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  1. #1

    Question Engineered floor truss

    At an inspection yesterday of a town home built in the early 80’s I found these truss floor joists.

    The upper 2 X 4 members of these truss floor joists are set into masonry pockets in the concrete block foundation walls but the lower 2 X 4 members are not. They just end at the foundation wall on both the left and rigth sides and there is not a main center support beam for the span, which is pobably not necessary because of the engineered trusses (if they were properly installed) .

    The floor was found to have a moderate amount of deflection in it when walked across with heavy feet.

    I would feel that these bottom members of these truss floor joists would need to be supported in the foundation wall more so than the upper member.

    I told my client that I would look into this issue but that that a structural wall would probably need to be built under then ends of these truss floor joists along side the foundation wall for proper support.

    Any opinions or information regarding these truss floor joists and how they should be installed would be greatly appreciated. Also, I have some more pictures of them and can comment further if needed.

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  2. #2
    A.D. Miller's Avatar
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    Default Re: Engineered floor truss

    SL: Since these are engineered members a structural engineer will be required to specify the repair of this apparently abominable installation. Perhaps the addition of a metal angle on each end to support the trusses would suffice, if properly sized and fastened to the concrete block foundation walls.

    It does not appear that the upper portions of the trusses have sufficient space around them in the pockets in which they rest. That may be difficult to repair.


  3. #3
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    Default Re: Engineered floor truss

    The pictures show a top chord bearing truss. It is a correct installation.

    http://www.turkstratrusses.ca/pdf/Builders_guide.pdf

    Turkstra Trusses - Truss Downloads


  4. #4
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    Default Re: Engineered floor truss

    RA is correct. The end of the floating portion will typically be painted or have some other factory marking to show it hasn't been cut on site.

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  5. #5
    A.D. Miller's Avatar
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    Default Re: Engineered floor truss

    Quote Originally Posted by Ken Rowe View Post
    RA is correct. The end of the floating portion will typically be painted or have some other factory marking to show it hasn't been cut on site.
    KR: While RW may have posted a possible answer, I see no indication on the ends of the bottom chords that would lead me to believe these were not field modified. Additionally, and as is almost always the case, SL (as well as both you and RW) did not have the benefit of viewing the truss schedule for this house. So then, at best you are hypothesizing. At worst you are giving bad advice.

    That is why I said "Since these are engineered members a structural engineer will be required to specify the repair of this apparently abominable installation."


  6. #6
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    Default Re: Engineered floor truss

    AD

    Sorta like your comment "abominable". You did not have the luxury either to review the documents for these trusses and make the comment you did. Further you provide no documented proof. Please enlighten us further.


  7. #7
    A.D. Miller's Avatar
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    Default Re: Engineered floor truss

    Please enlighten us further.
    RW: With you, the question is: where to begin . . .


  8. #8
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    Default Re: Engineered floor truss

    I am pleased you see the humour in your faults!


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    Default Re: Engineered floor truss

    Quote Originally Posted by A.D. Miller View Post
    KR: While RW may have posted a possible answer, I see no indication on the ends of the bottom chords that would lead me to believe these were not field modified.
    AD, there is no picture of the ends of the bottom cords so of course we can't see them. However, if the original poster looked at them he may have seen the markings.

    Another way to tell if they're "field altered" is the quality of the cut. Nice, straight cuts with little tear out are most likely factory cuts.

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  10. #10
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    Default Re: Engineered floor truss

    Just curious -- Assuming that it is a correct installation of a top chord truss, do you have any recommendations for the “moderate amount of deflection in it when it is walked across with heavy feet?”

    -Jon
    Errickson Home Inspections, LLC
    http://www.erricksonhomeinspections.com

  11. #11

    Default Re: Engineered floor truss

    Light feet

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  12. #12

    Default Re: Engineered floor truss

    A strongback at midspan might help a moderate amount of deflection.

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    Default Re: Engineered floor truss

    I believe web stiffeners could be added.


  14. #14

    Smile Re: Engineered floor truss

    Wow. Thank you all for the input. I will be going back to the property tomorrow and will check the ends of the trusses for factory markings and make sure they were not altered. I’ll look into the web stiffeners suggestion to help with the deflection issue. I figured that this post would get some feed back. Thanks again.


  15. #15
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    Default Re: Engineered floor truss

    While I don't see a lot of top loading floor trusses, I have seen a few that looked just like this.
    You might be able to find a tag from the truss manf. and contact them and see if they were installed according to their specs. Though, since it was built in the 80's, this may be a dead end.

    I would steer clear of giving any kind of advice about how to stiffen the floor. Even if you are a structural engineer, I would not have that as part of my home inspection documents/service.

    When I inspect a house with trusses, I always looked for the tags that say "Bearing point here" and "Strongbacks required here". Many times those parts are missing. Of course, many times the tags are missing too.


  16. #16
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    Default Re: Engineered floor truss

    Given the age and lack of documents, you don't know whether these trusses are spanned correctly or whether the on-centre spacing is correct. In which case you may be advised to refer to an engineer familiar with this system. Contacting a local truss manufacture for advice or referral to an engineer would be a good bet.


  17. #17
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    Default Re: Engineered floor truss

    FWIW, Your pictures show a doubled top cord. I've never seen a doubled top cord that is not intended to be top cord bearing.

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  18. #18
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    Default Re: Engineered floor truss

    Ken -- have you seen many top chorded trusses like these around here?

    -Jon
    Errickson Home Inspections, LLC
    http://www.erricksonhomeinspections.com

  19. #19
    Daniel Leung's Avatar
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    Default Re: Engineered floor truss

    Quote Originally Posted by A.D. Miller View Post
    That is why I said "Since these are engineered members a structural engineer will be required to specify the repair of this apparently abominable installation."
    If no crack or damage is found on the floor trusses, I cannot understand why a structural engineer is required after the 30-years long actual live loading test was performed.


  20. #20
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    Default Re: Engineered floor truss

    Wood Truss Products

    See strongback diagram. This is an alternative bracing method, fyi.


  21. #21
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    Default Re: Engineered floor truss

    Quote Originally Posted by Jon Errickson View Post
    Ken -- have you seen many top chorded trusses like these around here?
    I've seen probably less than 300 top chord bearing trusses and less than 50 that have been altered. Very common to see in the 70's and 80's when the "sunken" living rooms were all the rage. Every one that has had the doubled top cord (that I've seen) has been top bearing.

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