Context: We are building plans for an extension to our home, on three levels. We're working with a technologist and will be getting an engineer since they have to stamp any plans. We want to have a large opening - about 20' by 20'.

Problem: For our own knowledge (we're still waiting to hear from the technologist) we want to know whether it is possible to have a T shaped steel beam supporting the 2nd floor without a post where the two beams meet. On the picture below, in yellow you'll see where I "imagine" the beams would go, and I imagine that where the yellow circles are, I need to put strong pillars that are secured in the foundation (I do have a 2nd floor that I want to build there).

Question: Is there a way to build this in order to NOT have a post where the "?" is on the drawing below?

Building Plan

  • 2
    Probably possible, but extra money and size of cross beam. Support post can covered up nicely, probably for less money. Will need local engineer to say. Local codes have last say.
    – crip659
    Feb 21, 2021 at 22:49
  • 4
    You do not want to use a beam with a T cross section. Use a I beam instead.
    – Michael Karas
    Feb 21, 2021 at 22:51
  • 4
    Just to clarify, it appears that you want to use structural steel, e.g. I-beams, that happen to meet in the shape of a "T" with support only at the outboard ends, A "T shaped steel beam" makes me think of a T-beam. It should be possible, but the beam that is unsupported at the midpoint connection may need to be quite tall to carry the load.
    – HABO
    Feb 21, 2021 at 22:52
  • 3
    Is it possible? Sure. Just tell your structural engineer that's how you want it. He'll spec the steel to support the load. You may not like the size of the resulting beam and discover that it is so tall that your 2nd floor needs a step (or 2 or 3) up, or that in order to hide it you have to have a soffit on the 1st floor so low that your kids will bang their heads on it, but yes, I'm certain it can be done. As you know, your SE will have to design this, so he's the one to ask, not us...
    – FreeMan
    Feb 21, 2021 at 23:04
  • I’m voting to close this question because this is a design question for the OPs SE, not for us.
    – FreeMan
    Feb 21, 2021 at 23:04

2 Answers 2


Can it be done? Sure. Is it practical? - you'll need to discuss with the engineer and consider the impact on your budget.

Basically you will need to increase the strength (and usually the size, to get that strength) of the beam that crosses the space so that it can support the beam going down the middle of the extension. Likewise, it will require a sufficiently strong connection to support that load, which may be more complex/expensive than simply supporting it on a post.


Yes, that connection is allowed, I have one like that above my garage door.

Basically the straight beam and the cross beam will have to be stiffer than they would need to be without the post.

This means they'll have to be taller, or be the same height and use thicker steel, so the beams will probably cost more. Indoor posts are ugly, so I think you're making the right decision to at-leas discuss this with your engineer. you may be able to save money by placing a posts at the north-east corner of "Chambre 2" (I am calling "up" "north").


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