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I'm building a garden shed with 2x4's and have some roof overhang on the sides. Due to an inadequate design, exacerbated by a change in the design on the fly, the overhangs are slightly bending downwards.

Overhang bends downwards

The problem is that the overhang is only attached to the outermost roof beam, which pulls the beam down and sideways, out of plumb thereby causing the overhang not to be level with the rest of the roof. Design view

I've tried solving the issue by fixing the beam to the top plates with more screws and a metal fastener, but the problem persists. Metal fastener

Any ideas on how I can fix this issue?

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    That's a bit of a design fail. It's all 'lever' & no 'canti'. I could see that eventually slumping so far as to fall off. The wall plates should really run right through, not just be 'draught excluders' between ceiling joists. How far do you want to take it apart to fix it? What's the roofing made of [how heavy]? Does the ridge board at least run right through. Is it substantial enough to fully support the rest? How do you feel about corner pillars? 45° supports?
    – Tetsujin
    Apr 13, 2023 at 9:00
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    On the first photo, the pair of "top plates" seems to be bowed downward a bit.
    – Armand
    Apr 13, 2023 at 10:41
  • Good eye, Armand. I hope that's an optical illusion. It's quite severe, otherwise, and brings into question the integrity of the project at large.
    – isherwood
    Apr 13, 2023 at 18:27

3 Answers 3

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It looks like you have a metal roof, so there is not much weight there. You have 2 choices:

  1. Remove the roofing and roof decking back far enough to access the second rafter in. Build a "ladder" for your end rafter and facia with 2x4s perpendicular every 2 feet. Build up your end wall so the angle is filled in and the ladder has something to sit on. Finish the roof. I attached a pic with my idea very poorly drawn in. The blue and yellow show the ladder the black is the rafter that is eliminated and then filled in with blocking. ( not an artist obviously)

Roof

OR

  1. Add a couple of braces from the facia board angled to the wall for a little more support. Attach at the vertical wall studs not into the OSB. Roof is not heavy this will help with sag.
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    #2 for the win. (I’d have a different opinion if the roof wasn’t already on.) Apr 13, 2023 at 14:10
  • That's a good idea (the sketch), and I'd probably add a top plate flush with the roof stringers—plus studs to fill (why the heck aren't there any? is that space intended for windows?) for support.
    – Huesmann
    Apr 13, 2023 at 14:50
  • I believe what OP has is called an outrigger. What I did on my roof deck for that was 1) lay the 2x4's that support the outrigger fascia board on their side, 2) notch the last rafter so that the 2x4's are recessed into the rafter and their tops are flush with the rafter and 3) carry the 2x4's back to the nest rafter and fasten then there. Basically create a low load bearing capacity cantilever.
    – SteveSh
    Apr 13, 2023 at 18:56
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    While your suggestions will likely help with sag, I fear up-lift from winds will need to be accounted for as well. The extension should be anchored to the top of the wall and not just blocked along that dimension.
    – psaxton
    Apr 13, 2023 at 19:40
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I see two fairly simple fix options.

  1. Add two steel gussets to the faces of the framing. 1/4" by 3" bars about 6 feet long, fastened with countersunk flathead screws, would properly support the outboard subfacia (fly rafter) at each end. That would resolve 95% of the problem.

enter image description here

  1. Remove the two end pieces of roofing steel temporarily and run the purlins straight through. They alone would support things fairly well. Add extras in that area if you like.

enter image description here

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Why not use a lolly column to move the frame up a tad, and a 4x4 at an angle into the wall. Garages in my area all support their cantilevered roofing members like this sometimes by running the 4x4 down to the foundation. If you don't have a column handy, all you need is a car jack, a 2x4 for the functional equivalent. Then decide your angle and get out your rafter square. There's no prohibition of using structural members that aren't horizontal or vertical. ;)

EDIT: Added two shots of garages in my neighborhood. If you build a "triangle" in the right dimensions, then siding (if you're using vinyl siding) will install nicely if the length of the member that's fastened to the house is a multiple of the width of your siding. Simply side up to that board, and then go shorter starting with the next row upwards. My thinking is if you're going to build the shed once, don't use dubious halfmeasures like gussets and cleats or whatever. Do what professional carpenters do when they build small structures. $0.02

enter image description here

enter image description here

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  • That's going to be fairly expensive (It wouldn't be a 4x4, but many) and has significant ramifications for siding.
    – isherwood
    Apr 13, 2023 at 18:24
  • @isherwood Uh... that doesn't seem accurate. Look at his picture. The length of backside looks to be a trade-sized sheet of OSB. 8'. You would only need a support on either side tied into the studs, and certainly not to the base of the shed. With supports at 45 degrees on the backside would be x-x-x√2 which on a 2' overhang is only 2'5 feet. And significant ramifications is a C-section. Cutting some vinyl siding around those two supports is significantly less ramified than you claim. Honestly, the OP could get away with a length of 2x4 which at a few bucks a board is trivially cheap.
    – J D
    Apr 13, 2023 at 18:55
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    Like I said, I could take a walk and find half a dozen garages cantilevered this way.
    – J D
    Apr 13, 2023 at 18:57
  • Opinions vary. You did say 4x4.
    – isherwood
    Apr 13, 2023 at 19:04
  • @isherwood They do, and I did. He does look like he's got some 2x6's sistered there on the eave in his inventive cantilever so it would pair up nicely, and since it's an outdoor application, it's easier to weatherproof with paint. But, he could do the same with sistered 2x4's or 2x6's from scrap too as long as he used a health dose of caulk...
    – J D
    Apr 13, 2023 at 19:22

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