heat that is generated during the drilling process. For fastening sheet steel cladding in metal-to-metal or metal to-wood conditions with carbon steel screws the maximum RPM recommended is 2500. Slower speeds may be advisable for drilling into thicker steel members or with stainless steel screws. The screw manufacturer should be consulted.

Tightening the Fastener
Exposed fasteners for sheet steel cladding systems will include a washer under the head to make a water-tight seal. It is important that the fasteners be tightened correctly to obtain the optimum seal. Make sure the washer is compressed, but not so much that it is squeezed out the sides of the screw head. The screw manufacturer should be consulted.



Conclusion
The installers of sheet steel cladding need to consider their choice of screw gun and the effect it can have on the long-term performance of the screw head coating. The objective is to create a long-lasting roof or wall assembly, and this includes the fasteners. Help maintain the integrity of the fasteners by using a screw drill/driver and not a tool that drives the screw by impacting it. Also be cognizant of the best installation speed and properly compressing the washer.

Click to download CSSBI Fact Sheet #42: Fastening Prepainted Sheet Steel Roofing and Siding

The Steel vs. Wood Debate

With the recent changes to the Ontario Building code allowing combustible construction materials for buildings up to 6 storeys high, there is a lot of information out there speaking about the various benefits and disadvantages of materials like concrete, wood and steel.

The Multi-Housing News Online posted an article last week Why Cold Formed Steel is a Viable Alternative to Wood Frame Construction written by Charles Specht, CIC, CDA, Constructive Risk.

In this article Charles writes about some of the major fires that occurred in 2014 in the United States at various wood framed building projects. He uses these examples to discuss the impact of building material choices on things like the cost of Builders Risk Insurance.

Insurers have long been wise to these risks. “Wood” construction has a greater likelihood to burn or be damaged by fire and will be a total loss versus a partial one. Loss history for wood construction has been poor, and carriers are very restrictive of the amount of risk they will take. This drives up the cost to the builder, and actually weakens the pro-wood argument that it is less expensive than other materials. The recent major wood frame fires calls for a need to look at cost savings and particularly insurance more closely.

He says in the article that steel framing is a viable alternative to wood framed construction as it is inherently non combustible and can qualify for lower Builders Risk Insurance costs. He also talks about the other benefits of steel framing such as durability, moisture- and mold-resistance and recyclability.

Click here to read the whole article and visit the CSSBI website to download all the resources and information you need to design and build in cold formed steel framing.

Galvanic Compatibility of Galvanized Steel and Aluminum

In many practical construction applications the contact of dissimilar materials is sometimes unavoidable. When dissimilar metals are in contact with one another in the right medium the condition is called Galvanic Coupling. The effects of galvanic coupling depend on how different the electrochemical properties of the metals are. The following Technical Bulletin describes the compatibility of Galvanized steel and Aluminum, two materials commonly found together in the construction of lightgauge steel framed homes. Dr. X.G. Zhang is a Corrosion Scientist for Cominco Ltd., and is author of Corrosion and Electrochemistry of Zinc.

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. 

Click to download Technical Bulletin Volume 2, Number 2: Galvanic Compatibility of Galvanized Steel and Aluminum

Natural Finish Metallic Coatings – Attractive but not Architectural

Variations in Surface Appearance Caused by Viewing Angle

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Architects and Specification Writers are increasingly selecting unpainted metallic coated steels for architectural roofing and cladding applications on building exteriors where they want a “Silver” metallic finish. This is occurring more frequently, and even on “prestige” type projects. The Canadian Sheet Steel Building Institute whose fabricator members manufacture a wide variety of building panel profiles for roofing and cladding applications, are being asked to supply unpainted (natural finish) galvanized or resin coated 55% Aluminum-Zinc coated steel for these architecturally exposed end uses. Oftentimes, these materials are specified because the designer finds the natural finish of these products very appealing and sometimes because of material cost savings opportunities.

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