I am having trouble reducing the bounce in my living room celling (above is the bedroom) The room is 18 feet wide by 30 feet long….2 by 10s run 16inches oc, I have glued and screwed 2 layers of 9inch osb board to the 2 by 10 …didn’t work so today I added some Tgi inbetween the 2 by 10s screwed the sub down and we still have bounce. We plan to put in hardwood flooring but can’t see that completely stopping the bounce.
At this stage a steel beam is not an option because of post positioning problems. Have also thought about another sheet of ply for the bedroom subfloor?
Any suggestions what else I can do.
Thanks
Dave
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Consider plywood glued and screwed to the bottom of the joists.
Thanks for the replys. The only concern I have with adding more weight to the joice is sag, I have thought about running 2by4s glued and screwd but again lots of extra weight. extra ply or osb will also I think create sag
I think I will order more TGI to add to the recent instaled ones hopefully this will add more strenght and help reducing the bounce.
I have screwd the subfloor really well and this has stiffend up the bedroom floor however my concern is the drywall cracking on the ceilling below. I can also build a frame independantly from the ceilling to support the drywall however this will need to be 2by6 because of the span, this will probally lower the ceilling to much as I have ducts running on the side walls.
I think after the new TGI are installed I will just have to live with the bounce and hope over time the sag or bounce doesn't effect the drywall, bit annoying really when I was told that the TGI are over kill and will definatly work, it's helped but not worked.
Again thx guys keep the ideas coming.
Do you mean "TJI"?
Do you mean "TJI"?
"I think I will order more
"I think I will order more TGI to add to the recent instaled ones hopefully this will add more strenght and help reducing the bounce."
Like I said before - Adding more to the sides will do little or nothing. You need to add depth to reduce vibration.
Here's an old post I did about floor vibration:
http://forums.finehomebuilding.com/breaktime/general-discussion/floor-vibration
It explanis my reasoning for what I said above.
An 18 foot span is going to bounce no matter what you do, but the suggestion to apply osb or ply to the bottom of the joists is a good one. Ideally glue and screw directly to the joists.
The only thing that will reduce bounce is more depth in the floor system. Addind stuff to the side of something that's way too shallow is pointless.
Is there strapping on the bottom and bridging between? That will help to increase the allowable span for a 2x10, but not near as far as you need it to go. Otherwise, it might be a good idea to consult a structural engineer to see if doubling up some of the joists would help, or if he has any other suggestions.
If you were my client 3/4 ply on the bottom of the joists is what I'd do and there will definitely be a difference in the floor. All ply edges should have blocking spaning the two sheets - two layers of 6" wide ply turned on it's side is ideal.
If you don't believe me take two 18' 2x10's 16" apart with whatever ply you have as subfloor. Put a 4x4 under each end and stack 1000 lbs of crap in the middle and measure the deflection. Add the 3/4" ply to the bottom and repeat it. You'll be shocked how stiff it is. I use this method when saving headroom in weird situations, on unsupported pony walls, long industrial shelves and a number of other situations.
Don't put 7/16" osb, or any osb, on rather than the thicker ply - I wouldn't use anything less than 3/4" ply with fasteners every 4 inches along each joist.
The reason it works so well has to do with how wood joists behaive while being bent - the top doesn't compress as easily as the bottom stretches. Adding extra subfloor to the top doesn't help nearly as much because the top isn't compressing all that much to begin with.
Why ply and not a 2x on the bottom of each joist - because the ply stiffens in both directions so as someone walks across a floor their weight is spread out more.
Along similar lines, if it were me after the ply is up I'd use a hole saw matching the diameter of the blower hose used with a cellulose insulation blower and make a hole on each end of a joist space and blow it full of insulation. It will deaden sound and actually make the floor feel different when you walk on it - my building partner did this with his house and it was shocking how well the sound deading of the cellulose is! Fiberglass doesn't come close to the sound deadening of cellulose.
Having said all that there are many options with steel other than just a big beam to shorten the joist spans. Unfortunately steel prices are such that adding sizeable steel joists is costly (I'm talking thick walled structural stuff, not light gauge stamped steel floor joists). When a unique situation comes up I like to stop by the used steel yard and see what's there for pennies on the dollar. I've seen times when there is enough structural C channel and/or small I beams to frame an entire floor such as yours.
Also if you're running a large beam it doesn't have to simply go from one end to the other. If it works better for the load path beams can be run in a "T" shape with most of the spans being cut in half and some of them changing direction, but over a shorter span. An "H" shape is likewise just as doable. The engineering is nothing special and the intersections are a simple bolt together T-shaped plate made from scrap I beam. In fact that simple connection plate can be used when connecting to concrete or even in place of a joist hanger if you're using small size I beams in place of joists.
Blocking the plywood edges is essential and the face grain should run parallel to the joists, since it is in tension. The whole floor assembly works like a box beam.
Thx so much guys really helpfull info.
I arrived today onto the jobsite and discoverd that 10 new TJI have been installed and this has really helped with the bounce, luckily enough room for ductwork and pot lights.
The ply wood sounded like the better option unfortunatly this option was not agreed upon.... so I can't dwell on things so my next question will be, I need to apply strapping for the drywall what if I put 2by4s as the strapping and glue and screw this to the TJI will this act a little like the ply wood approach, if so how should I space them 16 oc
Again huge thx guys for all the help
Dave
The strapping may help a little by acting like blocking but it will act nothing like the plywood since it does nothing to add a tension member to the bottom of the joists. I'd use metal hat channel or acoustic channel instead of the 2x4s. If you don't know what those are ask at your local drywall supply, not HD.
I made some like the Luxor bridging, and they do really work.
If you do make some, glue the center joint.
Must say they would be easier to put in before the plywood was installed on floor.
http://www.luxorcorp.com/IBS.html