- Truss placement diagrams (TPD) are intended to assist in positioning trusses and related components supplied by the component manufacturer.
- On residential projects, the truss design engineer is responsible for the single truss design depicted on each truss design drawing.
- Since the TPD is not typically prepared under the truss designer engineer’s supervision, it is not considered an engineered document.
- It is not legal in most states for a truss design engineer to seal a non-registered person’s work for which he has
- The building designer should specify permanent building stability bracing on the construction documents.
- If the building designer does not provide this bracing on the construction documents, the IRC 2006 specifies that BCSI must be followed.
- Wind and seismic loads applied to the gable frame laterally need to be resisted as shown in Figure 4.
- Continuous studs are required to eliminate hinge points in gable end walls per the 2009 IRC.
- The “all walls” language has been clarified by allowing mixing of braced wall methods.
- The wall bracing section of the 2009 IRC has been extensively rewritten and reorganized.
- Lumber design values, not loads, are adjusted by the load duration factor (LDF).
- The application of LDFs is separate from load combining reduction factors, although both may be used in truss design calculations.
- In areas where snow load controls the design, code allows an LDF of 1.15, not 1.00.
- Partition separation is often blamed on a condition known as truss arching.
- Wood may expand or shrink depending on its moisture content.
- The example given in Figure 2 shows that a 28-ft truss with 19% moisture content that dries to 7% may cause an upward deflection of about 0.7 inches.
- Many factors lead to partition separation; the only way to prove truss arching is to use a laser level to assess all the areas of potential movement in the structure.
- Any lumber that is graded to assign design properties is considered stress-graded, no matter if it was visually or mechanically graded.
- Material with design properties listed in the NDS Supplement or in individual lumber use guides is considered stress-graded.
- The IBC does not prohibit the use of exposed truss bottom chords.
- Since interior grade OSB is allowed on the underside of an exposed truss, it follows that there would not be a more stringent requirement for exposed trusses.
- The USDA Forest Products Laboratory’s Wood Handbook provides the average equilibrium moisture content of wood exposed to the outdoor atmosphere for various cities in the United States.
- Conditions like deflection and vibration can occur in metal plate connected wood trusses even if they meet the building code and adequately transfer loads.
- When stone flooring is installed over wood frame construction, deflections not exceeding L/720 are recommended.
- The Building Designer is responsible for providing the deflection criteria and on-center spacing requirements to limit deflections.
- If no building design information is given, truss technicians should not assume deflection criteria of L/360.
- Two common conditions that impact drywall are known as cracking and ridging.
- These conditions can be caused by temperature and humidity changes or insufficient framing techniques.
- The Gypsum Association and the Drywall Finishing Council have provided guidelines for trades working with gypsum board.
- To add insulation into a tested assembly, an equivalent or greater plenum space should be maintained and the insulation held up and away from the gypsum surface.
- Increasing the depth of an assembly does not adversely affect its fire endurance rating.
