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I have an 8x10 stick build shed with trusses 16 inches on center. I would like to remove the bottom chord of one of the trusses one third of the way into the shed so that I can get better access to the loft area up top for storage.

Is there additional bracing I can add to bring back structural support? The shed is overbuilt for our snow and rain conditions in Virginia. Thank you for your help.

view looking up at roof trusses

view from outside the shed

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  • I would be more tempted to create an exterior access door and put 1/2" plywood on the trusses so you can load/unload from the front.
    – UnhandledExcepSean
    Commented Dec 5, 2023 at 15:13

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This is a tiny shed with a steep roof pitch (and therefore less spreading force). You absolutely do not need all those trusses, especially at the smaller than normal spacing.

Many such sheds larger than this have been built with simple rafter roofs and no rafter ties and they're standing just fine. Even with one rafter tie this shed won't budge. A wall span of less than 10 feet will not bow substantially.

Go right ahead and remove one bottom chord, or even every second one... or even all but one. No need to waste time and materials rebuilding it to Soviet bomb shelter standards. It'll still be rock solid.

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Under gravity loading the obstructive truss bottom chords are tension members. If you install a framed opening through one or two, toe nails or joist hangers will be insufficient to substitute for the tension strength of continuous 2×4s. Additionally, severing the tension members between vertical web members basically forms a see-saw hinged at the base of the vertical web members. Severed bottom chords, then, also need vertical support.

Rather than analyze the thing to death, the DIY way is to to follow the IRC's floor opening strategy by building sister trusses beside the trusses at both sides of the opening. Since you'll be installing 2 trusses, you can remove up to two trusses for a 32" or 48" wide opening.

  • First remove one or two trusses to make space for your opening.
  • Now span 2×4s perpendicular between the trusses and spaced every 12". These hold up the roof that the removed trusses were supporting (they should be oriented with the 1-1/2" face touching the roof surface, where you should add an adhesive since you wont be able to nail down the roof sheathing again). Face nailing with 3 10d common nails at each connection is plenty.
  • Now build the sister trusses on the other side of the supporting trusses. Install OSB spacers between them and nail them together every 12" with 10d common nails.

framing

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  • Thank you for the detailed comment. I've read it five times, trying to digest and visualize it. This has been my first big project so I'm still learning. Would you happen to have a picture or diagram of the supports. If it matters any, I will only be removing one bottom chord. Thank you again.
    – Mike H
    Commented Dec 5, 2023 at 4:51
  • @Mike, image added. It's basically studs spaced every 12" with the top chord of trusses at the sides acting as top and bottom plates. For installing each one, I would screw a chunk of OSB to the underside of the top chords to provide a shelf holding the block tight to the roof sheathing.
    – popham
    Commented Dec 5, 2023 at 6:37
  • This is absurd. The shed is 8x10, for crying out loud. You could remove half the trusses and nothing would change. You could cut out all the bottom chords but one and nothing would change. Do not waste time, effort, and resources rebuilding this as though it was a McMansion.
    – isherwood
    Commented Dec 5, 2023 at 14:47
  • @popham, I appreciate your knowledge and engineering approach, but at some point real-world conditions become so far afield of the scenario that knowledge was meant to address that they're just silly. This is one such case. It's economically and environmentally irresponsible to suggest that someone undertake what you've proposed.
    – isherwood
    Commented Dec 5, 2023 at 14:57
  • @isherwood, I'm almost on board with you. That roof sheathing, though. 5/16" has a span rating of 16/0 (3/8" is good for my region's 30 psf snow load), and I don't trust the load path from your rafters down to the wall's top plate. Looking at the 1st image again, I can see one of the bearing points in the bottom right corner. That looks okay from what I can tell. I anticipated the OP ignoring the part about constructing 2 additional trusses. I figure that cutting up one truss is more than half the material. A home inspector would flag your solution, but not this one.
    – popham
    Commented Dec 5, 2023 at 15:44

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