Pros: Doesn’t interfere with plumbing or wiring in joist bays.Ĭons: Reduces headroom bottom edges of joists must beīlocking, short pieces of 2x stock the same depth as the joists, stops sideways deflection and ties the joists together so they can effectively share floor loads. Use a temporary 2×4 post at the midpoint of the span to support the joist until the adhesive cures (usually in 24 to 48 hours). Tom bonds the two together with construction adhesive and sinks a 12d nail up through the 2×4 every 8 to 12 inches.
Springy block end feel full#
For this method to work, the 2×4 must be long enough to run the full length of the joist. Adding a 2×4 to the underside helps keep it from doing this. When a joist deflects, its bottom edge stretches slightly.
Springy block end feel free#
Pros: The best choice for preserving headroom.Ĭons: The joist bays must be free of any obstructions, such as electrical cables, ductwork, and plumbing, while you’re doing the work. Tom always runs a bead of adhesive along the top edge before putting the new joist in place. 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.) Fasten new lumber to old using pairs of 12d nails every 16 inches. For joists made of sawn lumber, shown here, Tom attaches a 2x of the same length and width if the bounce is severe enough, he may use an engineered or laminated veneer lumber (LVL) beam. Photo by Richard Howard 4 Ways to Stop the Bounceĭoubling the thickness of joists by adding material to their sides increases strength and stiffness. Remembering his boyhood kitchen, Tom makes sure that any new floor he builds is rock-solid. Stiffening upper floors typically requires removing some or all of the finished ceiling below. Tom’s solutions, shown here in order of effectiveness, are easiest on the first floor, where joists are accessible from the basement or crawl space. For example, sistering with new lumber-the fix Tom’s dad used-makes sense only if the joist bays are not cluttered with electrical cable, plumbing lines, and ducts. There are a variety of ways to stiffen a floor the method (or methods) Tom chooses depend as much on practicality as on effectiveness. Even structurally sound, code-compliant new floors can deflect, or flex, more than feels comfortable. Tom’s house was built in 1765, but bouncy floors aren’t just an old-house problem. Eventually his father, a carpenter, went down to the basement with Tom in tow and reinforced the undersized floor joists.
Whenever anyone walked across the kitchen floor in the home where This Old House general contractor Tom Silva grew up, teacups trembled in their saucers and pots and pans rattled on the stove.
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