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Old 04-26-2020, 10:11 AM   #16
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Re: Shed / workshop framing design--is it too ambitious?


You might wanna check ASCE 7-05 with all that overhang area and steep angle.
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Old 04-26-2020, 11:04 AM   #17
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Re: Shed / workshop framing design--is it too ambitious?


I'm not really fond of that rework of the roof framing. You've doubled the effective overhang on the sides, which are supported almost entirely by fascia or rim boards on the front and the back edges. (The short ones in the overhang are not continuous, so they contribute very little to support of the overhang) You should have rafters that run front to back as far out to the end of the wall as you can get them, to shorten the cantilever supported by the fascia. You may need to double up those rafters, since they essentially support the entire cantilever.

It might look odd visually, but structurally the best way to support the cantilever is with beams running along the top of the front and back walls, extending out to support the outside rafters. It's similar to your original framing, except the beams can be as deep as you need them without raising the roof off the walls.

Similar to how it's better to have the tie-down points of the wall farther apart, deeper beams are stronger than wider beams of the same (or even greater) volume. For instance, in the strong direction, a 2x6 is stronger than a pair of 2x4s side by side.


You need to follow the load path, i.e. where doe the weight of, say, a couple of feet of snow go? It goes to the deck first, then to the adjacent rafters. From there it goes to whatever supports those rafters, and so on. In the case of the reworked framing, a load on the outer 2' of the cantilever goes to the edge rafter, and then to the corners, where all the load is concentrated on the end of the fascia board. From there, it flows to the next rafter and down that next rafter to the wall. So, all the weight applied to the outer 2' of the roof on the front half of the roof is carried by the edge rafter as a simple span, the cantilever of the fascia board, and then the cantilever of the next rafter. The longer the cantilever, the more stress in the boards.
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Last edited by HotRodx10; 04-26-2020 at 11:25 AM.
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Old 04-26-2020, 11:33 AM   #18
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Re: Shed / workshop framing design--is it too ambitious?


Quote:
Originally Posted by brentron View Post
Hi Neal, I reworked the designs a bit, is this what you're suggesting? With this design, it looks to me like the long front overhang (the high one) doesn't have enough support since it's missing a whole rafter.
If you turn the 2x4s on the flat you can put a 2x6 rafter under them on the outside of the wall..
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Old 04-26-2020, 11:52 AM   #19
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Re: Shed / workshop framing design--is it too ambitious?


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Originally Posted by HotRodx10 View Post
You should have rafters that run front to back as far out to the end of the wall as you can get them, to shorten the cantilever supported by the fascia.
I'm not sure I understand what you're saying here. Do you mean the way I had it originally? Are you thinking of the front as the side with the portal opening or the side with the small door? We might be thinking of this 90˚ off from each other, which is maybe why I'm confused. I think of the high wall as the "front."

Quote:
Originally Posted by HotRodx10 View Post
You may need to double up those rafters, since they essentially support the entire cantilever.
Slightly confused by this too... the way I see it, the rafters are the cantilever. Or do you just mean the whole part of the roof that sticks out is the cantilever? In any case, I definitely have been worried about having enough strength in the rafters for the cantilevered overhang (the high end, which I think of as the front.)

Quote:
Originally Posted by HotRodx10 View Post
It might look odd visually, but structurally the best way to support the cantilever is with beams running along the top of the front and back walls, extending out to support the outside rafters. It's similar to your original framing,
I'm missing how that's different from my original design.

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Originally Posted by HotRodx10 View Post
except the beams can be as deep as you need them without raising the roof off the walls.
If they're on top of the walls won't any height raise them off the wall?
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Old 04-26-2020, 12:00 PM   #20
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Re: Shed / workshop framing design--is it too ambitious?


@HotRodx10 In thinking more about your post and trying to understand, I put together another design to see if I can capture what you're saying. Is this what you're saying? Putting a 2x10 (or 12 or whatever) on the face anchored into the top, rather than actually sitting on top of the top plate?
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Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-26-12.56.34-pm.png   Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-26-12.56.47-pm.png   Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-26-12.57.15-pm.png   Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-26-12.57.42-pm.png  
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Old 04-26-2020, 12:11 PM   #21
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Re: Shed / workshop framing design--is it too ambitious?


Quote:
Originally Posted by Nealtw View Post
If you turn the 2x4s on the flat you can put a 2x6 rafter under them on the outside of the wall..
Like this?
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Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-26-1.06.26-pm.png   Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-26-1.09.29-pm.png   Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-26-1.10.01-pm.png  
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Old 04-26-2020, 12:42 PM   #22
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Re: Shed / workshop framing design--is it too ambitious?


Quote:
Originally Posted by brentron View Post
Like this?
That would do it.
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Old 04-26-2020, 03:50 PM   #23
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Re: Shed / workshop framing design--is it too ambitious?


Quote:
Putting a 2x10 (or 12 or whatever) on the face anchored into the top, rather than actually sitting on top of the top plate?
Yes, that's what I was proposing.


The only thing I would suggest for that configuration is to extend the studs up and just put top plate, as would be typical for a wall. The rafters would bear on the inside edge of the top plate and the top edge of deeper beam on the front, eliminating the the beam you have on top of the studs. The deep beam attached to the outside of the wall functions as a header over the windows and a support for the edge rafters.

In order to keep everything flush for the window frames, you could add 2x's flat the rest of the way around the windows and bring the face of the wall out to the outside face of the deep beam. At the top of the portal opening, you could bring it back in that 1 1/2", or shim out the wall as well.
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Old 04-26-2020, 04:55 PM   #24
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Re: Shed / workshop framing design--is it too ambitious?


Too lazy to read everything.....but the FIRST THING that I thought was “That’s a lot of work”.....and the SECOND thing was “he’s going to be sorry he didn’t make it bigger after using it for a week”. Years back poured a 16x16 slab on grade and built a two story “workshop” and “tool storage” deal on it. Building now houses my wife’s pottery studio on second floor, and her showroom on the first. The two “additions” (8x16 shed roof on each side) hold stuff like tiller, chain saws, garden tools, z-turn mower, ingersoll 4018 tractor, push mower, weed whacker, drag chains, come alongs, smaller ladders, etc. etc. to the point it don’t all fit. Workshop? Now over my garage for light stuff, and in my garage for 10” and 12” slide compound miters, 3 hp cabinet saw, radial arm, compressors, dewalt jobsite 10” table saw, 6” jointer, router table, thickness planer, and my highlander and Tacoma (which obviously have to move out when the power tools come out). Anyway, if you are in a “forever home” you’re gonna accumulate a lot of stuff. My advice fortune out what up need, double it, build the frame and do the finishing stuff later if you need to save $.
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Old 04-26-2020, 07:43 PM   #25
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Re: Shed / workshop framing design--is it too ambitious?


Don't know where you are at and anything other than overall dimensions so can't speculate on wind, seismic, or snow loads.

I like the idea of getting rid of the 6x6 cantilever as the thread has turned.
Check to make sure you don't have a restrictive height for sheds.
Don't know what the man door is in comparison to the front slider or barn door (or is it open for a stage?), but continue the walls up to roof.
I'd put the header above the windows, depending on what you are doing for the opening under that it can be just a mullion.
Ditto on eliminating the cross braces for bracing, each of those connections would become critical in serving that purpose. Sheathing, or upping the ante to a portal frame and extending the header with the sheathing.
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Old 04-27-2020, 01:53 PM   #26
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Re: Shed / workshop framing design--is it too ambitious?


So now I'm really unsure of how to move forward. The two alternative approaches that I've been given both require me to reduce the strength of the rafters.

First, following @HotRodx10 's suggestion to fix a deeper 2x into the top plate on the face. What I don't like about that is it requires making the birdsmouth cut longer, out past the end of the top plate (and by extending the birdsmouth cut, effectively reducing the strength of the rafter at the most important point for the cantilever.

Also, I'm not sure about a header not actually sitting on anything. Just nailing it in sideways really doesn't seem sufficient.

The reason I originally thought of a 6x6 purlin on top of the top plate was to avoid just both of those issues.

One solution I can think of : cut a lap out of the studs and top plate (which is 2x6 anyway so it would just become a 2x4) to make room for the deep beam. (See attached screenshots.)

I could also move the beam to the inside rather than the outside because (again) I want to reduce how deep the birdsmouth in the cantilevered rafters. So I want to cut the birdsmouth as if it's a 2x4 top plate even though it's technically a 2x6 top plate. What do y'all think?
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Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-27-2.33.00-pm.png   Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-27-2.33.18-pm.png  
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Old 04-27-2020, 02:11 PM   #27
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Re: Shed / workshop framing design--is it too ambitious?


The second approach in this thread that came up was @Nealtw 's suggestion to build a ladder rake overhang supported by the side wall.

This requires removing or notching a rafter, which I don't like.

However, I did see an idea on the internet herethat would solve that though, using tension ties to connect blocking through a rafter.

Since I'll be using 2x8 blocking for the ladder, a tension tie on the top would prevent sag and have ~7 inches of room for the weight to crush together into the rafter.

Actually, almost the same thing could be accomplished with a strap going across the top. I wonder if there is other hardware (e.g. elbow connector) that I could use to further help connect the forces through that rafter.

I like this idea, assuming it would work, because it doesn't remove as much strength from the rafter.
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Old 04-27-2020, 02:35 PM   #28
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Re: Shed / workshop framing design--is it too ambitious?


Quote:
Originally Posted by brentron View Post
So now I'm really unsure of how to move forward.
2' overhang? Framing in Post #21 is fine. Don't forget you have 8' staggered with 4' long sheathing on top. And I assume a 2x fascia (or subfascia).

Any 'modern' design, even for a shed, requires a lot of extra detailing. Most people who are keen on that style feel the trouble is worth it.
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Old 04-27-2020, 02:48 PM   #29
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Re: Shed / workshop framing design--is it too ambitious?


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Originally Posted by 3onthetree View Post
2' overhang? Framing in Post #21 is fine.
Yes, I'm not worried about the 2' overhang with the framing in post #21, I'm worried about reducing strength of the cantilever for the 4' overhang on the front. By notching that rafter (which is already notched with a birdsmouth cut on the other side) it's significantly reducing its effective strength.

This means that the 4' cantilevered overhang of 8' thick wood, plus decking, underlayment, shingles, and fascia is supported by a beam 4 3/8" thick. Only 3 5/8" if I do the full 6" birdsmouth since I have a 2x6 header.
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Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-27-3.47.10-pm.png   Shed / workshop framing design--is it too ambitious?-screen-shot-2020-04-27-3.58.46-pm.png  

Last edited by brentron; 04-27-2020 at 03:02 PM. Reason: add link
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Old 04-27-2020, 03:08 PM   #30
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Re: Shed / workshop framing design--is it too ambitious?


If you're concerned about the birdsmouth (which I've typically not seen done for something this size), you can put the top of the deep beam a little higher than the top plate and cut a smaller birdsmouth at the deep beam (and separate one at the top plate, if you want).


Quote:
Also, I'm not sure about a header not actually sitting on anything. Just nailing it in sideways really doesn't seem sufficient.
I wouldn't use nails there, at least not exclusively. You'll want a couple of construction screws at each stud. You can notch it into the studs, which eliminates shimming around the windows, but it's unnecessary. The allowable shear capacity of a #10 construction screw or a 10d nail is about 300 lbs. Drive 4 in at each stud, and you'll have 1200 lbs of resistance at each stud, more than enough to support the roof with several feet of snow on it.
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