The floor joists which are "Tru Joist" I beams and are 24" on center are causing sagging floors.

Question

Is there a solution to this problem? I have been advised to add 3/4" plywood diaphragm down the center spans of the three joist bays and this will solve the problem. When the home was built by "Toll Bros" 19 yrs ago they attached 3/4 inch plywood along the side of the joists to firm them up when I complained of the bounce. This stiffened the floors slightly at the time. Seems to be no cure for the 24 inch space

Answer 1

Without knowing the the size of the I-beam or the span my guess would be that the joists are carrying to much load.In which case you need more support from underneath in the form of another beam to help carry the load.You could also consider adding additional joists.

Answer 2

wood I-beam floor joists should be spaced at just over 19" (that's what those little black diamonds on your tape measure are for)
still most reputable builders stay with 16" o.c. the cost of one or
two more joists is far outweighed by the cost of a call-back.
that being said, your options are few.if the offending floor is over an unfinished space, (ie. basement or crawl space) you can add a beam and jack set-up from below. the only other solution would be to add another joist between each existing joist.

Answer 3

If you can, add a beam under it, and raise it slowly over a few days. Raising it slowly will help not to crack sheet-rock or cause cracks in hardwood floors. Also watch out for doors so they don't bind if they are near the sagging area.
If you cant leave the beam then you can double the joists, jack it all up and then glue and nail or screw the joists together.
Im curious if after your complaint, they jacked it up to put the plywood in (from BOTH sides), how tight did they rip the webbing pieces to fit, and if they glued and nailed or scewed it together.

Answer 4

The bounce you are feeling is inbetween the joists, I am guessing. The only way to get rid of the 24 space is to put in another joist. That would be a huge undertaking.
But you could try to put in cross members (joist to joist) with 2x4 on edge and box it.
Or you could resheath the floor with plywood atop of plywood where you glue and screw each sheet down. Lots of carpenters white glue and lots of screw -spaced 6" apart so 160 per 4x8 sheet. You will be making a thick sheet of plywood(instead of 5/8 you would have 1 1/4")///Another big job but doable.

Answer 5

a contruction guy here. the only thing i can think of is to run a 4x4 beam across the joist and support it with post either metal jack post putting just enough pressure on it to stop the bouncing and level the floor up some use 2-4 post towards the center of the floor not the edges you dont want to jack the house only the floor

Answer 6

ur over spanning the the joist.......u need to add a grider to break up the span ( span is the distance from one load bearing point to another) depending on the depth of ur joist, i'm guessing 14", dont span over 16 ft. .... i it is then add a double 2 x 10 yellow pine grider i the middle of the span.....remember the the new grider must have supports as in piers that should not be more than 8 ft apart and resting on a concrete footer at least 24" x24" and 12 " thick.......

lic. gen. contractor

Answer 7

if you can see the joist through the floor, then you need to add anothe flooring or reinforce underneath. if its lengthwise, you'll need jacks or(whatever they are called).or use small 1/4 inch cable and anchor it on 1 end with 2 pairs of graduated blocks and a fifth that is even taller. then the other end is a turnbuckle anchored to the beam and the cable. pull it tight to pre load the joist.

Answer 8

Its a cheap fix but you need to glue the pi$% out of the plywood. Dont know if your basement is finished, if it isnt you could put up a wall down the center (ralatively cheap). You could also double up your I joists but thats expensive and you could run into problems with plumbing an electrical. good luck

Answer 9

obviouslly cross bracing between the joist is also missing.The joists need to be tied together perpendicalarly. This will help transfer load to the adjoining joists.