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Birch
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# Posted: 11 Sep 2018 06:59pm
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Hi folks,
I am building a small "cabin" -its my second one -first was 14x16. This one I'd like to make 20x24 and I have some questions I hope you might all have thoughts about. 
If I build stick style, 20x24 with a half loft, and want the ceilings on first floor to be 9' and upstairs have 4' knee walls what do I need for ceiling support and wall support?
Do I need to use rafters or trusses, or can I get away with an open structure on the half of the room without the loft? I have seen this elsewhere and don't know how they do it. Any thoughts?
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snobdds
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# Posted: 12 Sep 2018 12:24am - Edited by: snobdds
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I built that cabin you want. It was not easy to design or build. I wanted two things, eight foot ceilings on both the main floor and loft and the roof had to have some pitch to shed snow. An architect had to design it, I didn't realize how complex my request was. It requires 12 foot walls and a complex rafter roof. Under enclosed roof space its 20x24, but with the side deck its 20x30. That's the minimum size to make the requirements and angles work.
I have a lot more picture's that I need to update my build thread
on, but this will give you an idea.
http://www.small-cabin.com/forum/6_7785_0.html#msg111554
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Birch
Member
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# Posted: 12 Sep 2018 08:11am
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Snobdds, thank you for the reply- I appreciate your thoughts and the photo link - your place is great!
I see a lot of designs/photos of log home kits with a half loft and an open ceiling format over the rest of the room.(No rafters cutting across and blocking the view) I am wanting to make a stick style rendition of this but I am not finding plans for this. Any leads?
Snobdds- Do you have any photos of the interior and the roof supports and structure before the exterior roof got put on? it sounds like you needed complex designs made - and it may be beyond my building skills, but I'd like to see what was needed to accommodate for the open space.
The cabin I built over these last few years is 16'x14' and a great little space with a half loft. I have been living in it and it is pretty small. I want to use it as my studio as it was originally planned and build a bigger version to live in - thus designing a 20'x24' space. The front wall will be south facing and mostly windows. I want an open feeling and would like to find a way to do without the rafters stringing across the living space.
I'm in rural Maine, good snow fall- so I plan on an 11/12 or 12/12 pitch and metal roof. I'm still at the planning stage but hope to break ground next week and get the footings and floor platform in this fall and build the rest next spring/summer.
Want to say, I've been loving reading this site and just joined as a member as my project is underway and I'd love feedback. Thanks.
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ICC
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# Posted: 12 Sep 2018 10:44am
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Technically speaking, you can not do a wide open, cathedral like ceiling space without using engineered trusses. When a regular flat ceiling is designed correctly the ceiling joists sit on the top plates of the side walls and are fastened to both the top wall plates and the tails of the rafters. The ceiling joist nailed to the rafter tails forms a rigid triangle and that joist also connects the wall top to keep them from spreading apart. When the joist is left out there is nothing to prevent the outward spread of the wall tops. Over time more and more sag will develop. Yes, you have likely seen many builds with open ceilings. A few may have been built using a scissors truss. Google that if you are not sure what that is. Some, built with standard rafters, may last better than others because of no snow loads, the open distance may not be too great or maybe just dumb luck favors one over another. But none are good design. None will meet building code requirements.
I have seen a few wide open ceiling expanses that had steel rods across the walltops at intervals. The bolted sections actually pass through the walls and had reinforcing plates on the exterior. This type of thing usually has an engineer involved. Sometimes a few large beams can be used as wall top connections, at intervals across the space. Again, that is the realm of an engineer.
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razmichael
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# Posted: 12 Sep 2018 11:34am
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Can't you do this with rafters and a beam (rather than a ridge board)? You do need to make some design decisions to make sure you have adequate posts for the beam and they distribute the weight to the foundation but, especially for a 20' wide cabin, this should be doable. Ours is 16x24 (overhanging covered deck). Used a Gambrel rood with an LVL ridge BEAM (can't remember the specs but would depend on overall design anyway). Also used a 10' side wall height with dropped loft floor so our main loft is pretty close to being fully usable (estimate I can stand up in 12' of the 16' - so 10x12).
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snobdds
Member
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# Posted: 12 Sep 2018 11:44am - Edited by: snobdds
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Take a look at these two pictures. Some would say a cathedral ceiling is not possible because there is no rafer ties and can't be done. Well the two side supporting walls act as the tie to keep the main wall from spreading. Then the roof rafters lock everything in place with birds mouths. There is always more than one way to skin a cat. This was actually an architect that came up with this and then an engineer signed off on it. It was hard to build and I had some skeptics with people saying 12 high walls with no rafter ties and only floor joist spanning the distance was impossible...but it's so ridged and strong.
Edit. The pictures are not enlarging correctly, but there also in the link I posted above.
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Steve_S
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# Posted: 12 Sep 2018 12:33pm
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My cabin is 20x24, 2x6 stick framed on concrete slab. Walls are 8' tall (should have gone 10' 2x6). My roof is 2x8 @ 24oc (like the walls) with a centre 2x10 ridge board, all attached with Simpson strong ties and at wall with 3" birdsmouth cut & hurricane ties. Soffits & Eaves are 24" out from side. NB: by using the Simpson Ties & their Structural Screws you get a bit faster assembly time and a stronger connection. Lastly, I am in North Eastern Ontario Canada and subject to very severe Snow Loading in winter, so I made sure to meet & exceed codes whenever possible.
Final Note... My roof is NOT usual nor common. I have 7.5" of PolyISO between the rafters, reflective thermal barrier on the outside on top of the sheathing and a Texas Cool Roof built over that... I can only praise this type of roof system as it severely cut heating & cooling costs and made the home very livable... as well, the loft NEVER get's more than 2 degrees hotter than ground level !
REF to the Cool Roof System as described by a contractor who gives an excellent description & discussion on it.
http://www.houstoncoolmetalroofs.com/cool-roof-information/cool-roof-design-texas/
The reason I say 10' walls as opposed to 8', is that I have 1/2 the upstairs as a storage loft and it would have been far more practical / usable for more had there been a default 2' knee wall.... The floor for the loft would have been attached walls with ledger boards & sistered studs on ends per code requirements.
There are photo's and chat in my old thread on page 3, if your interested. http://www.small-cabin.com/forum/6_5643_2.html
Whatever you do, ensure that you comply with YOUR local Rules, Regs, Requirements & Codes, regardless of what anyone tells you on the web. I discussed my plans & ideas with my building inspector before I drew up the plans and we improved on them as it went with no issues, I got lucky with a good & reasonable inspector who was not afraid of new & unusual.
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NorthRick
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# Posted: 12 Sep 2018 01:49pm
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Quoting: ICC Technically speaking, you can not do a wide open, cathedral like ceiling space without using engineered trusses.
Not quite true. You can use a ridge beam as razmichael did. Posts hold up the beam and a properly sized beam holds up the peak end of the rafters. The walls hold up the lower end of the rafters. With this, the loads are all going straight down and there is no force trying to push the walls out.
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ICC
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# Posted: 12 Sep 2018 02:47pm - Edited by: ICC
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Quoting: NorthRick Quoting: ICC Technically speaking, you can not do a wide open, cathedral like ceiling space without using engineered trusses. Not quite true. You can use a ridge beam
You are absolutely correct; that is the problem with making a broad general statement as I did. I should have explained the ridge beam alternative, but didn't. Ridge beams do present many other design must-dos, like foundation support, mis span supports at times, etc. Sorry 'bout the slipup.
Quoting: snobdds This was actually an architect that came up with this and then an engineer signed off on it.
When an engineer does the calcs and can place their professional stamp on a design, things are good. Copying what can be seen from a distance can be frought with unknowns though. It is not a safe idea to simply copy what is seen; sometimes that may be okay, other times there may be details that can not be seen, the soil may be substandard, a host of variables. An engineered design is normally only approved for the specific site.
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