Small Cabin

# Posted: 7 Apr 2011 12:29am - Edited by: MtnDon
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designing the rafter sizes gets complicated by the cross tie that is set above the side wall height. That introduces forces into the rafters that normal rafter calculators and tables do not take into account. It's an engineers territory.

There also may be some unexpected side (outward and horizontal) forces generated by the rafters on the tops of those side walls. They should be controlled by the 8 ft high crosstie, but I'd want that checked. A-frames usually have the lower end of the rafters securely connected to a strong anchor.

The left hand sketch and center drawing don't jibe with the wall/roof detail, to my eye.

Just
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# Posted: 7 Apr 2011 09:21am
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Im no engineer, but if i were you I would extend the pony walls 10 in. then build some roof truses with 2x8 bottom cord for your upstairs floor .then set them squarly on the outside walls.. i think you could still get the a-fram look you want by extending your rafter tails abit !!you would only have 6x10 ceilings but i have found them to be adiquit for a cabin !!

# Posted: 7 Apr 2011 09:54am
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Jeremy165
Welcome fellow PNWerner!

Quoting: MtnDon

There also may be some unexpected side (outward and horizontal) forces generated by the rafters on the tops of those side walls.

Can't go wrong with MTD's advice. I'd be considering a collar tie in regard to the size of cabin you are building.
I'd like to comment more, since your construction is very much like ours, but since I'm at work..........
Here's some pix of the build of our tiny (10x12) cabin.

walls.JPG

framing_it_up.JPG

ready_for_doors.JPG

Cozy_cabin.JPG

# Posted: 7 Apr 2011 10:19am
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Think about how much insulation you might want in the roof. That pretty much dictates the use of 2x12 rafters to get an appreciable amount. Plenty strong; plenty heavy too.

Just
Member

# Posted: 7 Apr 2011 10:45am
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as usual don is rite 2x12 rafters should be strong enough!!and still use your 6 ft .side walls,I however would still consider lowering your ceiling height to 7 ft.

# Posted: 7 Apr 2011 11:16am
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Insulation?
2 x 12?
It's a 12 x 16 cabin (shed), right?
With an extreme pitch, right?
Get too tight, and yer stove will run you out.
........and 12" is overkill, right Don?
I like seeing the planks from inside...like a true cabin..... but not 12" wide ones, and covering insulation would dictate more wood, like T&G, or (God forbid) something like OSB......

My opine

# Posted: 7 Apr 2011 11:26am
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Where I am the interior of small spaces get hot very quickly spring through fall when there is no insulation at all. So I never imagine that anyone else might build without any insulation. Maybe that's my error. And in winter, well it is too small a space for a wood burner, and all other forms of heat cost $, so again I think in terms of insulating. Maybe 2x12 would be overkill for this size, but I'd still want some insulation, but that is simply me.

# Posted: 7 Apr 2011 11:36am
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Quoting: MtnDon

Maybe 2x12 would be overkill for this size, but I'd still want some insulation, but that is simply me.

Yeah, it's dependant on a lot of considerations.
Love your educated opines Don

Just
Member

# Posted: 7 Apr 2011 11:56am
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jer is a skier sounds like winter use !!

# Posted: 7 Apr 2011 12:47pm
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Thanks to all your replies. It gives me more to think about!

I'm not worried about the size of my members from an insulation point of view. I'm worried for structural, what size members would I need for it to be solid?

Gary, Yes I'm going for a look really similar to yours. I read through your cabin thread and it looks like you used 4x4s for your trusses. Something like a 2x8 or 10 would be comparable to that?

Sounds like no one really thinks my plan will work due to the outward horizontal forces. How is my plan that different from Gary O's?

Now if I think about Just's comment I see his point. If I had framed my pony walls at say 8ft high, my A-frames would sit right on the wall's top plate and really lock it in. But I have 6 ft walls, I'd rather not rebuild those, any ideas on if my 6ft pony walls will work with my plan?

So I still have 3 main questions:
1 - Lumber size of my A-frames, size of the floorjoist/crossbeam and size of the roof rafters.
2 - Is 24 in 12 too steep? I don't want it to look like the picture I attached below.
3 - Are 4' overhangs too big for rafter tails?

Thanks,
Jeremy

steep.jpg

# Posted: 7 Apr 2011 02:05pm - Edited by: Gary O
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Quoting: Jeremy165

Sounds like no one really thinks my plan will work due to the outward horizontal forces. How is my plan that different from Gary O's?

Yeah, I don't know of any ready calculations in regard to a roof pitch like ours.
I applied some seemingly common sense, however, since there is not as much pressure or stress due to the pitch.
The MtnDons of the world have the surest/safest of advice, outside of architectural/engineering calculations.

Quoting: Jeremy165

But I have 6 ft walls, I'd rather not rebuild those, any ideas on if my 6ft pony walls will work with my plan?

That's the reason I went with 4x throughout...I lag bolted everything.......

# Posted: 7 Apr 2011 03:11pm
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1. (a) 2x6 will pass for rafter size if insulation is of no concern. You did not specify species, grade or spacing so I used the worst of the commonly available grade #2 lumber. It seems to work at 24 or 16" spacing.
(b) 2x6 would make it to 9 feet width using typical attic/sleep space loading with 24" OC; 10 feet with 16" OC. 2x8 would provide for greater widths. You have to draw and calculate the length required at the 8 ft. floor to joist height. I would not place those joists any higher than 2 feet above the wall.

3. since there's not going to be any snow sitting on those tails their length is no issue.

Because those rafters are going to be very long, and there will be more roof sheathing and roofing than the typical lower pitch roof there will be greater weight bearing on the walls. What is the stud spacing of the walls you have built? It would be best to position the rafters directly over the wall studs because of the higher than normal loads.

A big concern may be what a high wind will do on those sails you will have for a roof. I don't know how the walls are anchored to the floor and the floor to the beams and the beams to the piers and the piers to/in the ground. Side load by wind is probably the biggest concern. At that pitch not much air will spill easily over the peak as it would in a lower 6/12 pitch. FYI, a lower pitch has other problems with wind; lower pitches act like wings and create lift.

# Posted: 7 Apr 2011 03:35pm - Edited by: Gary O
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Quoting: MtnDon

there will be greater weight bearing on the walls. What is the stud spacing of the walls you have built? It would be best to position the rafters directly over the wall studs because of the higher than normal loads.

Absolutely
That's where the majority of the load is.

Quoting: MtnDon

A big concern may be what a high wind will do on those sails you will have for a roof.

It's a concern, but not as much as the lift probs mentioned for more conventional pitches.
'Sails'...funny

6" members sounds right, but I'd use 4 x 6, for aesthetics and structure forgiveness............

soundandfurycabin
Member

# Posted: 7 Apr 2011 04:54pm
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For the roof pitch, I'd find some triangular windows first and build the roof to match. To my eye, it would look goofy if the roof and windows were at different angles.

# Posted: 7 Apr 2011 08:02pm
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Quoting: Jeremy165

2 - Is 24 in 12 too steep? I don't want it to look like the picture I attached below.

24/12 would probably look like the picture....or worse
It's funny, but not a suprise, that a cursury web search only shows up to 12/12 (45°) pitches.
So I googled 'A' frame roof pitch and it appears my 58° pitch is somewhere around 15/12

Hope this helps you Jer

Just
Member

# Posted: 7 Apr 2011 08:49pm
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that meens a 2x6 x 12 would make 1 rafter , there would not be much head room in the loft.. it's nice to be able to stand up to get dressed.. you would have to stand between the rafter tyes!

# Posted: 7 Apr 2011 09:46pm
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Quoting: Gary O

Quoting: MtnDon
there will be greater weight bearing on the walls. What is the stud spacing of the walls you have built? It would be best to position the rafters directly over the wall studs because of the higher than normal loads.

Absolutely
That's where the majority of the load is.

I mentioned that only because in a normal, less heavy roof design, it does not matter, as long as two top wall plates are used. If a single top plate is used then it does matter. Makes it easy to use 24" OC wall studs and 16" OC rafters; or vice versa.

Just
Member

# Posted: 8 Apr 2011 08:43am
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you can make simple windows like these .I use white pine for the frames and p.t. for the sill. they will need to open in the loft as it gets realy hot up there !!

100_1356.jpg

# Posted: 8 Apr 2011 12:46pm
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The 2x6 Pony walls are 16" oc. I was thinking the A-frames would be 16" oc and land on the the studs even though I'm doing double top plate.

I think that picture I attached in my last post is way steeper than 24 in 12. More like 36+ in 12. I like Gary O's cabin at 58* or about 15:12. When this area gets the occasional 4 feet of snows I want to know the roof sheds it if I can't make it up there.

I'm thinking about rebuilding those pony walls up to 8ft and having the loftjoists of the A-frames sit right on top of my walls top plate. It would only cost about $100 of 2x6 studs and I'm sure I'd reuse the lumber from my original walls somewhere. Seems like the thing would be way more solid.

I'm not worried about winds. It is a heaily treed area and its doesnt get windy at all. Regardless, I have a poured concrete footing w rebar to my sonotubes which has a set-in-concrete post base/simpson tie to my beam with simpson ties to my joists, plywood is glued and screwed, pony walls will be bolted down. Its not going anywhere.

Now flooding could be a more likely issue. Its in a 100 year flood plain. Supposedly I could see 5 feet of water. Luckily thats at the height of only my floor joists. It is one reason I'm trying to keep total project cost + land at about 11k. But I've talked to my neighbors who have been in the area for a couple generations and I don't think I'll ever see it happen. I'm sure others have said statements like this before though...

There will be ample headroom in the loft and windows that open to let out the hot air in the summer. It will be over 8 feet high in the loft at the peak and its still 4 feet tall a width of 6 feet, so thats roomy enough for me and my lady.

I'm thinking about making some of my own fixed windows so I can have some large triangles on the front. I don't know if I have the ability or patience to make hinged windows that open.

So I guess the consensus is my A-frames should be composed of 2x6 rafters with possibly 2x8 floorjoist/crossbeam to span 10 feet, all this is 16"oc. This will be sitting directly on top of my newly rebuilt 8ft tall 2x6, 16"oc pony walls.

Wow, I feel so much more confident of my plan. Well, this part of the plan at least.

I'm trying to head up Sunday, I'll take some photos of the progress and post them here. Thanks all!

Jeremy

# Posted: 8 Apr 2011 04:13pm
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Quoting: Jeremy165

I'm thinking about making some of my own fixed windows so I can have some large triangles on the front. I don't know if I have the ability or patience to make hinged windows that open.

Yeah, hinged triangles w/be a trick
I'd do something as drawn, with an opening window in the center

PEAK_WINDOWS.JPG

# Posted: 9 Apr 2011 12:00pm
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Yeah thats a cool window layout for the loft area.

I attached another cool one I like - look at all them windows! But my cabin is only for occasional use and I think all those windows makes for a security issue.

I've settled on a pitch of 20 or 21 in 12. A 60 degree triangle has a pitch somewhere in there and I like the proportions of that triangle.

I really like the finished look of the cabin in my final pic. I will finish in a similar manner. First I gotta get a roof on the thing though! Cheers

Jeremy

all_windows.jpg

plans_pic.jpg

# Posted: 9 Apr 2011 12:34pm - Edited by: Gary O
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Yeah, a good overhang is essential in snow country.
With a roof like yours, it's pretty much an extention as pictured. Otherwise things get a bit cobbled looking.

Keep that snow board under your feet, and keep us posted (with pix!)

Gary O'

# Posted: 23 Apr 2011 03:40pm - Edited by: Jeremy165
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I've been out to my cabin a few times since I last updated you.

So here are 2 out of the 3 bridges you have to cross to get to my place. Because of the shoddiness of the bridges, I had the 4 ton of 2" crushed rock I need dropped on the far side of the bridge from where I want it. I spent all day shoveling rock into buckets, pouring buckets into 3 garbage cans in my van, then driving across and pouring and spreading. I'm only 27 and man did I have a sore back. No offense, but I can't imagine how some of you more experienced fellas feel after a day at the cabin.

Here are a couple pictures of the bridges and the driveway before picture. I cleared the driveway of all fallen timber and brush last November.

I went back yesterday. My first sunny day I've had I think since I purchased the property. Theres a pic of the driveway after I spread all that rock. I used a lot to fill some potholes on the approach also.

So last November I built the floor and layed ¾" plywood and built my pony walls and was all gung ho and got stopped by the snow. I laid the walls down, threw tarps over everything and hoped for the best.

I finally pulled the tarps yesterday and all of my 2x6 untreated studs looked like crap. Not warped but they sure had mold. I decided these walls will make a nice wood shed and threw this together. Is the mold harmful to my firewood? With all the air flow and in some sun, is the mold going to stop growing and just look discolored.

Here's the cabin structure and floor. 4x10 beams, 2x12 treated joists, ¾ T&G plywood.

I bought some more 2x6 today and will precut them in my garage. I took your advice and got 8footers, so now my loft joists will sit right on top of the wall framing. I was thinking about it and this is going to be waaaaaaaay easier to put up my roof rafters. Instead of trying to tilt up these massive A-frames. I am going to install my loft joists on top of the walls, lay plywood down, then build my roof rafters with gusset plate on the loft platform and tilt them up. Then I will bolt the rafters to my loft joists and those will by the crosstie for the A-frames. I can likely do this 1man without dragging the girlfriend or my lazy buddies out.

My big question is – Is my plywood subfloor ok? From the top it looks fine but the underside doesn't look as nice. Is this bad mold? Is there too much of it? I really don't want to scrap this plywood as it took some time to install it and I don't want to replace it. Can I get away with spraying and scrubbing with that mold/mildew spray or should I ditch it. I don't want to risk infecting the whole cabin.

FYI – For the underside I planned on caulking all plywood to joists, then installing rigid insulation to all the bays and then vented soffits or similar to the bottom of joists.

Last pictures are everyone's favorite – the outhouse! My property is roughly a rectangle. Just off the back off my property, is an outhouse for the adjacent property. I asked one of the few year-round residents about the property and he says no one has been there in 30 years. I decided to clean up the outhouse a bit and use it as my own. All I've done so far is put a new toilet seat and lid on. But I really enjoy the facilities out here.

That's all for now. I might head out Sunday morning. Cheers.

JB

Suspension bridge

Boxcar bridge

Driveway cleared

Driveway w gravel

# Posted: 23 Apr 2011 03:44pm
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The rest of the pictures:

Here are those mold pictures. How bad is this? Should I ditch all the plywood and bring out new sheets?

crap studs become wood shed

Cabin

undercabin - moldy

moldy plywood subfloor