What Is Floor Joist Bridging

Bridging of roof decks is also needed for wind uplift conditions where stress reversal can occur putting bottom of joists into compression lateral stability concern.

What is floor joist bridging.

While it does not offer as much support or prevent joist flexing as well as solid blocking does cross bracing does have some definite benefits. Section r502 10 of the international residential code states that header joists can be the same size as the floor joists when the header joist span isn t greater than 4 feet but if the header joist span is more than 4 feet you ll need to double the header joist and ensure that it s capable of. I joists are joists built with structural integrity however they still benefit from bridging which also helps reduce vibrations in the flooring. Bridging ties the joists together with lumber.

The joists immediately under the load deflect substantially before the straps are tensioned and start spreading weight to other joists. Floor joist bridging is critical to the structural strength of a floor as shown in figure 1. If bridging is intended to brace other components of the structure the size and connections must be indicated on the contract documents. The most common justification of bridging in floor systems is to load share between joists especially under point loading such as foot traffic.

Even if your floor already has a row of bridging running down the center you can stiffen it substantially by adding two more rows. Bridging allows each joist to share weight with its neighbors and can cut deflection how much the joists flex by half. Joist bridging is used in construction with long span lumber as a load sharing device. Normally these systems are independent of the joist system.

In general those values are in the sji bridging tables in the specification. Additional support for the floor joists is achieved by nailing the ends of the joists into headers. Proper bridging distributes the load on the floor to other joists and over time prevents floors from sagging and squeaking do to floor joists twisting and warping. The catch of course is that the bouncy floor joists must be accessible from below.

Blocking when talking about floor joists is when short wood blocks are used to fill or reinforce floor joists under floors that have a space below them. Properly installed wood x bridging tightens as the joists shrink to the degree that i ve seen the bottom of the joists get a slight crook in them from the bridging. Yet it is not uncommon to find bridging not properly installed or missing all together. It distributes the weight of a person walking onto multiple joists.