There are diagonal boards going from the floor joists under my sunroom to the ground. I talked to a structural engineer and general contractor and neither could explain why they are there.

Can someone help me figure out what they might have been doing? Are they to prevent sway? Is it safe to remove them?

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The framing is 16 on center and runs out from the house. Here’s the room.

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  • 2
    I would take down one of those ceiling panels or make a hole in one to check. This picture is showing the supports/what is under a room?
    – crip659
    Jun 2 at 17:42
  • Are the supports under a single joist or do the joists in that section run perpendicular to the other joists shown?
    – mikes
    Jun 2 at 18:07
  • Just added some more photos. This is under a sunroom. Jun 2 at 19:04
  • Is the structure anchored to the house?
    – isherwood
    Jun 2 at 19:33
  • I would get the/an engineer and/or builder out there to have a good look/examine the supports. I imagine you just showed them the first picture when you talked to them at the office/coffee shop.
    – crip659
    Jun 2 at 19:56

1 Answer 1


Seems fairly obvious that the framing is likely substandard on that side and this is a crude home-brew attempt to provide support, probably after alarming levels of floor movement.

You may need to remove the underfloor sheathing to permit assessing what the framing there is, and then be able to figure out what you need to add for proper support.

Or you can just yank out the supports and see if it falls down, but I would not recommend that.

  • 1
    You could deduce joist depth from exterior measurements. Joist spacing… well, maybe the spacing of the supports, or you might see nail heads at the rim. If I was a betting man, I’d say 2x6 at 24”OC. Jun 2 at 18:44

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