{"product_id":"joist-stiffener","title":"Joist Stiffener for Bouncy and Sagging Floors \u0026 Rafters increase stiffness up to 80%","description":"\u003cp\u003eUndersized and over-spanned floor joists are common, especially in older homes. The result is a floor that bounces or flexes as you walk across it, which is uncomfortable and unsettling. The floor may be plenty strong; it just isn't stiff enough. Strength and stiffness are different things.\u003c\/p\u003e\n\u003cp\u003eThe Joist Stiffener is the result of more than two years of development and testing, and it can stiffen floor joists and roof rafters by up to 80%. Spread across a series of joists, that added stiffness can make a dramatic improvement.\u003c\/p\u003e\n\u003cp\u003eJoist Stiffeners are made from 10-gauge G90 galvanized steel. Every strap has our patent-pending interlocking key on both ends, so the straps lock together into one continuous steel flange along the bottom of the joist. Each kit includes fasteners, a pilot drill and a driver bit. All you need is an ordinary drill\/driver.\u003c\/p\u003e\n\u003ch3\u003eHow Joist Stiffeners Work\u003c\/h3\u003e\n\u003cp\u003eWhen a joist bends, its top edge squeezes together (compression) and its bottom edge stretches (tension). Stop the bottom edge from stretching and the joist can't bend as far. Steel barely stretches at all, so once the strap is screwed tight to the bottom of the joist, it works the way the bottom flange of an I-beam does.\u003c\/p\u003e\n\u003cp\u003eMost of the bending happens in the middle of the span, so that's where the steel goes. The last few feet near each support hardly move, which is why the straps don't need to run the full length of the joist.\u003c\/p\u003e\n\u003ch3\u003eTwo straps and an interlocking key\u003c\/h3\u003e\n\u003cp\u003eThe system uses two strap lengths, 46\" and 23\". Both ends of every strap have the same interlocking key (patent pending), so the straps lock together end to end and any strap can go in the middle or on the end. There are no splice plates or bolts at the joints. Each strap is fully screwed to the joist on its own, so a joint never carries the load by itself.\u003c\/p\u003e\n\u003cp\u003eKeeping every strap under four feet means a kit ships in an ordinary box and fits down a basement stairway without a fight.\u003c\/p\u003e\n\u003ch3\u003ePick your kit by joist span\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eJoist span\u003c\/th\u003e\n\u003cth\u003eStraps in the kit\u003c\/th\u003e\n\u003cth\u003eInstalled length\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e8 to 13 ft\u003c\/td\u003e\n\u003ctd\u003e23\" + 46\" + 23\"\u003c\/td\u003e\n\u003ctd\u003eabout 7 ft 4 in\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e13 to 19 ft\u003c\/td\u003e\n\u003ctd\u003e46\" + 46\" + 46\"\u003c\/td\u003e\n\u003ctd\u003eabout 11 ft 2 in\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003eMeasure the span from support to support, not the length of the board. Kits are priced per joist. Most floors need every joist in the bouncy area done. With joists 16\" apart, a 12-foot-wide room has nine or ten. For spans over 19 ft, give us a call.\u003c\/p\u003e\n\u003ch3\u003eWhich joist thickness do I need?\u003c\/h3\u003e\n\u003cp\u003eMeasure the thickness of the bottom edge of the joist.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e1-1\/2\" joist (modern lumber):\u003c\/strong\u003e Most homes built after about 1950 have standard dimensional lumber, which measures 1-1\/2\" thick.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e2\" joist (full-size, older homes):\u003c\/strong\u003e Many older homes have full-size lumber that measures about 2\" thick. Rough-sawn joists vary, often anywhere from about 1-3\/4\" to 2-1\/4\". If your joists measure in that range, choose the 2\" kit.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eNot sure? Send us a photo with a tape measure across the bottom of the joist and we'll tell you which kit fits.\u003c\/p\u003e\n\u003ch3\u003eWhat's in each kit\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eThree straps, 10-gauge (0.135\") G90 galvanized steel\u003c\/li\u003e\n\u003cli\u003e#14 x 1-1\/2\" structural screws with T25 Torx heads: 73 in the 8 to 13 ft kit, 93 in the 13 to 19 ft kit (one spare per strap)\u003c\/li\u003e\n\u003cli\u003ePilot drill\u003c\/li\u003e\n\u003cli\u003eT25 driver bit\u003c\/li\u003e\n\u003cli\u003eInstallation instructions\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eInstalling it\u003c\/h3\u003e\n\u003col\u003e\n\u003cli\u003eFind the middle of the joist span and mark it on the bottom of the joist.\u003c\/li\u003e\n\u003cli\u003eCenter a 46\" strap on the mark and screw it on.\u003c\/li\u003e\n\u003cli\u003eLock the next strap onto each end and screw it on. The 8 to 13 ft kit adds a 23\" strap on each side. The 13 to 19 ft kit adds a 46\" strap on each side.\u003c\/li\u003e\n\u003cli\u003eMove to the next joist. Do every joist in a continuous run across the bouncy area, never every other joist.\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003cp\u003e\u003cstrong\u003eRebuild the blocking.\u003c\/strong\u003e Old bridging and blocking between joists often works loose over the years. Tight-fitting solid wood blocking the same height as the joists, screwed through the joists into the ends of the blocks, spreads the load across the stiffened joists so they work together.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdhesive is optional.\u003c\/strong\u003e In our testing, construction adhesive under the strap didn't add stiffness over screws alone. If you'd like to use it anyway, we recommend Loctite PL Premium MAX.\u003c\/p\u003e\n\u003cp\u003eEach joist takes 70 to 90 screws, so a whole floor adds up fast. An impact driver is the right tool for the job.\u003c\/p\u003e\n\u003ch3\u003eGood to know before you order\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eTested.\u003c\/strong\u003e In our lab, Joist Stiffeners made floor joists up to 80% stiffer.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt's for sound joists that bounce or sag.\u003c\/strong\u003e If a joist is cracked, broken, notched or has a large hole cut in it, repair that first with one of our \u003ca href=\"\/collections\/featured-products\"\u003ejoist reinforcers\u003c\/a\u003e.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt won't lift an existing sag.\u003c\/strong\u003e It stiffens the joist from where it is now and helps keep the sag from getting worse. We don't recommend jacking old joists before installing.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt stiffens joists, not everything else.\u003c\/strong\u003e It won't fix a springy subfloor between joists, a sagging beam or a failed post.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThinking about tile?\u003c\/strong\u003e Ceramic tile and grout crack when the floor under them flexes too much, and natural stone is even less forgiving. Stiffening the joists before the tile goes down is a lot cheaper than redoing a bathroom floor.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIt adds about 1\/4\" below the joist\u003c\/strong\u003e (strap plus screw head). Drywall can still go up underneath; furring strips beside the strap give it a flat surface.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eJoist Stiffener straps are made in our Roanoke, Virginia factory.\u003c\/p\u003e","brand":"Skyline","offers":[{"title":"8–13 ft Kit (includes fasteners) \/ 1-1\/2\" joist (modern lumber)","offer_id":67355130593521,"sku":"JS-08-13","price":59.95,"currency_code":"USD","in_stock":true},{"title":"13–19 ft Kit (includes fasteners) \/ 1-1\/2\" joist (modern lumber)","offer_id":67355130626289,"sku":"JS-13-19","price":84.95,"currency_code":"USD","in_stock":true},{"title":"8–13 ft Kit (includes fasteners) \/ 2\" joist (full-size, older homes)","offer_id":67511731192049,"sku":"JS-08-13-2","price":59.95,"currency_code":"USD","in_stock":true},{"title":"13–19 ft Kit (includes fasteners) \/ 2\" joist (full-size, older homes)","offer_id":67511731224817,"sku":"JS-13-19-2","price":84.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0275\/0169\/1018\/files\/Stiffening_Strap-24-MAIN.png?v=1793208046","url":"https:\/\/joistrepair.com\/products\/joist-stiffener","provider":"JoistRepair.com","version":"1.0","type":"link"}