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Thread: Solution To Home Floor Joist Deflection?

  1. #1
    Associate Engineer
    Join Date
    Dec 2020
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    3

    Solution To Home Floor Joist Deflection?

    Hello,

    I am the owner of a home that has very noticeable deflection/bounce in the flooring system. It is a newly constructed home and the builder, his architect, his framing contractor, and lumber supplier can't explain why. I consulted with a local structural engineer and he even said he is not seeing anything on the home's plans and drawings that stand out to cause the major deflection or bounce. Home is built to code. In his defense, he did state that he typically does not work in the residential space and recommended I seek a better expert that deals with my issue.

    To summarize, nearly half of the 2x10 floor joists were sistered with 2x10 floor joists. Glued and nailed. Wood X bridging and solid 2x10 blocking in between floor joists. Steel post and beam in the center of home's foundation. There was an improvement after that work was completed. But, my 60 pound dog can still make the floor deflect and make dishes rattle when trotting by. The home has a poured concrete foundation and full basement.

    I have been searching the internet for solutions and came across a few ideas, but it is difficult to know if any option will solve my problem of providing a very solid feeling floor with little to zero deflection. Some options I see mentioned are:

    1. Sistering of joists - [B][U]this has been completed[/U][/B] and the results showed an improvement, however, does not meet my standards of a solid feeling, little to no deflection floor system.

    2. Remove wood X bridging, replace with wood 2x10 solid blocking every 1/3 of the joist span. Glue and screw.

    3. Remove wood X bridging, replace with metal X bridging

    4. Attach a wood 2x4 or 2x6 piece of lumber to the bottom of every joist to form an inverted "T" the entire length of the joist. Glue and screw. This will increase the depth of the joists and provide strength.

    5. Attach a piece of 0.25" to 0.5" flat stock of cold rolled steel the entire length of the joist. Holes must be drilled in flat stock. Glue and screw.

    6. Attach 0.75" plywood sheet to the bottom of floor joists creating a ceiling in the basement. Glue and screw. I do not like this idea because the basement will be a finished living space in the future.

    7. Add more steel posts through out basement - I do not like this idea because the basement will be a finished living space in the future.

    8. Attach perforated steel strapping the entire length of joist one half on one side and one half on the other side. Nailed.

    9. Attach 1x3 wood furring strip perpendicular to the floor joists. Glue and screw.




    What are my options to make the floor system very close to zero deflection? Is there a proven option that will solve my problem?

    I can provide specifics if needed to assist in solving this problem.

    Thank you very much.

  2. #2
    Principle Engineer
    Join Date
    May 2015
    Posts
    208
    Span? 16' is about max span for a 2x10 check the tables and the grade stamp on your joists. Some codes allow floor sheathing which is pretty thin and the deflection will vary with the cube of the thickness. Solid blocking is now code in many places.

  3. #3
    Principle Engineer Cragyon's Avatar
    Join Date
    Feb 2013
    Location
    Newark, NJ
    Posts
    279
    "Home is built to code."


    Assuming you can see the wood structure I would put eyes on the actual deflection in action.. Get some well fed friends or what ever and have them walk the floor and observe and determine the area and structural members deflecting..

    Could be manufacturing defect, wood defect, fastener defect, or not actually built to code. When you see the deflection area or component in action then get a plan to stiffen or repair.

    Throwing wood and effort at it without factual information is likely to waste your time and money.

  4. #4
    Associate Engineer
    Join Date
    Dec 2020
    Posts
    3
    Quote Originally Posted by Hudson View Post
    Span? 16' is about max span for a 2x10 check the tables and the grade stamp on your joists. Some codes allow floor sheathing which is pretty thin and the deflection will vary with the cube of the thickness. Solid blocking is now code in many places.
    Span is approximately 15' from rim joist/foundation to the steel I-beam

  5. #5
    Associate Engineer
    Join Date
    Dec 2020
    Posts
    3
    Would the option circled improve the [B][U]already[/U][/B] sistered joists from up and down movement?
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