We are remodeling the first floor in our 2 flat. We use it as a single family. Tearing out a wall between kitchen and "second" bedroom from when it was originally built in 1926. The current floor joists are 2x8 and span the 24 feet, but there is a wall mid way. If we were to double up the joists to add additional support would that work? These are 16" on center. We have steel columns in the basement supporting the house. Or do we need to do a header to support the second level? Any help would be greatly appreciated.

  • Wow, 2 x 8's 24' long. They don't grow 'em that long anymore.
    – Lee Sam
    May 2, 2017 at 3:30
  • Where is this property located? Lee Sam evidently understands the nature of this structure, but interested others may not; I don't. Could you give more detail and context? I gather that a "2 flat" being used as a "single family" must be what I always heard called a duplex. But are the two apartments side by side or one at ground floor and one at 2nd story? Are there or were there originally two kitchens? Have you already removed the wall between kitchen and bedroom? May 2, 2017 at 9:47
  • One on top of the other....there is a kitchen above.....we were hoping to make the span, but the original header sounds as though it will be the only way to go at this width...we have not removed the studs yet, as our engineer will not be here until tomorrow...trying to get options... May 2, 2017 at 13:13
  • Depending on the location this sounds like it could be a valuable property. (I know of a case where 4 people bought an old upper-lower duplex in Cambridge MA for $1M. You don't want to mess this up. The value of the property in a future sale could vary greatly depending on what you do. May 2, 2017 at 13:48
  • What is the layout in plan view? This wall dividing kitchen from a bedroom that you want to remove, is it to make the kitchen open plan with a lounging area? convert the bedroom to a lounging and entertainment area open to the kitchen? Is this a load bearing wall? Is this wall parallel to or perpendicular to the mid-span wall supporting the ceiling joists and which is supported below by steel columns in the basement? May 2, 2017 at 20:25

2 Answers 2


No, you cannot span 23 feet with conventional lumber, even doubled. It'll be as bouncy as a trampoline and won't meet code, and that's if you can find such lengths.

You'll need at least a 12" (nominal) I-joist or an engineered floor truss to span that far, or you'll need an LVL or steel beam midway.

None of us can offer more specific advice without a site visit, and most of us aren't engineers anyway. There's really no way around having a qualified local expert stop by.


Way back then, the wood was milled to 1 5/8" wide to 7 5/8" high. You say there is a wall "mid-way". Therefore, the span is 12'. So, with joists at 16" on center, they will support about 78 lbs. per square foot. (This is based on a No.2 grade Douglas Fir-Larch wood joist. Douglas Fir-Larch lumber is some of the strongest. So, a couple of factors to consider: 1) If the sources of wood is something other than Douglas Fir-Larch, then it could be up to 10% less, and 2) if the joists are fairly "sound" (fairly straight grain, without a lot of knotholes , without loose or missing knotholes, etc.), then the strength could be up to 25% - 30% more.

Assuming a "Dead Load" (subfloor, underlayment, the joist themselves, finish ceiling below, and carpet or other finished flooring) of 15 lbs. per square foot, then that leaves a "Live Load" of 63 lbs. per square foot.

The Code requires a live load of a minimum of 40 lbs. per square foot. However, at 40 lbs. per square foot, the floor will "feel" springy. We like floors designed to 75 lbs. per square foot, so the floor feels "stiff".

Other issues to consider: 1) will there be a water bed, 2) will there be a large refrigerator, 3) will books be stored in the rooms. (The Code requires a live Load for book storage of 200-250 lbs. per square foot. Other storage is 125 lbs. per square foot.) If any of these conditions apply, I'd add an extra joist in those areas.

Also, the mid-span wall must be supported down to the footings. You say, "there are steel columns supporting the house in the basement." That's good, if they support a large enough beam under the mid-span wall above. To calculate this, we'll need to know the size of the beam under the wall and how far the columns are apart.

  • Wood floors and tile above this area. Eventually we will move and rent out both units, so we want the option to reuse the upper level with a full kitchen. May 2, 2017 at 13:15
  • Does the upper level have a full kitchen right now? May 2, 2017 at 20:44
  • @JimStewart Hmmm...I don't know. For loading capacity, the code doesn't make a distinction. However, I've found that a few items in a house need special attention: (I.e.: refrigerators, waterbeds , etc.) were
    – Lee Sam
    May 2, 2017 at 21:57
  • Were you thinking of other things...?
    – Lee Sam
    May 2, 2017 at 21:57
  • I was just wondering how changing the room allocation would affect the use of the structure. I was thinking about what this meant about how we live now compared to the 1920s when this structure was built. Wondering if it was worth the effort to change it, I guess. The OP reported they use the two units as a single family dwelling. I was wondering about the details of that. May 2, 2017 at 23:19

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