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SonnyB
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# Posted: 10 Jan 2012 08:24pm
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I have been checking the site out for a few months and really like it. So I bought a little over 4 acers in NGA mountains and am thinking about building. The question I have is I am thinking of building a 16x32 1 1/2 story with 12 foot walls because I am 6' 4" and would like the extra height in the loft. Do you think I should go down to 10' walls or is 12' ok? Tell me any pros or cons! Thanks for the help.
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MtnDon
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# Posted: 10 Jan 2012 08:41pm - Edited by: MtnDon
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Question: do you have to obtain a building permit and will there be inspections of the framing? If so, the plan will not likely pass as you describe. 10 or 12 foot tall side walls with a loft at the 8 ft mark can run into issues with potential wall spread because of the rafters pushing outwards on the tops of the walls. For that reason codes say 'no' to such things. Many do it when they don't have permits and inspections to deal with, but it's not recommended.
Using a ridge beam instead of a ridge board can correct that problem. That requires a clear load path down the end walls to the foundation and ground.
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SonnyB
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# Posted: 10 Jan 2012 08:49pm
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I will have to get it permited but when I told them I was putting a loft in it the permit guy said it should pass. I am meeting with him next week to go over a few things. Even with a loft you think it would be to much outward pushing? Thanks!
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trollbridge
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# Posted: 10 Jan 2012 10:40pm
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May I suggest 10' walls and a shed dormer. This is what we have done in a portion of our loft(a little different 'cause our cabin is 24 wide) but we have 2 sons both over 6'5" and neither is remotely close to being uncomfortable up in our loft.
Also welcome! Good luck when you meet with the permit guy next week :)
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MtnDon
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# Posted: 10 Jan 2012 11:36pm - Edited by: MtnDon
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I'm basing that answer of mine solely on the requirements of the IRC, the most commonly used building code in the USA. The only way to know for certain what the local official will enforce is to show them plans, even pencil sketches or simply have a conversation.
The sticking point, if they choose to go by the way the code is written, is what they will want for rafter ties. I'm not sure of level of expertise so I apologize if you know the following.
Standard rafters, where the tips meet on a ridge board and the tails rest on the side walls, put the entire weight of the roof on the sidewalls; half on each wall. That includes weight of materials and weight od snow,rain,wind force. If the roof has a 12/12 pitch (45 degree angle) then half the weight presses down and half pushes out, more or less. If the roof is less steep, more pushes out, if the roof is more steep less pushes out.
Building code requires the rafters have collar ties and rafter ties. Collar ties hold the peak of the roof together. They must be in the upper third of the rafter/walls triangle. The rafter ties hold the upper end of the walls together. Rafter ties must be in the lower third of the rafter triangle. See illustration below.
There is no provision for lowering the rafter ties down into the wall framing and making them become a loft floor. That's where the code will catch your plan if it is enforced in the usual manner. This is something you should ask; explain how the loft and roof is planned. Perhaps make a few sketches that clearly illustrate the planned loft floor and roof. The last thing you want is a misunderstanding when it comes time for them to inspect the framing.
Back to those outward forces on the top of the wall... The higher the wall above the loft floor the greater the risk of those vertical "stubs" being loaded greater than they can resist. If there were no code permits involved people do get away with it. Most of the time. And perhaps trouble does not show up immediately, possibly never. But it is poor engineering design.
Raised walls like that are frequently called kneewalls. A tall kneewall can work well if used with either: (a) factory made roof trusses. Ask about attic trusses or possibly scissor trusses. (b) a ridge beam instead of the normal ridge board. Ridge beams are more massive, frequently are glulams or other engineered products. They support 50% of the roof load and transfer that down through columns in the end walls to the foundation and ground. They require calculations to be sized properly. They eliminate the outward forces on the wall tops.
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MtnDon
Member
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# Posted: 10 Jan 2012 11:42pm
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After you talk with the permit guys it would be interesting to know what they allow/decide.
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SonnyB
Member
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# Posted: 11 Jan 2012 09:41pm
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Ok talked to the county permit guy and he said I could go with 10' wall with a loft with no problem. I love it when its easy to work with the county! I am thinking about going to a 20x24 instead of a 16x32. Give me your ideas!!!
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MtnDon
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# Posted: 11 Jan 2012 10:00pm
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You are fortunate!! Run the extra width by them as the forces go up as the building get wider.
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SonnyB
Member
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# Posted: 12 Jan 2012 08:02am
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Permit guy said I could go up to 24x24 with 10 foot walls. Going up to the land this weekend and will start laying out where the cabin will be built!
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trollbridge
Member
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# Posted: 12 Jan 2012 08:26am
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Have fun! Glad it went well.
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SonnyB
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# Posted: 9 Mar 2012 03:06pm
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Change of plans again! Permit people said no problem with any changes so I told them I want to go with a 20x32 with 12' front and back walls with lofts at both ends! I am going to start putting post in the ground this weekend!!
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