Engineered Floor Joist Bounce

For joists made of sawn lumber shown here tom attaches a 2x of the same length and width.

Engineered floor joist bounce.

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. People are particularly sensitive to frequencies in the 8 to 10 hz range. Much bounce though can make the china cabinet wobble. Still stronger is a flitch beam which uses a steel plate bolted between the old joist and its new sister.

The best choice depends on access to the joists obstructions in the floor system or current remodeling plans. These joists perform very well on paper. 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. 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.

With joists 16 inches on center this floor sheathing has a code plus allowable live load of 240 pounds per square foot. A copy of the joist calc is attached. And a structural engineer thor matteson author of wood framed shear wall construction guide international code council 2004 gives expert advice about how to correct a bouncy i joist floor. 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.

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. For joists made of sawn lumber shown here tom attaches a 2x of the same length and width. The spans for joists according to the code is far more than we find acceptable. As a footstep falls on one joist some of the force is transferred to neighboring joists.

At higher frequencies vibrations are perceived as less annoying. I can often feel it when somebody walks through the room. 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. If the bounce is severe enough he may use an engineered or laminated veneer lumber lvl beam.

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. Live load l 869 26 total load l 644 35. Bridging or x bracing allows joists to share weight. There are six choices.