I am rebuilding my deck and have been playing around with some designs, but I've run into a snag. Where I want to direct my stairs leads directly into one of my support posts. I thought of the stair design before I realized I could cantilever the support beam. I'm sure I could eventually figure out something, but I thought I'd see if someone here had any recommendations on how to adjust my supports to not block my stairs or how to adjust my stairs to accommodate my supports.

[Edit Note]: Thank you all for the feedback and suggestions. I knew my question was subjective, so it being closed makes sense. But thank you all for the help.

Deck stairs turning into support beam

  • How about extending the deck beyond 3’1”, eliminating the cantilever, and placing the post on the outside of the stairs?
    – spuck
    Sep 20, 2023 at 4:03
  • Or adding one more landing and right-angle turn, near the bottom?
    – keshlam
    Sep 20, 2023 at 5:22
  • Are we to assume your posts are existing and cannot be moved?
    – Huesmann
    Sep 20, 2023 at 11:21
  • Build the whole deck square then pass inspection. Then put the stair case that would violate the setback.
    – Mazura
    Sep 29, 2023 at 5:14
  • I'm voting to close. There is no "correct" answer for this, it's asking for options and opinions which just doesn't fit well with the "SE way"
    – FreeMan
    Sep 29, 2023 at 11:33

2 Answers 2


That beam along the 6'-10" dimension line? Continue it along the whole length of your deck, and eliminate the beam line that currently interferes with the stairs. As drawn there's a cantilever of about 1'-6" beyond the (now deleted) support beam. Instead the framing would cantilever 3'-1". This will totally eliminate the offending post. The remaining post at the bottom of the stairs, then, also can move to a more reasonable dimension like 10'-0" instead of the 6'-1", although maybe you want that for mounting handrail.

  • 1
    Main section of deck has to be ~9.5 (9.3) feet so that one third of it can hang over 3.1 feet. "The 1/3 rule is among the common theories applied in the industry but it is not a building code. According to this rule, for every foot of joist length from the house to the beam, there can only be 1/3 of that amount overhang the beam." decks.com/how-to/articles/… ... and skip straight to 2x12s for the whole thing?... on deff no more than 16c.
    – Mazura
    Sep 29, 2023 at 5:09
  • 1
    @Mazura, I'd comfortably go more than 1/3, but exactly 1/3 sounds optimal to my intuition. Simply support a beam and cut it at center: The stresses at the center of the simply supported beam are the exact same stresses that you'll find at the support of a cantilever of half that simply supported beam's span. Ignoring complication like local buckling, the 1/3 cantilever requires the exact same joist depth as the simply supported beam. If you go past the 1/3, now the joist depth will be determined by the cantilever length instead of the simply supported length.
    – popham
    Sep 29, 2023 at 5:17
  • 1
    @Mazura, by your table, 2X10 looks adequate. The design of decks is based on 40 psf of live load which is same as a parking structure's live load. And when you use that 40 psf in design, you multiply it by 1.6 to get 64 psf. There's so much unnecessary strength in those designs that you don't need to give it anything extra.
    – popham
    Sep 29, 2023 at 5:22
  • 1
    I'm from Chicago. Unnecessary strength and decks are synonymous. So, 2x10s are okay as drawn? I'd still use 2x12s and not have to ask anybody anything... it'd be less bouncy at least. The joke has always been you can park a tank on it. But I didn't know it was actually true....
    – Mazura
    Sep 29, 2023 at 5:29
  • 1
    I couldn't get it to work. For a hot tub I sistered every joist, with new double space hangers, and put an angle brace to as far down the post as possible. Now that I think about it, x12 is for the ledgers; everything is always x10. But I don't often deal with cantilevers, and if I did that's not where the tub goes.
    – Mazura
    Sep 29, 2023 at 5:40

Depending on the size of the beam and joists, you might be able to move the vertical support a few feet away from the stairs (having the outer beam cantilevered past that support post). Or possibly bring the beam inwards to match the existing one, just with more cantilever on the wider section. Might need to use thicker joists and lower the beam a bit to accommodate the longer overhang.

If you're not set on having the stair landing at that specific height and ok with the stairs being a bit farther out into your yard, you could have the upper stairs come out a couple more steps before the landing, which would bring the stairs out some, and then you'd be fine as-is and would gain a bit more deck space.

Or, shorten up that 7' distance, loose a bit of desk area, and turn the corner a bit earlier, and have the offending post on the outside of the stair area.

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