Author Topic: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota  (Read 1942 times)

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Offline Strix

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16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« on: April 07, 2017, 12:45:03 PM »
Hey All,

Winter is finally over for us in MN, and I am about to start the excavation process for a cabin I've been planning for some time now.

Current plan is to dig a full basement to get around the frost depth we have in MN. Code specifies 5ft minimum depth below grade, so that's how far down this thing will go.
Foundation will be full perimeter CMU with filled cores and a 24" x 9" footing profile. Waterproofing membrane to be installed around the lower 78" of the foundation before backfilling.

I have some sketchup designs here if anyone wants to take a stab at issues with it. (first floor doors/windows aren't in the model yet)
First floor sitting on 11 7/8" I-joists to span 14' 8" across CMU walls. 24" O.C.   3/4" OSB sub-flooring
Long-axis walls are balloon framed 2x6, 24" O.C. with 12' tall studs and a floor starting at 8' height. supported additionally by 8" ledger and fire blocking at 8'.
Short-axis first story walls are standard 8" height with double top plate. also 2x6 24" O.C.

1/2 story and roof are where things are a little more interesting... Roof has structural ridge, 3-ply of 26' 1.75x16" LVL. Big mother of a built-up beam. Allows for a clear 23' open span in the room.
Ground snow load here is 60psf, roof pitch is 12/12. Rafters are 2x8 24" OC. Will be secured with metal hangers and hurricane straps. I have no idea if I can get away with the slider windows right down the center of the beam's path to the foundation. Another option is two smaller single hung windows side by side of the supporting column as it goes down to the floor. Less header headache. I am still worried about the floor being the rafter tie 3 feet below the point at which the roof exerts some thrust on the wall... With the ridge holding half the weight, each stud is still going to see ~90lbs of thrust outward. Seems manageable for each 2x6 stud, but I haven't calculated beyond this...

The floor is to be 2x12 or I-joists again, except in the center portion where half the floor is open to let in light from (potentially) skylights and let heat up from a wood stove. I think this floored portion in the center may need some better engineering to deal with wall thrusts. Not sure on this.

Collar ties are just to hang electrical and what have you. I like having the void in between each pair as it seems ideal to tuck away wires and such!

Soil is sandy clay, but with the total weight of this building on the total foundation footprint I've prescribed, the soil will be fine. 156 sqft of footprint and total snow-loaded house weight of 80,000lbs

Here's some sketchup stills of the frame I'm imagining... (sans basement) Open to any suggestions on this. Really would like to have plans in a "do in once, do it right" state by mid-summer or so.
Thanks for stopping by!














Offline ChugiakTinkerer

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #1 on: April 07, 2017, 03:03:05 PM »
My knowledge is fairly limited, pretty much what I've gleaned from this forum.  So likely I have questions but no answers.  ???

First off, are you dealing with a permit authority?  Your sketch looks to be IRC compliant in many ways, which is great.  But the county inspector or equivalent will be the final authority, if apropos.

Having a structural ridge means you don't have to worry about any outward thrust.  Your ridge beam will push back against the rafters resulting in no thrust.  So your knee walls are good.

I also don't know if you can get away with having a single slider window centered on the gable wall.  It certainly would be more straightforward to extend the king and jack studs straight down from the ridge beam to the sill.  I'd look at some beam calculations and see what your header can accommodate.  That end of the beam will be supporting 1/4 of the roof load.  Doing a quick check using ground snow load, it looks like a 60" header made of two 2x12 will fail  (see http://www.timbertoolbox.com/Calcs/beamclc_ctrptld.htm ).   However there are many factors including roof pitch and type of roofing material that would reduce the roof snow load.  I think a triple 2x12 of #2 doug fir will be strong enough, but the calcs are close enough that I'd recommend checking with a professional on that.  If it's a 54" window you're probably good to go with a triple 2x12.

The only thing I feel comfortable saying you need are some support studs on the ground floor gable wall directly under the window header ends.  Of course it could just be its because your sketch is still a work in progress.  You want to be able to trace vertical support for the roof from the ridge to the footer, and you need a few jack studs for additional support.  You would also want to have load-bearing blocking in the loft joists to facilitate the stress down to the first floor supports.
My cabin build thread: Alaskan remote 16x28 1.5 story

Offline NathanS

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #2 on: April 07, 2017, 03:13:04 PM »
Looks like you are on the right track to me!

Those LVLs will probably come in at 300-400 lbs each, have a plan for getting those puppies up there.

Wouldn't cost much to step those 2x8 rafters up to 2x10 or even 2x12 to have a much stronger roof. What is your plan for insulation and ventilation as well? With 2x8 I think it would have to be a bunch of foam on the sheathing and then furred out to prevent ice damming. Current IRC code is going to want you at at least R-49.

Another possibility for the windows under the ridge would be to use a tripled up LVL - you could order your ridge a little long. Would still have calculate everything out to make sure it works.

Offline HappyOne

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #3 on: April 08, 2017, 05:25:27 AM »
Me no can helpy Strix but excited to watch your build progress. East Central huh? I bought some land north and west of Pine City recently so maybe we in same general area.
Looking forward to what you do - good luck on all ;)

Offline Strix

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #4 on: April 08, 2017, 07:54:35 AM »
First off, are you dealing with a permit authority?  Your sketch looks to be IRC compliant in many ways, which is great.  But the county inspector or equivalent will be the final authority, if apropos.
...
I also don't know if you can get away with having a single slider window centered on the gable wall.  It certainly would be more straightforward to extend the king and jack studs straight down from the ridge beam to the sill.  I'd look at some beam calculations and see what your header can accommodate.  That end of the beam will be supporting 1/4 of the roof load.  Doing a quick check using ground snow load, it looks like a 60" header made of two 2x12 will fail  (see http://www.timbertoolbox.com/Calcs/beamclc_ctrptld.htm ).   However there are many factors including roof pitch and type of roofing material that would reduce the roof snow load.  I think a triple 2x12 of #2 doug fir will be strong enough, but the calcs are close enough that I'd recommend checking with a professional on that.  If it's a 54" window you're probably good to go with a triple 2x12.

Right, I knew I was forgetting some important first post information here...

I am not dealing with code in this build location, but would like to build what I can to code if I can. At this point, I fully intend to just have this cabin in the family for a long time, but it is absurd to think I'd never need to sell it...

Regarding the windows... I think it probably is just easiest then to not try to break the line from the ridge to the foundation. I'll spec out some skinny single or double hung windows to place outside the support column running down. This would also extend to the first floor wall; I'd split the wall with a center support column and avoid having double or tripled-up studs elsewhere in the wall due to the header above. "Keep it simple, stupid", right?  d*

Offline Strix

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #5 on: April 08, 2017, 08:13:13 AM »
Looks like you are on the right track to me!

Those LVLs will probably come in at 300-400 lbs each, have a plan for getting those puppies up there.

Wouldn't cost much to step those 2x8 rafters up to 2x10 or even 2x12 to have a much stronger roof. What is your plan for insulation and ventilation as well? With 2x8 I think it would have to be a bunch of foam on the sheathing and then furred out to prevent ice damming. Current IRC code is going to want you at at least R-49.

Another possibility for the windows under the ridge would be to use a tripled up LVL - you could order your ridge a little long. Would still have calculate everything out to make sure it works.

Whew! Glad to hear it...
Yeah, I've recently made the design change to the single continuous-beam LVL's, which open everything up but are heavy. Current plan is to borrow a friends scissor lift and get them up. It's going to be a challenge to move that thing around even before I have to lift it...

Thanks for suggesting the stronger roof rafters, hadn't actually considered it being a small price jump. Due to the snow, it would be great to have the roof as strong as I can get it. And i can get away with the 2x8, but probably should go higher if not just for insulation purposes. Current plan was to vent the rafters through the standard soffit approach and use those XPS vent panels along with fiberglass to fill the remaining cavity space. Along with a ridge vent or gable-end vent. More to come on this. Currently have no actual livable space on this plot of land, so the ulterior motive here is to get something (anything) dried in so I can overnight without being in my car... Doesn't need to be warm right away, just not wet and open to the mosquitoes...


Offline akwoodchuck

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #6 on: April 08, 2017, 09:18:06 AM »
Looks nice...only thing that jumps out at me is I would block in between the rafters at the birdsmouths, and block out the barge rafter for strength and soffit nailing....

Offline Oakwood

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #7 on: April 11, 2017, 04:33:22 PM »
Did you consider manufactured scissor trusses such as these on a 16x24? This provides 12" for insulation. Total cost delivered and placed: under $2000.


http://s682.photobucket.com/user/tonydolk/story


Offline ChugiakTinkerer

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #8 on: April 12, 2017, 09:22:53 AM »
...
Currently have no actual livable space on this plot of land, so the ulterior motive here is to get something (anything) dried in so I can overnight without being in my car... Doesn't need to be warm right away, just not wet and open to the mosquitoes...

I hear ya!  I opted for the incremental approach and am slowly working my way up the habitable structure food chain.  My first is a temporary shelter, a "Weatherport by Hanson" Quonset hut that I erected on a 12x20 platform.  Here it is behind my snowmobile and lumber pile:



Once the cabin is built it will become my storage shed.  For now it serves as the warehouse, mess hall, and bunkhouse.  The weatherport was an incredible deal on Craigslist.  There might be something in your area that could serve the same purpose.
My cabin build thread: Alaskan remote 16x28 1.5 story

Offline Strix

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #9 on: June 28, 2017, 06:28:22 PM »
Hey all,

Been quiet here lately, but there have been some milestones met in the build process. Lots of pictures, bear with me...

Permitting was required to start the build, so there were some hoops to jump through. Luckily, there is no code requirements... the permitting is mainly for zoning purposes and they simply verify the building is built where you submitted the paperwork for. $25 fee, and I'm set to dig "legally". (Though I had started digging anyways...)

Dimensions of the cabin are now a little wonky as I've decided to go with a dry-stack approach with the foundation walls. I've added extra block to each course of the foundation wall to account for the lost 3/8" per block to get back close to the original 16 x 24 dimensions. Hopefully won't need to change too much else with the extra inches here and there.

Had the muddy driveway re-graveled last week, and what a difference it makes... Been making the commute to the property in a little Civic, which had a hard time in the mud. No more! It's dry and compacted now, makes me a happy camper.  ;D



Concrete block delivery happened yesterday. Got a pretty good deal on the block from a guy who bought out a bankrupt masonry company... 80 cents a block. And one third of them are plain-ended! Great for me now that I'm not using mortar... Would have needed more stretchers if using mortar, but this worked out great. Considering the guy I bought em from was awful at communicating back, I figured I was getting all stretchers. Whoop. Bonus cool dark grey color too.





Cleaning up the demolished old house is almost complete. I've found a lot of buried garbage which the previous owners left there when hunting. Apparently in the 90's? Lots of surge cans and old cherry coke... Funny.

Picked up insulation for the foundation from some fellas doing a flat roof replacement on a warehouse. 3" thick! Cruising craigslist for materials really helps keep costs down if you have the time to do it... Keeping them in my barn, which is literally one strong wind away from tipping over... It's braced all over with wood, no idea how long we can keep the thing up.



Bought all the rebar for the concrete work and carried it up in my civic... She didn't like that very much but no damage done. Ha. Seller was nice enough to cut them to length for me so they weren't dragging on the highway. Could have kept them longer if I had a means to get them otherwise, but I'm not building a rocket ship here. It'll do once it's in the basement slab.



Planning to get the hole ready for the footing pour, hoping to have that done by the 3rd week of July. It's slow going by myself, so I really should invest in some beers and kidnap a crew of friends for a weekend... Would go a lot faster! Still learning as I go. Every day I work I get something done and that alone is enough!

-S





Offline Strix

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Re: 16 X 24 1&1/2 Story Cabin in East-Central Minnesota
« Reply #10 on: June 28, 2017, 06:32:16 PM »
Here's a before shot of the driveway for anyone interested... It was absolutely a no-go for me in my car. Needed 4WD, or else just give up now... turns out in winter it also doesn't work since it's all ice down there. Recently bought a Chevy Silverado to use up here, so I'm almost sad it won't be conquering that mudhole once I bring it up...