Home built in 1989 with bouncy floors
user-5200119
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Standard builder ome built in 1989 with I Joists but on 24 inch centers. Floors are bouncy and we would now like to tile the kitchen and family room as no wood product holds up to our labrtadoodle. Any advice or techniques to brace up this floor. Subfloor is plywood not particle board.
Replies
how much space do you have under the house?
how far are joists that are causing trouble spanning?
Bouncy floors
Full basement with drop ceiling that I can get out pretty easy. Some duct work interference, minor pwater lines and some minor electrical that I have to take down
if you have enought space in the drop ceiling to add a beam (perpendicualr to joist direction) and have it be in between drop ceiling and joist, this would be the easiest and probablly most efficient way to eliminate your bounce. This would only leave you with the columns to deal with in the basement area.
running smaller joist will be very intrusive and probablly considerablly much more challenging to manuver 17'-18' joist in place through all the existing machanicals, electrical and plumbing.
with a beam, you could use steel with a much smaller depth than lumber (if your space is limited).
bouncy floors
also I joists are plywood web sandwiched between two laminated veneer lumber top and bottom not a 2x4 on top and bottom.
bouncy looks
Span is around 16 or 17 feet I was thinking of adding a nother i joist between the original but slightly smaller then using blocking to wedge. So it would be a joist every 12 inches which may stop the bounce but I believe ill have to consult span charts to see if a smaller one will work.
glue and screw (nail ok if yoou let glue cure befor loadihg the floor) a 20 ft 2x4 to the bottom chords.
Make sure the plywood has nails every 3" for the outer 4 ft of the span before you tile.
bound floors
The plywood subfloor was previously screwed down years ago to eliminate squeeks when we recarpeted
Reconsider Tile
Why? Because you're living in a house that was carefully built to the absolute minimun standards. Strengthing the floor nearly requires starting over!
There are two things to look at first.
First of all, you almost certainly have only 3/4" subfloor; tile requires a minimum of 1-1/8" for stiffness. Be sure to use tingue & groove subfloor material - not just any plywood.
Next, the easiest way to stiffen the joists is to make their span shorter. You do this by installing a beam across the halfway point and supporting it on lally posts. Additional blocking between joists will also help.
What other flooring is there? Well, I'd look at rubber tiles; anything that stands up to horse hooves will survive a dog. If you want, cover the rubber with sheet vinyl, prinyed to look like wood.
If you can break your existing joists at mid-span with a drop beam in the basement, that'd probably be your easist and most effective solution. I'd say your idea of adding additional joists would be second. Adding shorter, but stiffer (doesn't have to be same type of manufacturer) joists and blocking is a smart way to simplify your retrofit.
Remember that your tile underlayment prep will also be important for a succesfull tile install. . Most TCNA (Tile Council of North America) details for 24" O.C. engineered joists involved plywood underlayments of 3/8" or more and are fastened with a particular placement and schedule. You might want to review one that meets guidelines based on your particular tile installation plan.
Do make sure that the bounce you're feeling is in the framing and not the subfloor. You need more subfloor anyway, so that would fix subfloor bounce.
And check that proper cross bracing is installed. Cross bracing is quite effective in reducing bounce.
Comments and solution..
Just a quick comment .... long spans for floors often create deflection issues. The Code deflection criteria for floors is L / 360 (length in inches divided by 360) is fine for short spans, but be problem for long ones. At your span of 16' (192") the allowable deflection would be 192" / 360 = .533". If the span were 8' (96"), the allowable deflection would be 96" / 360 = .266". In the same space, the allowable deflection would be twice as much for a 16' span as two 8' spans. The room with the longer span will have a much "bouncier" floor.
As mentioned above, make sure there's blocking or bracing between the joists. Often these joists are designed assuming there's a material like drywall attached to the underside of the joists...this surface also acts similar to cross bracing and helps brace the bottom chords of the trusses. Because I joist are so weak laterally (to see this, just pick one up when it's laying flat..), it's critical they are properly braced. Otherwise, the bottom chord is allowed to move sideways when a load is introduced.
Obviously, putting an additional beam under the joists is a solution...wouldn't have to be down the center...anything to lower the span will help. But that likely will require additional columns and footings.
Another solution - sheath the sides of the joists with plywood or OSB. Glue and nail sheathing to each side of the top and bottom chord (you'll need to provide short solid blocking pieces 8' apart at plywood joints along the length of the joist). We've done this several times with I joist and open web trusses when we've made openings if floor or roof framing and needed adjacent trusses to carry more load. This should stiffen the joists significantly without the need of addtional joists...or much cost.