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ctrapper
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# Posted: 7 Feb 2022 11:13am
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Hi there, I was wondering if anyone had thoughts on using a shed roof for a larger cabin (24x26). Based on the snow load (60) I am guessing you need some sort of LVL midway that would transfer the load down to a footing/pier. I get that using a conventional roof might make more sense, but we really like the modern look of the shed roof. We also do not want to use i-joists.
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travellerw
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# Posted: 7 Feb 2022 11:41am
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Quoting: ctrapper shed roof
Not familiar with that term "shed roof". Do you mean a Gambrel roof (like on a barn)?
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ctrapper
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# Posted: 7 Feb 2022 11:55am - Edited by: ctrapper
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Also referred to as a monopitch, skillion or lean-to roof.
https://www.thespruce.com/thmb/9UZAK0PhPLB2soyDgqekwEgSIXU=/1500x844/smart/filters:no _upscale()/SpruceShedFGYArch-5bafda7946e0fb0026b0764f.jpg
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gcrank1
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# Posted: 7 Feb 2022 12:25pm
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I had considered that 'sorta', but split it down the middle (a 'split level roof?). The 'front roof' was then lower at the top so I could have a row of light and ventilating windows.
Def a more 'modern look' than a conventional peaked roof and solved the peak venting issue if you have high ceilings.
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rpe
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# Posted: 7 Feb 2022 12:29pm
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It would be an interesting design for sure. Could an interior wall be used to support the mid-span beam? 2-piece rafters, sitting on that beam? I'm looking forward to what the experts advise on this one!
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ctrapper
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# Posted: 7 Feb 2022 12:31pm
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Yes, there will be an interior wall that splits the space....
gcrank1, that is a neat thought, do you have any pictures of what that looks like?
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rpe
Member
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# Posted: 7 Feb 2022 12:37pm
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Maybe like this, but with enclosed space rather than porch?
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ctrapper
Member
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# Posted: 7 Feb 2022 12:43pm
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Yeah, looking more at something like this....
https://i.pinimg.com/originals/14/13/94/14139423931bf4d153f7e92769346752.jpg
Its just that with a 24x24 cabin, I'd think it will need some serious engineering with a 60psf snow load.
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rpe
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# Posted: 7 Feb 2022 01:07pm
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The pic was in response to gcrank1's mention of the split level.
There is a cottage similar to what you just posted on our lake, manufactured of Structural Insulated Panels. I've been inside it, and there are two structural interior walls that split the main space into bedroom/bathrooms on either side, and a large common area/kitchen in the middle. The supporting walls run parallel to the rafters, and support I believe two cross-beams that act to reduce rafter span to roughly 1/3 original. Now the term 'rafter' isn't really applicable here, as I believe the roof is also engineering SIP panels in this case. I could probably get some pics if interested.
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ctrapper
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# Posted: 7 Feb 2022 02:12pm
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That sounds like what I was thinking. I was thinking of doing a roof system that is a metal roof + OSB +2-4" of rigid foam + pine planking over 2x12 rafters. The idea is to stain the underside of the planking a darker color, and paint the 2x12s black for a modern look
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rpe
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# Posted: 7 Feb 2022 02:45pm
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I had that fellow send me a couple pics. The front has four sliding patio doors, with fixed windows above each. The two middle patio doors enter the common area. The outer two enter the associated bedrooms. From the looks of the interior picture (viewing from side entrance, through common area to far side) there is a beam that supports roughly mid-span.
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gcrank1
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# Posted: 7 Feb 2022 03:13pm
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Yes, rpe, you got what I was thinking.
When I considered the necessary height/headroom needed on the back wall, the roof run to the front over a wide distance and an adequate pitch it made the front too high and blocky for our tastes.
It is fairly easy to do a cardboard box, sorta to scale mock-up to get a sense of it all if you are a visual kind of person (plus it is kinda fun).
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rpe
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# Posted: 7 Feb 2022 03:39pm
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Quoting: gcrank1 When I considered the necessary height/headroom needed on the back wall, the roof run to the front over a wide distance and an adequate pitch it made the front too high and blocky for our tastes.
Yeah, I was wondering about that. It works out fine for a 5 ft porch, but could get awkward at much higher dimensions.
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ICC
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# Posted: 7 Feb 2022 04:19pm
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It's a split shed roof. With windows a gcrank1 described, the windows are known as clerestory windows. Link to search found images.
A load-bearing wall or beam, with a proper load path to the foundation, is required in the area under the split. If awning windows are used for the clerestory windows and a method of operating from down below is provided they can be very useful for ventilation in hot weather.
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ctrapper
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# Posted: 7 Feb 2022 04:32pm
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Yeah, definitely solves the roof span/load issue. Just not wild on the look of it. I think I would rather have the single pitch roof with internal structural components to make it work. Maybe I'll even look at timber frame?
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NorthRick
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# Posted: 7 Feb 2022 04:50pm - Edited by: NorthRick
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I built a 24' x 24' "pavilion" with a shed roof. It has beams on either end and one in the middle (made from 2x lumber not an LVL) which is supported by a post in the center of the pavilion.
It basically has 12 ft rafters running from each end to the middle beam to support the roof. It's in McCarthy, Alaska, so it sees some snow and has been there about 10 years now.
No insulation and not prettied up in any way. Keeps the rain off us when we are out there, which is its purpose.
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ctrapper
Member
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# Posted: 7 Feb 2022 04:53pm
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Yeah, I think if you are cutting the span to 12' you have a lot of options, even with snow load.
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Aklogcabin
Member
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# Posted: 9 Feb 2022 10:17am
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On my 20 x 24 garage I used 16" engineered TJIs. They can span 20' and have the required minimum dead load weight. Really nice for insulation as r- 38 fits n leaves a couple inches gap above for air ventilation.
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Nate R
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# Posted: 9 Feb 2022 01:15pm - Edited by: Nate R
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I looked at this too, but got away from it for similar reasons to others...roofs at decent slope in this kind of size get to some weird proportions
OK, no i joists.... what about LVLs AS the rafters?
Otherwise might look at MSR lumber. 2x12s 12" oc with a 2.0E (2400 MSR) will span 23'7" at L/240 for a 60 PSF snow and 20 lb DL.
-Nate
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ctrapper
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# Posted: 9 Feb 2022 05:32pm
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I am thinking that we can make it work with some support member 1/2 way or so. That would limit the span to 12-13 feet. Going to have an architect we used on our house take a look...
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Brettny
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# Posted: 10 Feb 2022 10:18am
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An architect is not an engineer. You need an engineer for this.
Yes running a beam down the middle of the span will help but you may also need to support the center of that beam. This could be a wall or a post and will need a footing.
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ctrapper
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# Posted: 10 Feb 2022 10:23am
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For sure. He has an engineer he uses for these things. The center wall dividing BR from living area should work, hopefully they can figure it out. Or, he may end up convincing us to do something completely different  . We realized a long time ago that using a proper architect to design something if you not using an off the shelf plan is well worth the expense.
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Brettny
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# Posted: 10 Feb 2022 12:55pm - Edited by: Brettny
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If your doing a dividing wall down the whole center than no beam is needed. The wall becomes the load supporting member. If you only want a wall down half of it your then left only needing a 13' beam and possibly doable with no LVL.
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