1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)

Bouncy floor

Post in 'DIY and General non-hearth advice' started by chrisasst, Feb 12, 2013.

  1. chrisasst

    chrisasst Minister of Fire

    Joined:
    Aug 13, 2008
    Messages:
    1,203
    Loc:
    cortland ny
    I have 2 rooms that I am gutting...etc.. The one room is right above the other. And the bottom room is right above my basement. The upper floor is very bouncy. What can I do to support this. I am thinking I need a beam of sorts right? Kind of like a load bearing beam or something right...

    Or any other suggestions?

    Helpful Sponsor Ads!





  2. lukem

    lukem Minister of Fire

    Joined:
    Jan 12, 2010
    Messages:
    3,687
    Loc:
    Indiana
    Add joists.
  3. Morgan

    Morgan Member

    Joined:
    Apr 24, 2010
    Messages:
    111
    Loc:
    PEI, Canada
    Pictures would help getting some ideas coming your way. Sight unseen here is what I can offer, you could double up the floor joists (if they are not full of wires and pipes and what not. You could add in some sort of beam but the load of this beam would have to carry straight through to your basement. Sometimes just adding blocking between the joists can take some spring out of a floor. Post some pics, let us see =)
  4. Jack Straw

    Jack Straw Minister of Fire

    Joined:
    Dec 22, 2008
    Messages:
    2,161
    Loc:
    Schoharie County, N Y
    Diet?;lol
    Eatonpcat, swagler85 and milleo like this.
  5. chrisasst

    chrisasst Minister of Fire

    Joined:
    Aug 13, 2008
    Messages:
    1,203
    Loc:
    cortland ny
    I will get some pics tomorrow. I tried blocking between the joists and didn't help.
  6. Ehouse

    Ehouse Minister of Fire

    Joined:
    Jul 22, 2011
    Messages:
    903
    Loc:
    Upstate NY
    Two tricks I can think of;

    Glue and nail a bottom flange to each floor joist turning them into I-beams.

    Stretch a taught 1/4" cable across the bottom of the joists in the middle and perpendicular.

    Ehouse
  7. brian89gp

    brian89gp Feeling the Heat

    Joined:
    Mar 15, 2008
    Messages:
    468
    Loc:
    Kansas City
    What size joist and how long of a span?

    -Doubling a joist up (going from one 2x8 to two 2x8's sistered together) is roughly the same stiffness going 2" more in depth (going from 2x8 to 2x10)
    -A LVL or PSL of the same dimensions is stiffer then sawn lumber.
    -Full height solid blocking at 1/3 spans will stiffen up the floor slightly as it transfers the point load of your feet to other joists

    If you do a beam you are probably going to have a pretty decent sized beam and you need to support the point loads all the way down to the basement
  8. Frozen Canuck

    Frozen Canuck Minister of Fire

    Joined:
    Dec 14, 2009
    Messages:
    858
    Loc:
    North central Alberta, Canada
    Bridging will perform better than blocking & when you do the gut if you dont see any bridging thats a large part of the reason why you feel a bounce. Unless of course the joist are undersized for the span.
  9. Ehouse

    Ehouse Minister of Fire

    Joined:
    Jul 22, 2011
    Messages:
    903
    Loc:
    Upstate NY
    One more;

    Glue-nail 1" or 3/4" plywood on the face of the middle third of each joist (partial sister). If the bellies are stiffened the ends will not deflect much if at all. It's important to have close nail spacing.

    If you take this ,or a similar approach, start with the middle joist or two, then test the floor. It's deflecting in all directions not just along the lengths of the joists (as a diaphragm). 3 or 4 joists in the middle might be enough.
  10. jharkin

    jharkin Minister of Fire

    Joined:
    Oct 21, 2009
    Messages:
    3,329
    Loc:
    Holliston, MA USA
    Wont make a significant difference. Its the vertical face of the I-beam that imparts stiffness up and down.
    Eatonpcat and woodgeek like this.
  11. jharkin

    jharkin Minister of Fire

    Joined:
    Oct 21, 2009
    Messages:
    3,329
    Loc:
    Holliston, MA USA
    Chrisasst,

    I think that to really give sound advice we need to first understand why the floors are bouncy. There could be many reasons - some quite simple and easy to rectify, others not so much.

    It could be any one of:

    • The finish and/or subfloor may just have pulled away from the joists (not uncommon if its a 100+ year old place with face nailed wood flooring)
      • This can be rectified by re-nailing, or better screwing down the floors. Tom Silva on TOH once showed a neat screwing system where the screw heads broke to be invisible
    • The joists may have been weakened by years of plumbers and electricians notching them out to run pipes, ducts and wires
      • Obvious fix here is to sister the offending joists
    • the joists may have been undersized to begin with.
      • A builders span table will tell you if this is the case, and if so, fix is to add more joists or a support beam and/or posts (if going the beam/post route you might want to consult a structure engineer)
    • A load bearing wall might have been removed at some point
      • Here again we are looking at adding support beams, etc.... engineer time

    Pictures, any detail on the above ideas, and some more info on the age and construction of the house will help. (all of the above assumes the place is less than 100 years old and a typical platform frame house. If its stone, or is older and of either balloon or post/beam framing there are even more possibilities to consider)
  12. ironpony

    ironpony Minister of Fire

    Joined:
    Jan 22, 2010
    Messages:
    1,844
    Loc:
    mid-ohio via St.Croix USVI

    exactly, 1/2 plywood or OSB will add more rigidity then a sister joist,. there are so many variables this is hard to remedy without pictures and more info
    age of house would help greatly
  13. jharkin

    jharkin Minister of Fire

    Joined:
    Oct 21, 2009
    Messages:
    3,329
    Loc:
    Holliston, MA USA
    Agreed. I just thought of another possibility, could even be failed joist hangers. I'm sure there are others I'm not thinking of also.
  14. ironpony

    ironpony Minister of Fire

    Joined:
    Jan 22, 2010
    Messages:
    1,844
    Loc:
    mid-ohio via St.Croix USVI

    or like the house I was in yesterday with the joists hangars installed with 8D nails in less than half the required pattern
  15. Beer Belly

    Beer Belly Minister of Fire

    Joined:
    Oct 26, 2011
    Messages:
    1,717
    Loc:
    Connecticut
    I have the same problem with bouncy floors, and I'm gonna glue and screw 1/2 Plywood on every Joist.....one of these days:oops:
  16. Ehouse

    Ehouse Minister of Fire

    Joined:
    Jul 22, 2011
    Messages:
    903
    Loc:
    Upstate NY
    Don't wish to argue with you gents, but a TJI with a mere 1/2" ply or OSB web will span considerably more than a 2x joist of the same depth, and be stiffer to boot.
  17. chrisasst

    chrisasst Minister of Fire

    Joined:
    Aug 13, 2008
    Messages:
    1,203
    Loc:
    cortland ny
    20130213_113054.jpg 20130213_110112.jpg 20130213_110156.jpg 20130213_110303.jpg

    The house is a 1900 house. When I moved in there was carpet in the upper room. Which I ripped out. All that was/is under that is T&G boards. All of them appear to be still attached to the joist.

    The first pic is when you walk into the room.
    Second pic is the area ( middle) where it is bouncy
    Third pic is showing they fastened the joist ( if you can see it)
    Fourth pic is a corner / window I have no idea what to do with.

    As you can see someone put up newer joists next to the old ones.
  18. ironpony

    ironpony Minister of Fire

    Joined:
    Jan 22, 2010
    Messages:
    1,844
    Loc:
    mid-ohio via St.Croix USVI
    please reread what I wrote, that is exactly what I said, plywood and OSB will add MORE rigidity than a sister joist
  19. jharkin

    jharkin Minister of Fire

    Joined:
    Oct 21, 2009
    Messages:
    3,329
    Loc:
    Holliston, MA USA
    OK, yeah we can see its been sistered already, but no obvious big notches in the joists. So, Im guessing the problem is the joists are undersized for the span spacing or some supporting wall was removed.

    The one thing I can quite tell from that third image is how the joists are attached. In balloon framing the studs run from the mudsill all the way to the top plate in the attic, and the second floor joists would be nailed to the sides of the studs, and should also be supported on a ledger band that is notched into the studs. Platform framing is modern construction where the second floor joists sit on top of the plate for the first floor.

    Either way I have to punt at this point at being beyond my depth to advise on the best course of action.
  20. ironpony

    ironpony Minister of Fire

    Joined:
    Jan 22, 2010
    Messages:
    1,844
    Loc:
    mid-ohio via St.Croix USVI

    agree with above, there are many issues here that need to be looked at first hand, span, joist size, spacing, connection etc.
  21. semipro

    semipro Minister of Fire

    Joined:
    Jan 12, 2009
    Messages:
    2,412
    Loc:
    SW Virginia
    It may have been covered already or you may have dismissed early on as an option;
    adding a post with a beam perpendicular to the existing joists seems the simplest solution to me. The post would need to be supported all the way to the basement floor somehow (not just to the first floor).
  22. brian89gp

    brian89gp Feeling the Heat

    Joined:
    Mar 15, 2008
    Messages:
    468
    Loc:
    Kansas City
    2x8 joists with 24" spacing on what looks like a 12-14' span? That would definately flex a bit.

    Couple things I see:
    1. Only partial height blocking, not that full height blocking helps all that much but partial height blocking doesn't really do anything at all.
    2. Looks like someone used two new pieces of lumber to sister each joist as I see joints in the middle. It should be one piece end to end otherwise it doesn't do much (or use a very liberal amount of glue and fasteners, probably cheaper to just buy a longer joist)

    Either properly sister the joists, go one or two sizes up in the joists, or put a beam in. FYI, a beam to hold a floor mid-span over a 12-14' unsupported length is pretty large.
  23. Ehouse

    Ehouse Minister of Fire

    Joined:
    Jul 22, 2011
    Messages:
    903
    Loc:
    Upstate NY

    Thanx for the heads up to reread your post, the first word of which was "exactly" with a reference above to jharkin's which stated "Its the vertical face of the I beam that imparts stiffness up and down."

    Please reread what I wrote; I was not talking about sistering at that point. At any rate , it's about a bouncy floor, and now that I've seen the pics., I think first responder lukem had it right. Add joists to make 12" spacing
    lukem likes this.
  24. lukem

    lukem Minister of Fire

    Joined:
    Jan 12, 2010
    Messages:
    3,687
    Loc:
    Indiana
    At that span I'd add the joists to make it 12 OC. Sistering won't help a ton as you seen because a lot of the bounce may be coming from the deflection of the subfloor...not the structure. When understructured add wood where there isnt...not more where there is. Might even consider going next size up on new joists and fur out the difference on existing.

    Adding a beam would,as others have said, would increase point loads where the structure underneath may not be able to support it. I don't think you want to go there.
  25. chrisasst

    chrisasst Minister of Fire

    Joined:
    Aug 13, 2008
    Messages:
    1,203
    Loc:
    cortland ny
    ok very novice here..... What do I fasten the joist to? Do I have to add more wall studs some how?

Share This Page