Renovation-Headquarters Banner

Flooring - Deflection and Vibration

Deformation of Floor Joists - 2

Problem: Deformation of flooring joists - 2


Excessive overlapping of joists at beams.

When joists are subjected to loads, they deflect in the middle. This middle deflection results in the joists pivoting at the supports. If the joists are extended over the supports, the pivoting at the end will result in lifting occurring beyond the support as shown in Figure 23.

Excessive Joist Overlap At Supports
Figure 23 - Excessive Joist Overlap At Supports


Reduce the amount of joist projection beyond the beam:

  • Since joists will always deflect under load, the effects of the deflection must be minimized. Do not extend joists more than 2″ (50 mm) beyond the beam. In fact, many builders cut the joists so that they do not overlap. Butting them end to end over the support instead. Bottoms of floor joists must be restrained from twisting by toe-nailing to
Proper Overlap For Joists
Figure 24 - Proper Overlap For Joists