I'm working on the design for a deck and I'll be having a long angle in it. I've used Home Designer Pro to work on the design, and it generates all the framing.

My question is concerning the beam placement and the fact that it's not in alignment with the junctions of the angled portions of the deck (circled in the image). Is this a structurally reliable placement of beams? I'm just concerned it'll be less structurally sound in these 2 places unless I move the left beam to line up with the left hand angle junction, and add an additional beam at the right hand angle junction.

Is my thinking correct here? Or will the rim joist carry the load in these portions just fine? For reference, the scale of the image is 1ft/square.

enter image description here

enter image description here

  • 2
    Realistically, you should be asking a structural engineer about this and not the internet.
    – matt.
    Commented Aug 11, 2023 at 1:41
  • As just someone who likes to over build, I would move the two centre beams to the left/long side and add another beam near the short/small section on the right.
    – crip659
    Commented Aug 11, 2023 at 11:41
  • 1
    Agreed—what you've got there is basically a longass cantilever, which IIRC is generally limited to 2' or so. I would run another beam under the diagonal edge (at least where the joists overhang more than 2' from the perpendicular beams).
    – Huesmann
    Commented Aug 11, 2023 at 12:42

1 Answer 1


Assuming that the sizes and placement of beams is right, they will be fine. I would be worried about the decking boards. What are they going to rest on? Some of them are overhanging a massive amount.

I would put a beam under them along the slope, nailed to the beams/joists shown above. It would also make it look nice from the side.

  • Thanks for the response! I like that idea, I'll add a beam along the slope. Regarding the decking timber, that isn't depicted here - this is just a layout of the beams and joists. Unless I misunderstood you? Commented Aug 11, 2023 at 0:06
  • I've added a snapshot of the 3d rendering of the deck from the underside so perhaps that will make things more clear. Commented Aug 11, 2023 at 0:16
  • 1
    I would caution taking the advice of a random, but well intentioned person on the internet, @RyanMcClure. Rohit's background is in software (as is mine), not structural engineering. I know he means well (as we all do here), but it's your structure and neck on the line, not his. This is in no way an attack on this answer or on Rohit himself, just a cautionary note to think long and hard about the source of the information you're planning to act on. I would not deign to offer an answer to this because there is (literally) too much hanging on it being right...
    – FreeMan
    Commented Aug 11, 2023 at 13:58

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