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Community and Q&A

Easiest way to frame interior walls on slab

brettske | Posted in General Questions on

I am building a house with double wall construction. Exterior 2×6 wall is framed. It is a slab on grade home and there is some unevenness in the floor. Trusses will be delivered soon and I worry about having interior non-bearing walls sticking up too high and causing problems for trusses that are designed to span from exterior to exterior….no interior bearing walls.

Should I:
1) Frame all the interior walls a bit shorter and frame interior walls before setting trusses
2) Frame with the standard 9 foot trusses and notch the tops of the studs that are too high where the trusses will cross.
3) Set the trusses first, and frame interior walls later
4) Or…….

Thanks for any help or suggestions you may have!

Moses Lake, WA

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  1. Expert Member
    ARMANDO COBO | | #1

    Frame all your interior walls first. Typically, all trusses designed for bearing from exterior to exterior have a crown, so they "flatten-down" after you install weight on the floor or roof trusses; hence the use of Adjustable Truss Clips on top plates, designed for alignment control and to allow the bottom cords to slide down.
    I specify Simpson Connectors, and usually are DTC, STC, STCT and HTC depending on design loads, but you may want to contact the truss manufacturer and find out if you are required to use clips and which clips kind. Sometimes we install them just because is a good idea on long spans.

  2. Expert Member

    The solution really depends on how bad the irregularities are. As Armando said, the trusses can handle minor variations in wall height. But much higher interior walls can make setting the trusses at all very difficult. You may not be able to get them down to the exterior walls, and in trying are introducing forces onto their webs they are not designed for.

    All the solutions have up and downsides:

    - Varying the stud lengths is time consuming and means your interior walls will have varying heights. The lower sheet of drywall may not fit and have to be cut down.

    - Notching the upper plates causes problems where the walls are parallel to the trusses. Blocking for drywall-backing on top of these walls will be higher than the nearby trusses making the wall/ceiling intersection difficult.

    - Adding a thin top plate to the exterior walls solves the truss problems, but means the higher walls now leave a larger gap between the bottom sheet of the drywall and the floor.

    If it were me I'd probably opt for #3.

  3. mchis | | #3

    # 3 option is correct . Set the trusses first .

  4. Expert Member

    Just to clarify, I meant I'd opt for my option #3. Framing interior walls after the trusses are up is very time consuming and makes bracing the exterior walls a lot more difficult.

  5. Jon_R | | #5

    Don't these adjustable truss clips encourage a crack between vertical and horizontal drywall? Or is ceiling drywall not used as an air barrier?

  6. Expert Member

    Truss clips connect the interior walls to the trusses and allow them to move seasonally. Manufacturers do not allow the trusses to be fastened directly to the framing as you can damage them or even lift the interior walls. Potential cracking at the wall/ceiling intersection is dealt with by keeping fasteners back 16" and using drywall clips. If there are enough interior walls to brace themselves, some builders don't connect them to the trusses at all.

  7. brettske | | #7

    Thank you for your help on this question. I think I will go ahead and frame interior walls first but add a 7/16 or 1/2 cap of plywood/osb to the exterior wall plates to add some height over interior wall irregularities. Does OSB/plywood have sufficient strength to withstand compressive forces of trusses?

  8. Expert Member

    Yes either will do.

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