Presentation on theme: "Engineered Floor and Roof I-Joists I-joists are composed of two horizontal components called flanges and a vertical component called a web. Wood I-joists."— Presentation transcript:
Engineered Floor and Roof I-Joists I-joists are composed of two horizontal components called flanges and a vertical component called a web. Wood I-joists are used as a framing material primarily in floors, but may also be used as roof rafters where long length and high load capacity are required.
I-Joist Components Flanges are manufactured from end-joined, solid sawn lumber or structural composite lumber (SCL), while webs typically consist of oriented strand board (OSB). I-joists are glued together with adhesives continuously along their length. The entire assembly is dependent on the strength of the glue and joist hangers.
Types of I-Joists This photo shows I-joists with a plywood web and sawn-lumber flanges. This combination of materials was common in the 1980s.
Types of I-Joists This photo shows I-joists with a oriented strand board (OSB) web and structural composite flanges such as laminated veneer lumber (LVL) or laminated structural lumber (LSL). This combination of materials arrived in the 1990s.
Lumber used to produce I-Joists Structural composite lumber (SCL), which includes laminated veneer lumber (LVL), laminated strand lumber (LSL) and oriented strand lumber (OSL), is a family of engineered wood products created by layering dried and graded wood veneers or flakes with waterproof adhesive into blocks of material known as billets. Cured in a controlled process, SCL is typically available in various thicknesses and widths and is easily worked in the field using conventional construction tools.
Structural composite lumber OSB is made with layers of thin, rectangular strands or flakes of wood that are produced by feeding freshly cut hardwood or softwood logs through a cutting machine called a strander. Strands are then dried and blended with adhesives.
Structural composite lumber LVL is built up of layers of veneer that are rotary-peeled from logs. These layers of veneer are coated with high-strength glue and stacked in a large billet to the desired length, width, and thickness. Usually, the grain in all of the layers is parallel. The LVL billet is cured in a heated press, which brings it to its final thickness and sets the glue.
Structural composite lumber LSL is made by reducing logs from fast-growing trees to thin strands up to 12 inches long which are bonded with adhesive to create a billet (large block).
I-Joist hangers Check the nail holes in the hangers.
I-Joist hangers When manufactured wood I-joists are used they must be supported properly so that they will not collapse under normal conditions. The I-joists are set in galvanized steel joist hangers that are nailed to both the beam and the I-joists All of the nail holes in the joist hanger provided by the manufacturer must have nails in them to achieve the design strength of the system. The most common defect in I- joist assemblies is missing nails, which can significantly weaken the assembly and is often concealed by the floor deck above and a gypsum board ceiling below. Firefighters should be concerned about the types of connections used in construction with I-joists and that they are assembled correctly.
I-Joist hangers Making the I-joists More Dangerous This is a look at an altered and inappropriately installed engineered i-joist. This happens a lot when pieces don’t fit or changes are made to the original design. This is a weak spot in this floor and it will sag. It will fail much faster if it comes in contacted with fire. Be advised that this type of work is out there. After construction is completed you will never know about this potential failure point.
Further weakening of the I-Joist Knock out holes in the web will further reduce the strength of the web during fire conditions and if the I-Joist system is enclosed as in the 2 nd or 3 rd floor the fire may spread laterally.
Further weakening of the I-Joist Georgia Pacific Introduces Innovative XJ 85 Engineered Joists Strategically placed openings to accommodate plumbing, wiring and duct work. How long do you think these engineered joists will last under fire conditions??? This type of construction is why the residential home has now become our enemy. Remember, take a hook into every room, pull the ceiling from the safety of the door frame. If there is fire above you, it may be time to get out.
Further weakening of the I-Joist This is a direct quote from the fire safety information for this product: "Certain Georgia-Pacific products are specified and acceptable for use as components in fire rated building assemblies, although the products themselves are not fire rated products and are not certified or labeled as having fire resistance or endurance characteristics. Such products include, but are not limited to, 1/2" DensShield Tile Backer and Wood I beam Joists." The above quote should be a real eye opener for the firefighting community.
Fire and the I-Joist Lightweight trusses that are exposed to fire may fail in less than 10 minutes. I-Joists have been reported to fail in as little as 4 minutes and 40 seconds. Fire fighters should not enter any room or structure when it has been determined that the building’s I-Joists have been exposed to fire. Fire fighters who sound the floor with a tool to determine structural integrity will likely get a false reading from these types of flooring systems. The typical sagging of the floor may not occur.
Fire involving an I-Joist floor Seven minutes after arrival 2 firefighters fell through this floor.
I-Joist / Plan ahead for your safety Preplans and knowing how the buildings in your district are constructed has now become your best defense against buildings using I-Joist construction. Expect the unexpected. Good luck and be safe. Presentation by: TRK