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Double-Stud Wall for Added Structural Strength

Hammer 🔨 | Posted in General Questions on

Hope everyone is enjoying Memorial Day weekend. I’m building a partition wall under my main beam. 6 feet of the wall sits between two steel posts. I have enough 2×4 wood to build a double stud wall. I’m not thinking of this for added insulation I’m thinking just to include as added support for the house. Like a why not scenario if I’m already making a wall might as well add some strength. House is old so is settled. Not sure if I should go out and get 2×6, 2×8 or is a double 2×4 wall just as good. Don’t want to go through hassle of returning wood when I already have it. OTOH is building a thicker wall pointless

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  1. Expert Member
    Peter Engle | | #1

    If the house is old and the main beam is noticeably sagging, adding some support under it can help quite a bit. How much depends more on the quality of the concrete floor than the wall framing - if the floor can't take any loads, more lumber won't help (much). If you think the floor is pretty solid and you've got the lumber to spare, I would just double up the studs rather than making the wall fatter. Doubled 2x4 studs are stronger in compression than 2 studs set edge to edge, because of better buckling resistance. It would also just take up less space in the room.

  2. Expert Member
    Zephyr7 | | #2

    +1 for doubling studs up (making them like posts) instead of making a fat wall. Loads travel in straight vertical lines here, and the strongest support doesn't try to "bend" those lines -- which would be the case if you built a double stud wall with the studs on either side of the beam instead of directly beneath it.

    Slabs aren't as strong as footings though. You can transfer some load to the slab, but if you really need strength, you'd need to either build a footing or a pier (or several piers). If you have a lot of sagging, my recommendation would be to cut out a hole in the slab at the mid point of the span of the beam, then build a concrete pier there to handle load. Put a good post (which could be several sistered 2x4s, or a column built up of 3-4 2x6's) on top of the pier. This would make the pier the load bearing part, and the rest of your wall would just be a non-load bearing partion wall.


  3. Expert Member
    Malcolm Taylor | | #3


    This may well be a solution in search of a problem. The best way to address possible structural issues is to identify the weakness and address it. Unless there is some reason to believe the beam needs additional support, there isn't much point in adding it - and certainly no reason to go beyond a conventionally framed stud-wall, which would be what you would replace that beam with if it were being removed.

  4. Hammer 🔨 | | #4

    Thanks for all the replies. I have several steel posts on footings in place and floor does not have any sagging issues. I have the additional lumbar and although lumbar is expensive doubling up studs on a small wall will cost me up to a $100 at most. Is it needed, probably not but if it doesn't do more harm than good I don't see why not. The posts will be visible on one side of wall. In case anything were to start failing I feel like it might show signs before completely collapsing. It might be pointless maybe but it may make me feel better at night.

    1. Expert Member
      Malcolm Taylor | | #5


      Fair enough I guess. Ask yourself though: Originally, if they had decided to put a wall there instead of a beam, how would it have been built? Most likely a 2"x4" wall @ 16" oc.

    2. Expert Member
      Zephyr7 | | #6

      Load bearing walls are typically just "regular" stud walls. You usually only beef up things at columns and the ends of headers, where you have concentrated loads. In my earlier comment, I had just meant to point out that walls with sistered studs are stronger when supporting a beam than a wide stud wall is. The best solution is either a regular wall (which would need a footing to carry a load properly), or a column with a pier (which is probably easier to add as a retrofit).

      If you want to frame out the wall directly on top of the slab, I don't see a problem doing that, just know that the slab alone isn't really a proper way to support stuff. Since you already have adequate support for that beam, your wall is just a supplemental structure and shouldn't cause any issues.


  5. Walter Ahlgrim | | #7

    Is this question about the same beam as your other question?

    That beam needs to have the failing wall it rests on repaired.

    Sure you could put a wall under it but you have no idea what you are building on. The slab under the wall your new wall is likely to be very thin with no base gravel under it making it poorly suited for supporting large loads.


  6. Hammer 🔨 | | #8

    Hi Walta this is a different wall then the one in my previous post. I have this beam sitting on footings. The one I need to place new footing on intersects this wall. If the pictures make sense where you see plumbing drop down from ceiling is in between my posts on footings. This is my main beam, I wanted to add a few double 2x4 here for extra support. The double 2x4 Hail Mary post in second pic runs to foundation wall. I will probably need 1 or 2 new posts here with footings to be safe. This is the wall I was wondering if I could put a header in but I don’t know how much weight it is supporting so I will put new posts. Anyone know how to make new footings without a concrete saw? I have a circular saw and miscellaneous tools.

    1. DCContrarian | | #9

      I've used this blade in a circular saw to cut through a slab:

      Go slow, cut about 1" deep at a time, and have a helper pour water into the cut as you go to keep the blade cool and the dust down. And wear hearing protection, eye protection and a dust mask. But it should only take a few minutes. If you can't get the piece out, do another cut about an inch inside the first one and bust up the 1" piece with a hammer, then you can get a prybar in there and pry it out.

      1. DCContrarian | | #10

        You can also rent a concrete-cutting saw but for this job it's probably overkill.

  7. Hammer 🔨 | | #11

    I will try it out. I remember years ago outside I used a hammer drill and drilled holes in a square. Then sledge hammered it and the concrete cracked in line with the holes. Not sure if this would be harder or easier. I suppose I would need engineer specs but what size and depth is the hole typically for the footings?

    1. DCContrarian | | #12

      The way a footing is engineered is first you figure out how much weight it needs to hold. Then you figure out the bearing capacity of the underlying soil, which will be in pounds per square inch. With those two numbers you can calculate how many square inches the footing needs to be. There is a formula for calculating the thickness based on the area but I don't know it offhand. I do know the bigger the footing the thicker it needs to be.

      In some places the local code specifies that you can presume a minimum bearing capacity for the soil, in others you have to have a soil test done.

  8. Walter Ahlgrim | | #13

    When I look at photos number 1 and 2 nothing jumps out and makes me think this beam needs help. When

    I look at image number 3 I see the same images from your previous question and I still think the best course of action is to have the wall under the beam rebuilt so it will carry the load as intended originally.

    I like DIY projects more than anyone but when I look at photo #3 it screams to me call in the mason and pay his bill.


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