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An I-joist consists of two parallel chords made from joined structural 2" x 3" and 2" x 4" timber or composite wood (LVL, LSL). The chords are connected together by a web made from 3/8" or 7/16" OSB panels.
These products are available in stock at the most common heights of 9½", 11⅞", 14" and 16". Some manufacturers produce joists up to 24" in height.
The main advantage of these products is that they can be cut on-site to the exact dimensions required. They can also be used in continuous spans in order to speed up installation. The web can be drilled in accordance with the manufacturer’s instructions in order to allow ducts and conduits to pass through, especially in the central section of spans where the shear load is weakest.
These types of joists are the least costly and are overseen by an external inspection company (e.g.: APA)
Open web joists with metal connector plates
These are triangular joists that consist of two parallel chords made from 2" x 3" and 2" x 4" timber laid flat with the web components made from wooden struts the same width as the chords. The elements that make up the chords are first joined mechanically on the wide face with metal connector plates. The struts and chords are then assembled in rigid templates, with metal connector plates mechanically pressed into the narrow face of the components.
The final product provides for a large support surface for installing floor coverings while allowing for the passage of the various conduits and ducts without cutting the components of the web.
Open web joists are available in two formats: Those that are produced to the exact dimensions for each project, and in-stock trusses with adjustable ends (generally adjustable up to 12’’ on each end).
These joists are usually used as single spans, and can be supported on a beam or a wall by the upper chord, which is often doubled at this end.
Open web joists with metal struts
These joists are essentially produced using the same technique as for open web joists with metal connector plates, except that the wooden web components are replaced by metal struts that are marketed under the names SpaceJoistTM or PosiSTRUTTM. These are produced using thin galvanized steel sheets.
The V-shaped struts feature a nearly tubular section at the end in order to resist lateral buckling. The height of the joists is predetermined by the selection of metal components, namely 9¼", 11¼", 11?", 12¾", 14" and 16".
These joists are available in two formats: Those that are produced to the exact dimensions for each project, and in-stock joists with adjustable ends (generally adjustable up to 12’’ on each end).
In conclusion, the selection of the type of joist is entirely up to you. However, your final choice should be based on this type of product and not on timber. Engineered wood joists provide an enhanced support surface and better spans, and they use less wood material during production than the 2" x 8", 2" x 10" or 2" x 12" timber joists that were used in the past.
Laminated Veneer Lumber (LVL)
LVL is made from veneers that are combined in such a way as to emulate the natural characteristics of wood. Panels with the layers aligned are used in order to allow the strands of the veneers to remain parallel to the main direction. These products are generally used as posts, beams and lintels.
The manufacturing process allows for approximately 75% of the tree to be converted to structural elements, which represents an increase of approximately 30% compared to timber processing.
The panels, which are usually 1-¾" thick, are split into widths of 9-½" to 24" at lengths from 8' to 66'. The beams and columns usually include between 2 and 4 layers of 1-¾" that are nailed, screwed and/or bolted together. Some manufacturers produce thicknesses of up to 7".
LVL wood is often identified by its modulus of elasticity (rate of deformation), which generally varies from 12,400 MPa (1.8E) to 13,790 MPa (2.0E).
Parallel Strand Lumber (PSL)
PSL is made from long cuts of up to ¼" in thickness with an average length of at least 300 times its thickness, all glued together in parallel and pressed to form continuous elements. This type of material is resistant, attractive and often left as is. It is primarily used for posts, main beams and large-span lintels.
In addition to the normal 1-¾" width of LVL wood, PSL is also available in widths of 3 ½", 5-¼" and 7” and heights of 9-½’’ to 18-¾’’. The most common modulus of elasticity is 13,790 MPa (2.0E). However, columns use a modulus of 1.8E.
This product provides enhanced resistance to mechanical shear and transverse stress, along with excellent flexibility. Parallam™ is the only PSL product available on the market at the present time.
Laminated Strand Lumber (LSL)
LSL is made from long cuts of up to 1/10" in thickness with an average length of at least 150 times its thickness, all glued together in parallel and pressed to form continuous elements. This is an intermediate product that falls between LVL and PSL wood.
It is recut in order to assemble supplementary structural elements such as ledger boards and medium-span beams or lintels.
This product is also used as studs for very high walls. Highly resistant to bending, shear and transversal and longitudinal compression, it provides a higher resistance/weight ratio than steel.
The modulus of elasticity that is available varies from 9,000 to 10,700 MPa (1.3E to 1.55E). LSL is produced in a variety of widths, including 1-¼", 1-¾" and 3-½", at heights from 9-¼" to 20". TimberStrand™ is the only LSL product available on the market at the present time.
Glulam wood is comprised of a stack of planed and prejointed wood pieces measuring between 2" x 3" to 2" x 12", that are then glued together under pressure using water repellant adhesives, and combines esthetics with structural properties. It lends itself to large straight or curved sections with greater stability than large timber pieces.
Glulam wood is used for beams, columns or arches in lengths that are limited primarily by transportation considerations. Depending on the supplier, it is available with varying finishes ranging from regular planed (Industrial) to architectural finish (Quality) that is ready for the finishing coat.
It is generally accepted that glulam wood pieces have the same physical characteristics as the wood that went into their manufacturing. From a mechanical perspective, the categorization of glulam wood is directly related to that of the layers of timber that it consists of. Resistance categorization varies according to use. Exterior layers of Laminated Veneer Lumber (LVL) can be added to categories 2.0E to 2.4E in order to enhance the flexibility.
Ledger board is made from construction lumber or engineered wood, and frames the outside of the floor.
It serves as bracing for the floor joists and trusses. It is also involved in the transfer of vertical loads from the higher levels. In terms of thickness, ledger board is 1-½" thick when made of construction lumber, 1-?" thick when made of OSB panels and 1-¼" thick when made of composite structural timber panels (LVL, LSL or PSL).
Nailing the subfloor panels to the ledger board creates a diaphragm effect for the entire structure.
Galvanized steel hanger
A variety of accessories and hangers are available for the various types of connections required for lumber or engineered wood. They are mass produced and cold formed using thin sheets of galvanized steel. They have holes for nails or wood screws (e.g.: StrongDriveTM, from Simpson Strong Tie).
Their final capacity for transferring lateral loads must be determined by testing in accordance with standard ASTM D1761. The results of these tests must be interpreted in accordance with Section 10.10.3.1 of standard CSA O86 in order to determine the weighted resistance for each assembly. It is very important to ensure that the proper hanger is used for each type of connection.
These hangers are primarily used for light framing, but can sometimes be used in beam and post systems consisting of medium-width wood. They allow for the transfer of heavy loads, both on the sides and tops of beams and on the top and base of columns. In cases where they will be continually exposed to the weather and use with treated wood products that use corrosive preservatives, it is crucial to select products that have a thicker galvanized coating.
This adhesive, which comes in a cartridge, is used to attach panel coverings to support elements such as floor joists. Urethane-based products do not shrink as they dry. They are resistant to moisture and do not require perfectly smooth surfaces. They do not release any toxic vapours as they dry, so they can be used indoors and for repairs.
This adhesive, which comes in a cartridge, is used to attach panel coverings to support elements such as floor joists. Solvent-based products do not require perfectly smooth surfaces, but they may shrink as they dry. In addition, they are slightly less resistant to moisture than urethane adhesives. They also release toxic vapours as they dry, so they should only be used outdoors. This type of adhesive is more liquid, and therefore, is easier to apply at the worksite, especially in colder weather.
Why choose ecological construction/renovation?
The main reasons for choosing eco-design include the reduction of your environmental impact, health enhancement and the decrease of your energy and water consumption. It is important to note that three main themes are a recurring part of the equation:
Is eco-design complicated? No, exactly the opposite!
Basic principles for all projects:
Even though construction/renovation projects can improve your quality of life, they also have a significant impact on the environment. Did you know…
The concentration of volatile organic compounds (VOC), which are chemical products that are hazardous to health, is 2 to 5 times higher inside the home than outside, both in the city and the country? This concentration can even be 1,000 times higher following certain types of renovations, especially painting.
The residential sector is responsible for 30% of all greenhouse gases produced in the country. A large percentage of these emissions come from the consumption of energy, primarily in the form of heating (62%), water heaters (19%), operating household appliances (13%), lighting (4%) and air conditioning (2%)
Canadians are among the largest water consumers in the world, with an average household consumption of 329 litres per day, more than double that of the average household in France, which consumes150 litres per day
The construction and renovation sector generates significant quantities of waste materials created during preparation or construction sites (including demolition), losses on cut or damaged materials, temporary-use products and packaging.
There are many other benefits to choosing ecological construction/renovation. For example, installing electronic thermostats reduces your energy consumption and enhances your comfort. In addition, VOC-free floor coverings, counters and paint reduce smog and significantly improve the quality of indoor air. Nevertheless, there are still a number of myths surrounding ecological construction/renovation. Here are the main ones:
Ecological construction/renovation is more complicated!
There are more and more easy-to-use ecological materials available at renovation centres. It is no more complicated to install a low-flow toilet, a VOC-free floor covering or Energy Star® windows than to install less ecological versions! On the other hand, there are some systems that are more complex, such as gray water recovery or solar heating. However, experts are available to guide you and assist you with your projects.
Ecological options are more expensive!
Energy savings, the increased value of your home and subsidies available in certain provinces reduce the actual costs of installing ecological options, especially in the case of more complex systems. For example, a LEED certified home costs approximately 8% to 10% more to build than a regular home, but it will save 25% on your energy bill, which more than offsets the higher initial cost. The costs for other products, such as paints, VOC-free floor coverings or low-flow toilets, are now competitive with traditional options. According to a recent survey, 72% of Canadians would be willing to pay more for a more ecologically sound house.
Ecological construction is a trend that will fade away!
Nothing could be further from the truth! Human beings have always used natural local resources to their advantage, including the position of the sun and the prevailing winds. These practices are even more important today, in the face of higher energy costs, the depletion of resources and climate change. An increasing number of scientific studies also show that certain materials cause health risks when used inside the home.The growing number of LEED® (Leadership in Energy and Environmental Design) certified buildings in Canada, and the ever increasing availability of ecological products of low chemical content is evidence of a healthier and more ecological future in construction. The most performing houses also have a greater resale value besides becoming very much in demand on the real estate market