Knee walls / Let-in framing and the IRC/IBC (Plan Z010)

[Native_NM]

We have been in planning mode for two years.  I promised myself this would be the year!  We have the land, have the time, and maybe even the money!

I pointed my PE (who just happens to be my brother) to this site, as I want to use the 20x3Nx1.5 (Plan Z010).  Without having the plans or seeing the stamps, he could only make general comments.  He was generally very impressed, but did ask about the size of the knee walls in the loft.  He seems to think that living spaces under a sloped ceiling require a minimum side wall of 5 feet, and that there are some other size restrictions for the living space under the ridge beam. 

Also, he found one project where the builder notched the 2x6 sidewalls for a 2X ledger.  He told me that one can't notch more than 25%, or 1 3/8", on a 2x6 bearing or sidewall.    How do the plans address the knee walls?  It seems that the builders here are 50/50 platform/balloon frame.

To be fair he primarily works on commercial projects.  Has anybody else had to deal with these issues?  He told me he could do more research but it would cost me more beer.  Maybe we can address it right here. 

I will have to submit plans on whatever we build.   Maybe the side walls are already 5' on the plans, but in some projects they look shorter.  Or maybe he is wrong!   

Also, for anybody in NM, have you heard anything about a new requirement to have all plans stamped by a NM PE in addition to any other state's? 

[MountainDon]

Congrats!!!   

Re the engineer stamp....   From the CID website....
http://www.rld.state.nm.us/cid/planreview.htm

"The Handbook for NM Building Officials, published by the Board of Architects and Board of Engineers requires the single seal of an engineer or architect on projects which do not exceed a construction valuation of $400,000 and have a total occupant load of more than ten (10) but not more than fifty (50). The seal of both an architect and an engineer is required on projects with either a construction valuation of greater than $400,000 or a total occupant load greater than fifty (50). Occupant load shall be calculated in accordance with the current adopted building code."

So it appears that for small cabins and homes that is not necessary unless local building departments require an engineer or architect stamp.

[MountainDon]

Re: the let in 2x in a 2x6 stud. Depends on the strictness of the interpretation by the building department and/or inspectors. Local advise is usually the best when it comes to details.



other links of interest to NM
http://www.rld.state.nm.us/cid/permitting.htm

[Native_NM]

Congrats!!!   

Re the engineer stamp....   From the CID website....
http://www.rld.state.nm.us/cid/planreview.htm

"The Handbook for NM Building Officials, published by the Board of Architects and Board of Engineers requires the single seal of an engineer or architect on projects which do not exceed a construction valuation of $400,000 and have a total occupant load of more than ten (10) but not more than fifty (50). The seal of both an architect and an engineer is required on projects with either a construction valuation of greater than $400,000 or a total occupant load greater than fifty (50). Occupant load shall be calculated in accordance with the current adopted building code."

So it appears that for small cabins and homes that is not necessary unless local building departments require an engineer or architect stamp.

Thanks.  I heard a rumor that NM was looking at requiring a NM PE for all residential projects.  It seems overkill, but then nothing the state does anymore makes sense to me.

[Native_NM]

Re: the let in 2x in a 2x6 stud. Depends on the strictness of the interpretation by the building department and/or inspectors. Local advise is usually the best when it comes to details.



other links of interest to NM
http://www.rld.state.nm.us/cid/permitting.htm

Thanks, what about the knee walls?  Any guidance? 

[MountainDon]

There are a number of "depends" on the kneewalls. I don't want to venture onto that ground myself. If you were to use a ridge beam (not a board) or trusses that would remove the problem of outward forces on the sidewalls though.

There are other states that require an in-state professionals stamp on any plans. Some of those are the result of in state lobbying efforts from the various architect or engineer societies, I'm sure. Some of it may be a CYA routine. I haven't pulled any permits recently, but in the past the local building department looked over my home drawn plans, penciled in any changes they wanted and approved them. Same thing for a friend who went through the state CID. Do you have a local or will yours be CID?   For my Jemez area it was a combination of local (basic zoning permit) and CID (building plans approval permits).

[Native_NM]

There are a number of "depends" on the kneewalls. I don't want to venture onto that ground myself. If you were to use a ridge beam (not a board) or trusses that would remove the problem of outward forces on the sidewalls though.

There are other states that require an in-state professionals stamp on any plans. Some of those are the result of in state lobbying efforts from the various architect or engineer societies, I'm sure. Some of it may be a CYA routine. I haven't pulled any permits recently, but in the past the local building department looked over my home drawn plans, penciled in any changes they wanted and approved them. Same thing for a friend who went through the state CID. Do you have a local or will yours be CID?   For my Jemez area it was a combination of local (basic zoning permit) and CID (building plans approval permits).

The guidance right now is go through CID if you ever think you might want to sell it, finance it, or insure it.  I plan to go through CID.

[PEG688]

 You might print out or look at this "Letting -in ledgers for floor joist" , in the  'sticky' section of this sub forum  ,  braces thread , we whipped that horse till it was darned near dead.

But your thread may breath new life into that near dead horse.


 http://countryplans.com/smf/index.php?topic=1418.0  

[Don_P]

No portion of the REQUIRED floor area may be less than 5'. After meeting the minimum room area it can slope to the floor if you want. R305

Notching, he is correct technically. Look at the right side of the drawing in fig R602.3(1) for the ledger. Notice that is not a kneewall situation, the rafters above are not thrusting. The kneewall is not prescriptive, he's an engineer. I'll chip in on the beer if he'll run the numbers on the combined bending and axial stud stresses.

On that width building and roof pitch if the kneewall is 5' the rafter ties can be in the lower third of roof height and it could be platform or balloon framed by the codebook. From 5' down to zero knewall height it is technically an engineer required solution the way I see it. A ridgebeam is another alternative.