Engineered Floor Joist Bounce

Bridging or x bracing allows joists to share weight.

Engineered floor joist bounce.

For joists made of sawn lumber shown here tom attaches a 2x of the same length and width. Floor joists whether they be solid wood engineered lumber like yours or even steel can deflect or bend under a given amount of weight and a given amount of span. And using a liberal amount of floor construction adhesive i like to see squeeze out on both sides of the joist can stiffen the floor sheathing even further by limiting rotation at the connection. Yet something as simple as my dog pacing through the great room can create some bounce in the floor.

With joists 16 inches on center this floor sheathing has a code plus allowable live load of 240 pounds per square foot. We have engineered this calculator to provide spans which will produce a solid built house with no bounce in the floors or any swags in the ceiling. The spans for joists according to the code is far more than we find acceptable. The best choice depends on access to the joists obstructions in the floor system or current remodeling plans.

If the bounce is severe enough he may use an engineered or laminated veneer lumber lvl beam. If the bounce is severe enough he may use an engineered or laminated veneer lumber lvl beam. These joists perform very well on paper. There are six choices.

Much bounce though can make the china cabinet wobble. The floor bounce or vibration felt when walking on the floor is related to the frequency of the vibration which is a function of the floor joist size and span. A copy of the joist calc is attached. Even if your joists already have a row of bridging at the center of the span adding a row on each side of the existing bridging will stiffen the floor.

You can shore up floor joists and reduce the bounce in a number of ways but the six methods outlined here represent a mix of common and not so common solutions. Still stronger is a flitch beam which uses a steel plate bolted between the old joist and its new sister for sistering i joists see page 4 of this article. At higher frequencies vibrations are perceived as less annoying. For joists made of sawn lumber shown here tom attaches a 2x of the same length and width.

As a footstep falls on one joist some of the force is transferred to neighboring joists. I can often feel it when somebody walks through the room. People are particularly sensitive to frequencies in the 8 to 10 hz range. If you take a 2x10 solid lumber floor joist that is spanning 16 feet and place a 94 pound sack of cement in mid span the floor joist will bend downwards a given distance.