basement soffit - should I worry about sag?

Discussion in 'Remodel Forum & Blog' started by Hotbacon, Nov 2, 2011.

  1. Hotbacon

    Hotbacon New Member

    Messages:
    31
    Location:
    Shillington, PA
    I'm in the process of framing the soffits around HVAC ducts and plumbing in my basement using this website as a guide - http://www.familyhandyman.com/DIY-Projects/Indoor-Projects/Basement/Basement-Finishing/how-to-finish-a-basement-framing-and-insulating/Step-By-Step#step5. My original plan was to use 2x4's laid flat for the lookouts (bottom of soffits) in order to retain the most headspace in the room. However, I will have some wide soffits (mostly 4', but one at ~6') and I'm worried about sag once the drywall is installed. I have no way to secure the middle of these runs as the HVAC ducts take up the entire space.

    What is the maximum length of a flat 2x4 before you have to start worrying about sag? Would flipping the 2x4's on end be my only other option?
  2. kreemoweet

    kreemoweet New Member

    Messages:
    371
    Location:
    Seattle. WA
    Well, how much sag makes you worry? Get yourself a 4' length of 2x4 and put some weight on it - get a feel for how
    much it might "sag" under the weight of a little drywall. FYI, the big box stores have large piles of "pre-sagged" 2x4's that
    you can pick through. Get yourself some saggy ones and install them with the sag "up", so any sag from the drywall will
    bring them back down level.
  3. Hotbacon

    Hotbacon New Member

    Messages:
    31
    Location:
    Shillington, PA
    Maybe I should rephrase the question. I'm not so much concerned as to the amount of sag that will occur, as much as I am what the finished drywall will look like if the framing does sag. Therefore, will 6' 2x4 lookouts laid flat sag enough when drywall is installed to make the finished surface crack or otherwise look like crap (waves, bellies, etc.)?
  4. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I think at 6' you will be ok. Make sure to use KD lumber. I have seen an outdoor deck done with 2X4 laid flat on a 6' width. Definitely not a good plan, but all in all they stood up. A little springy depending on how you stepped. It was a little old ladies house, and I suspect the builder did it because she wanted a "look" and she only weighed about 92 pound wet. It worked for her. Anyway, the 2x did not sag from their own weight , over many years. And a little drywall may stiffen it up for you!
  5. nukeman

    nukeman Nuclear Engineer

    Messages:
    711
    Location:
    VA
    You might also look at using steel studs for this.
  6. kreemoweet

    kreemoweet New Member

    Messages:
    371
    Location:
    Seattle. WA
    If you are enclosing large hot-air supply ducts, you may well have cracking at drywall joints no matter what you do, due to
    constant large temperature swings.
  7. Gary in NJ

    Gary in NJ New Member

    Messages:
    90
    Location:
    NJ
    Isn't that the truth. You get one usable length for every 10 you touch. When I look for wood at Home Depot the pile on the floor is much larger then the selection on my cart.

    I like the idea of using steel studs and 3/8" drywall for this purpose. With such a short span the 3/8 will be fine.
  8. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Where do you find 3/8" drywall, there is no such thing where I come form.

    1/4"
    1/2"
    5/8"

    End.
  9. Gary in NJ

    Gary in NJ New Member

    Messages:
    90
    Location:
    NJ
  10. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,249
    Location:
    Land of Cheese
    Yes, 3/8" is common in the U.S., while 1/4" is not so much here in the midwest.
  11. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Doesn't suck to live in Canada when you need to visit the doctor or hospital... ;)
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