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Grizzlyman
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# Posted: 28 Mar 2025 07:35pm
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Snowload for Iowa is probably the 47 you mentioned. That’s ground snow. 33 would be the roof load which is 70% of 47. MN uses the same 70% formula.
Here’s MNs worksheet just as a sample.
https://www.dli.mn.gov/sites/default/files/pdf/bc_map_snowload.pdf
Not sure where 126lb/sf in a previous post came from… but that’s a LOT of snow lol.
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DRP
Member
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# Posted: 28 Mar 2025 08:56pm - Edited by: DRP
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Up around Donner's pass it's about 300 psf. You actually leave the codebook tables above 70 psf.
I can second the snow sticking to steep roofs. Clients up on Terry Peak in the Black Hills have had 3' of consolidated snow stuck on a 12/12 metal roof. It often seems to defy "common sense" but those are the days I need to build for.
The "always safe" cantilever follows the same principle I think we talked about on another thread. If the load can flow at a 45 degree angle or closer to vertical, there is no bending going on. Once you get out beyond that it needs to be designed "according to accepted engineering practice". The reference for that would be the NDS... and from there the referenced document is "Beam Equations" at awc.org under the publications tab and then turning to the equation labelled something like "beam overhanging support". You'll need to trace and sum the loads. I actually suspect you will pass but we do not assume. (I think you're fine with decent 2x8 or deeper. Curious why such a large canti.) We now have some numbers and the thing I suspect needs checking more is the 6x6 skid support spacing.
call it 14' wide with overhangs, assuming ridgeboard rather than ridgebeam load configuration. Half the load hits the rim on each side so 7' of tributary width x 47 lbs snow+ 10 psf dead load= 400 lbs per foot of roof load heading to the skid. The floor is light sleeping, call it 30 psf+ 10 psf DL x 6' of trib width=240plf
Add them up, 640 lbs per foot on the skids.
Umm, performing math, holler if interested, the 6x6's in #2 or better SYP can clear span no more than 5', so 4 supports per skid.
The cantilever passes in 2x8, do block between joists over the 6x6's.
A pic from yesterday, we got the floor trusses up today. Look at the chimney on the left wall where I had to remove a section to let the truss pass thru. I'll remove the rest above later when we have a floor to stand on. Anyway, one of the guys was sure it would collapse when I took that section out of it. At most it would have dropped away to about a 45 degree angle. As luck would have it I hit right on the inner liner joints so the flue liner is helping hold it all together as well. (the bath vents and 2 furnaces on different floors used that flue... so wrong!)
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PBC312
Member
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# Posted: 28 Mar 2025 10:34pm - Edited by: PBC312
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My cantilevers are a function of very limited space I can build this without having to pour concrete piers. Basically, I have one area of fairly flat ground where I can set skids about 9 feet apart without a lot of rigmarole due to the topography. I want a 12 foot wide cabin, thus the 18 inch cantilevers. I have 5 concret supports per skid, but they are 22 feet long. (16 foot cabin plus six foot porch.)
Today I was trying to get my 6x6 homemade skids level, and level to each other. It would be a lot easier if they were each dead straight! Alas, they are not. With each of them having some bow and twist, no matter how I much adjust and shim at each concrete block there’s so no way they will be exactly parallel and level. They are fairly close but not as good as I hoped. The way I’m thinking about it, what really matters is if the 12x16 frame I place on top of the skids is level and square. It would be easier to accomplish that if the skids were perfect but they aren’t. Does anyone have tips and tricks to get the frame level on somewhat crooked and bowed skids? I was thinking I would use composite shims and/or pieces of ashphalt shingles for small adjustments?. Any links to Youtube videos showing someone doing this? I haven’t started building the frame yet, maybe I’ll be surprised and it will be easy. If the weather holds this weekend I may start. If not, I’ll have to wait a couple of weeks before I get back to my property.
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spencerin
Member
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# Posted: 29 Mar 2025 08:19am
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Why not keep it simpler and have a shed builder build it for you and haul it in?
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PBC312
Member
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# Posted: 29 Mar 2025 08:33am
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And miss the fun?!
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PBC312
Member
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# Posted: 30 Mar 2025 12:52pm
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Update: The weather held yesterday. I got the skids level and my 12x16 frame built, all level and square. It went pretty smooth! Next step is to add blocking, then put in hardware cloth and XPS foam board in the joist bays. That will have to wait a couple of weeks when I’m back at my property.
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Grizzlyman
Member
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# Posted: 30 Mar 2025 01:40pm
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Nice. Any pics?
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PBC312
Member
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# Posted: 30 Mar 2025 06:37pm
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I’ll take pictures when I get back to the property in a couple of weeks.
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