Article and photos by Gregory Havel
When a structure is built using I-joists, there are no natural openings provided for running pipes, cables, and ducts, as there are in open-web trusses. Electricians, plumbers, and air-conditioning installers have to make their own openings, as will the do-it-yourself owner.
Most I-joists are designed and installed according to the ASTM D5055, Standard Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I-Joists, which includes Section 6.6.3 on web openings, and the recommendations of the Wood I-Joist Manufacturers’ Association (WIJMA) www.i-joist.org. Model building codes, as well as state and local codes, may also apply NFPA 5000, Building Construction and Safety Code, 2009 edition. Chapter 45.5.5 incorporates by reference ASTM D5055, as does the International Residential Code, 2009 edition, (International Code Council) in Chapter R502.1.4.
According to the WIJMA document Establishing Shear Capacities for Prefabricated I-Joists with Holes, the amount of web material that may be removed safely varies with the dimensions and materials of the top and bottom members of the I-joist; the material, thickness, and height of the web; the type and strength of connections between the members and the web; and the size and shape of the hole (Photo 1).
The WIJMA document does the following:
The complete document is a free download at http://i-joist.org/shear%20with%20holes.pdf.
Holes in I-joist webs must be cut or drilled. In Photo 2, the holes were pounded through the webs with a hammer, which can weaken the webs. These holes are of irregular sizes and shapes that have not been tested by ASTM D5055. This method also makes it difficult to keep the hole in the middle third of the web as required. At this construction site, the building inspector required the contractor to repair these web holes as the joist manufacturer recommended in writing and to drill new holes at a new location.
Manufacturer’s instructions are usually included with each shipment or bundle of I-joists; they include information on permitted web hole sizes, shapes, locations, and spacing; prohibited locations for holes; and the procedure for obtaining approval of any modifications not covered in the instruction booklet. Some manufacturers mark acceptable locations for web holes on each I-joist. Others provide “knock-outs” or three-sided pre-cuts for holes in the web in acceptable locations, shapes, and sizes.
A good working relationship with the local building inspector will instill in firefighters some confidence that the I-joists were installed with permits and inspections and were done correctly; and will allow firefighters to contact the building inspector if they have visited a construction site and observed something that isn’t right. No matter how conscientious your building inspector is, it is possible to miss details. These kinds of details are visible only during certain stages of construction, will be concealed for the rest of the building’s life, and could lead to an early structural collapse at a fire incident, or even if no fire is present.
Gregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC
Subjects: Building construction for firefighters, I-Joists