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Small Cabin Forum / Member's Projects and Photos / 16x20 MN cabin questions
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jeepv8pwr
Member
# Posted: 4 Mar 2013 19:43
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I am in the process of buy supplies and materials for my cabin. I got everything for the walls so far, along with a stove and all chimney stuff. I will be building it on a slight slope that is mainly gravel and dirt below the top soil. It will have 10 ft. walls so I can have a good sized half loft. I have metal roofing already but no other materials.

What should I use for a foundation? I was thinking about using sonotubes but have heard bad results. Any ideas on the cheap. I know the frost line is at least 4 feet in MN.

What lumber and materials for the floor? 2x6 or 2x8? Green Treated or not? Full length 16' and 20' or 8' and 10' ? How much spacing? What kind of insulation?

What materials for roof? I dont know pitch or how to determine it, I want to use vault ceilings. such as the one I seen on here in Canada. Essentially the same cabin design. I want to have the materials ready for when the snow melts so I can start right away.

Thanks for any help.

oilersfan
# Posted: 5 Mar 2013 22:33
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The foundation will depend on the subsoil. If you have gravel then the soil isn't frost susceptible and you have little to worry about however if the gravel is mixed with clay/silt, you will likley want a foundation that reaches below the frost line. I am building in Canada (4ft frost depth) and I am going with 4ft deep pier foundations (sonotubes) as I have a clay subsoil. I will likely bell out the bottom of the piers to battle the upwards frost action.

I suggest for the rest of your questions start with a good framing book to flush out your pre design then come back to the forum with some more detailed questions. Spacing, sizing, etc. depend on lots of different factors. Do some reading and research. I bought a decent framing book at home depot and have figured most things out on my own.

Maple_Leaves
Member
# Posted: 6 Mar 2013 03:18
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Sounds exciting. You are farther along than me as I only have the land and am working on ideas for a cabin. 16x20 sounds like a perfect size. Im in MN too. Please continue to update as you continue on your project- your ideas sound great so far.

jeepv8pwr
Member
# Posted: 6 Mar 2013 12:47
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Oilersfan, thanks for the tip. I havent dug anyhole yet due to the frost still being in the ground, so I am not sure exactly what to expect as I dig down. My property has an old gravel pit not far from where i plan to build so I am assuming its the same type of material being on the same ridge. I think I will do the same as you and use sonotubes with those bell shaped bases they sell at Menards. I am basing my cabin on the one Mark built in Canada. Just trying to jump some research steps and figure out exactly what lumber I would need to frame it in like he did. Foundation and floor are whats keeping me from starting this project, bummer I didnt get it started before winter so I could be working on the interior now.
Why is gravel not succeptible to frost? Are you saying I could go out there right now (30 degrees) and dig my foundation holes?

Thanks a lot

jeepv8pwr
Member
# Posted: 6 Mar 2013 12:59
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Maple_ Leaves, It sounds like we are in the same boat. I just purchased 40 acres on the edge of the Superior National Forest last year. I first began of course by getting some deer stands built along with some wheeler trails and making a clearing for a build site. I have been staying in an RV but am sick of dealing with constant mouse problems, not to mention the cold weather and dealing with propane heaters and basically the crampt space. I found this site a few months back and have studied many of the projects. Originally I was going to go on a much bigger scale, until I seen the wonderful finished product that Mark built in Canada. I was quite surprised to see how nice and roomy a 16x20 can be especially with a half loft and 10 ft. walls. I already had steel roofing I got after an insurance claim from a tornado, being a part time worker and going to school the funds are quite low so I decided on doing the 16x20. So far I have spent about $1000 on lumber, insulation, and sheeting T111 for the walls. Also got a Performer wood stove, with all the recommended piping and metalbestos. cost about $850 should be enough to make the place a sauna at a 2200 sq. ft. rating !! I now just need to weather to cooperate so I can start digging and mixing concrete. I will post some pics as soon as I get some progress going.

jaransont3
Member
# Posted: 6 Mar 2013 13:26 - Edited by: jaransont3
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The main relocated part of our cabin is also 16x20. It is a good size and served the family we got from nicely for many years. We have added an 8x12 bedroom onto one corner. Our cabin is on the Iron Range in Northern MN in mostly sandy soil with good drainage. We put 4x6 pressure treated posts on the ground approximately 5 feet down. There are 3 rows of posts long the 16 foot dimension and 4 posts per row along the 20 foot dimension. We used beams made up of 3 2x8s sandwiched together to go on the posts. Maximum beam span is approx. 6.5 feet. The cabin floor joists are 2x8s (real 2x8s not modern 1-1/2 x 7-1/2) and they span the 8 feet between beams.

Been like that for 8 or so years with no issues.

oilersfan
# Posted: 6 Mar 2013 13:52
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For frost heaving you need water present between the ground surface and frost line...and freezing temps. Gravel is permeable meaning it doesn't hold water and thus no frost heaving. Sand is the same. Clay and silt are non permeable so they are considered frost succeptible soils. If you have a gravel subsoil you may want to investigate other foundation types.

You could dig your holes now but the cold temps would present other issues with placing concrete in less than ideal conditions.

jeepv8pwr
Member
# Posted: 7 Mar 2013 12:03
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I like the idea of using just green treated 4x4 or 6x6 for foundation but I am just thinking it wouldnt take much more to pour concrete if I had already dug the holes. To be honest I am not sure how good the drainage is, there is a creek and a lowland ash stand below the grade I plan on building on so Im sure wet season during run off there is plenty of water coming out of the old gravel pit as it holds water, lots of it. Worse before I dug a ditch in the hillside to allow it to drain. That old pit is about 10 feet below the level of where I plan to construct. Is building on solid concrete blocks or pavers out of the question? It seems like it would be hard to level things out being its on a considerable slope maybe a 8-10 degree.

Let me get this right. I should be using three sets of 3 20' 2x8 green treated for the floor beams with single 16' green treated 2x8s on the ends and 8' 2x8s in between the 20' 2x8s? Its not better to just use full length 16' 2x8s to span the whole thing? Is that too weak in the middle then? I just dont want to have too many joints. Thanks guys

VTweekender
Member
# Posted: 7 Mar 2013 12:36 - Edited by: VTweekender
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Quoting: jeepv8pwr
Let me get this right. I should be using three sets of 3 20' 2x8 green treated for the floor beams with single 16' green treated 2x8s on the ends and 8' 2x8s in between the 20' 2x8s? Its not better to just use full length 16' 2x8s to span the whole thing? Is that too weak in the middle then?

He has 3 beams the length, tripled up 2x8, 2 on outside and one in the middle...then put the floor joists between inside those beams with joist hangers I imagine.......you may be thinking he put the joists on top the beams.....so if you want to span the 16' with 1 lumber width then put the joists on top the beams, your joist span would be 8 ft with that middle beam there....

You won't need treated lumber for anything above 18" from grade.....so if your concrete tubes are up 18" or so then only need regular lumber for beams and joists..

jeepv8pwr
Member
# Posted: 7 Mar 2013 15:36 - Edited by: jeepv8pwr
Reply 


Is this what your talking about?

24" or 16" Floor support spacing?

3/4" 4x8 sheets of tongue and groove flooring sheets?

How about insulation and vapor barrier? Rodent proofing, like wire mesh screwed under beams?

thanks
floor.png
floor.png


VTweekender
Member
# Posted: 7 Mar 2013 18:36
Reply 


Yes thats it with your pic.....16" on centers is what you want with floor joists, otherwise could get bouncey......perfect with the 3/4 T&G plywood subfloor.......no vapor barrier needed .....insulation is really what type you prefer....and the mesh is a good idea...

jeepv8pwr
Member
# Posted: 18 Mar 2013 00:05
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I was told by a buddie who does construction to use three 2x8 beams in center of floor along with two 2x8 beams on outsides. Does that seem like overkill? Only thing left to buy is the lumber for the roof. Should I be using 2x8s or 2x6s for the roof? I already got 4 foot sonotubes, all the flooring tongue and groove, R19 for the floor insulation, floor beam brakets, so the only thing left is the materials to build the roof I already got 20 sheets of OSB for under the steel roofing. just need the rafter beams and what is needed to do the ones for a vault ceiling. Anyone got a materials list of what I would need? I was thinking 24 inch on center on a 20 foot length would be 10 beams on each side for 20 total without a overhang. So (20) 2x6x16 should do it? Am I correct of will this not be enough? Thanks again for any responses you input has surely helped me out.

VTweekender
Member
# Posted: 18 Mar 2013 16:42
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Quoting: jeepv8pwr
each side for 20 total without a overhang. So (20) 2x6x16 should do it?

You would need 11 rafters on each side for 24 on center......total 22.....you should use a ridge board as well.....either a 20 footer or two 10 foot .......if you go with 2x6 then use a 2x8 ridge board....if going 2x8 rafters then use 2x10 ridge board....

jeepv8pwr
Member
# Posted: 18 Mar 2013 17:00 - Edited by: jeepv8pwr
Reply 


OK, 22 thanks. would u use 2x6 or 2x8? Also what would the pitch be using 16 ft. beams? Would the 16 footers be sufficient to have enough room for my loft? Would that be a steep pitch? I am lost when it comes to pitch. I just figure that if I use 16 footers, I could use 10 sheets of OSB on each side of the roof.

VTweekender
Member
# Posted: 18 Mar 2013 19:02 - Edited by: VTweekender
Reply 


The wider the board the more insulation you can use, thats the decision for you...............16 ft. boards are going to give you a very steep pitch to that roof, you will be much more than a 12/12 pitch, which is steep to start with, a 12/12 pitch would allow a loft..........be very careful sheathing and putting the roofing on, its going to be hard and dangerous thats for sure........for a 12/12 pitch would be closer to 10 ft. boards....maybe 12 ft. with a cut...

jeepv8pwr
Member
# Posted: 18 Mar 2013 19:05
Reply 


Maybe 14 footers would be better. Do you know if there is a formula or something online to find out what pitch would be. thank VT

VTweekender
Member
# Posted: 18 Mar 2013 19:12 - Edited by: VTweekender
Reply 


Thinking more on it, 10 ft would be to short, more in the 12 ft board range.
Set your ridge board to the height you want in the middle, something like 7 feet from the top of your walls, bring the rafters up to that ridge board and cut the angle to meet the ridge board......then birdsmouth notch cuts to set on the walls...

You can see how a ridgeboard is set in pics here.. put 2x4 posts on top of the end walls under the ridge to get your height of the ridgeboard you want http://www.vermontcustomsheds.com/current_project ...if you don't want to get/buy a 20 ft. ridgeboard then use 8's, 10's or 12's of 1x8's and make a double beam 20 ft. ridgeboard with offset joints....to heavy if you use doubled 2x lumber, if you go this route..

ICC
# Posted: 18 Mar 2013 20:07
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12/12 pitch, 16 ft wide bldg, you need 14 ft rafter material to have any eve overhang at all 12 ft would just make it for rafters with no overhang if you cut very carefully grab paper, pencil, ruler and draw, graph paper works great makes it easy to count off squares for scale you'll learn more by drawing carefully on paper and using a drafting scale than by using any computer program, imo

if you draw a 45 degree angle that is 12/12 pitch, 12 inches horizontal for 12 inches vertical

jeepv8pwr
Member
# Posted: 18 Mar 2013 20:39
Reply 


Thank You, I think 14 footer sound good I want some overhang. Plus it will save on material costs.

knock
Member
# Posted: 19 Mar 2013 21:30
Reply 


I am also going to get started on a 16x20 this year.

I used this rafter calculator to help determine the lumber I will need and the cuts. (Don't recall if I saw this link on here or found it on my own.)

http://www.blocklayer.com/roof/raftereng.aspx

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