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Open Joist™Floor System Performance: a Matter of Perception

Open Joist™ floor trusses are engineered for superior strength, which can be used to achieve optimum floor system performance or to maximize floor framing efficiencies.

It should be recognized that floor system performance is a very subjective issue for those who occupy a structure. One person's opinion of how a floor should "feel" can differ markedly from that of another person. And, meeting minimum building code requirements does not always result in end-user satisfaction.

The two most common performance factors that influence an individual's opinion of a floor system are deflection (bending) and vibration. United States model building codes restrict the amount of deflection under load permitted in floor systems but only the Canadian codes prescribe vibration standards.

When designing a floor system, consideration should be given to the following practices and conditions that have direct effects on floor deflection and floor system vibration reduction:

Ways to Reduce Deflection:
  • Deeper floor trusses.
  • Reducing the on-center spacing of floor trusses.
  • Thicker floor decking.
  • Installing floor decking on floor trusses with both adhesives and fasteners.
  • Using a bearing wall to support the ends of floor trusses (rather than a suspended beam) results in a stiffer floor system.

Ways to Reduce Vibration:

  • The presence of framed partition walls and other permanent dead load components.
  • Applying drywall to the underside of floor trusses (i.e. basement ceiling).
  • Proper installation of "strongback" bracing within the floor truss system will restrict deflection and help dampen floor system vibrations.

Poured toppings (lightweight concrete, etc.) can have a positive or negative effect on the performance of a floor system depending on circumstances.

In an effort to satisfy floor system end-users who carry heightened perceptions and expectations, consideration should be given to the preceding factors when designing floor systems.

Acoustical Performance/Characteristics

To download one of the details below, right-click or Ctrl-click on the link, then choose “Save Target As” or “Save”.

  Acoustical Performance Assembly - DWG / PDF
Acoustical Characteristics Table – PDF