i have a few questions about codes for single story res. construction. this will likely get long.
a little history:
i design and build dental offices here in CA, and have been doing this for quite some time with great success.
i have also drawn a number of plans for minor single story residential remodels as well as having been on the field for 20+ years for the construction.
in other words, i am not new to this.
at this time, i am doing an addition on my own residence. this makes this particular job a bit more personal. i am currently having some difficulty with plan check in my town. it seems that there are some differing interperitations of the code.
i am adding on apx. 450 s.f. to my 1100 s.f. home.
the addition concists of adding a master bedroom/bathroom/closet, and extending the living room apx. 5 feet.
now, one of the first issues is shear panel for the new bedroom area.
LA has created these type V sheets to help owner builders in making their drawings comply with code. there seems to be a discrepency in the type V sheet, and the actual code.
the type V sheet has a drawing of “alternate bracing” referring to cbc 2320.11.4 but it has in parentheses that this is for 1 story “u” occupancies only. now the same code number from the code book makes no such reference. rather it states:
there is no mention of “u” occupancy in the book.
so which is correct? i would immagine the book.
now, onto another bit of confusion on the subjet of shear.
referring to the cbc 2320.11.3 on the type V drawings provided by the city, there is showing a 4’ shear pannel on each and every corner of a square box. the shear is shown right on the corners in each direction.
this makes no sence to me, as i am sitting in front of a window right now that is in the very corner of my room as i type this.
the plan checker has interpereted this sketch as the law. he is not allowing me to have a window, or door within 4’ of any corner of the room being added.
i have a huge problem with this as it completely ruins the design of the room. it forces me to remove one window, move another into the shower, and shrink another by almost half.
again, i refer to the code book for the same code number: cbc 2320.11.3
and this is how it reads:
now i realize some of these methods do not apply to my seizmic zone, but i am reading this in a way that indicates the fact that the beginning of the shear pannel must be within 8’ of the corner, and the next piece within 25’ of that one.
am i interpereting this correctly?
i have no problem over building this thing as it is my own house. i do have a problem with being told i cant have a window or door within 4’ of a corner.
sorry to hit you guys with so much at one time. please be patient with me.
the next issue is the extention of the living room by 5’.
the way i handeled this is to remove the 23’ living room wall, and support the existing ceiling, and roof framing with a parallam beam 5.25x16" which was engineered suitable for the weight and deflection by a weyerhauser engineer.
the existing roof is 3:12 with 3 tab shingles in an area with littl to no rain and no snow.
the existing ceiling members (2x4) are attached to the parallam with simpson 2x4 hangers on each member. the same for the roof members. each one gets a hanger to the face of the parallam.
now on the new side of the parallam, each ceiling member gets the same treatment. 1-2x4 hanger for each member.
the 2x6 roofing members will now run from the new wall over top of the parallam to create a 2.5:12 shedding type roof.
i sure hope this makes sence. i’ll get some detail pics up soon.
now, bear in mind that there is a contnuous footing under this parallam, as there once was a bearing exterior wall in its same location. the footing is a minimum 12"x12"x24’.
there is a question in the mind of the plan checker as to the adequacy of this footing for the load of the parallam.
the parallam is supported on each end of its 23’ length by a 4x6, and the appropriate simpson post cap.
please advise me here. am i wrong on this one, or is the plan checker thinking too much into it?
to top it off the plan checker i was working with was either fired or quit. so now i have to start over with a new one. what makes it worse is that the new one is following the previous checkers red lines no matter how off base they are.
compound that with the fact that there is only one plan checker in the building and no one to supercede him, i am in a bit of a quandry.
if anyone has any insight on my problem, please help me. i am very anxious to get this thing moving.
i know i pretty much dropped a bomb on anyone willing to read this LONG post, but would be very much appreciative of any insight.
I think the problem is that you’re relying too heavily on “boiler-plate” drawings from the city/township. These are used when a homeowner is making additions without the benefit of hiring a structural engineer, and using conventional methods of framing and shearpaneling.
There are engineered systems that can be used to replace conventional shear walls, but they must be approved by a state licensed SE (the city will not do this for you).
Without this “enhanced” design approval, you are stuck with the boiler-plate drawings. The “plan-checkers” allow very little wiggle room unless there’s an engineer willing to take the liability.
arent the plan checkers still required to follow the specifications laid out by the code book? for example the shear pannel starting within 8’ of the corner?
even the boiler plate drawing shows this. he is making his own rules requesting the pannels be on each corner.
Conventional methods can be replaced by engineered designs. Simpson makes steel shearwalls to replace conventional-lumber shearwalls, and they don’t require the same width to develop the same strength. However, they do require a different footing and hold-down design.
Erik – you stated that you are in L.A. The code items you quoted are from the CBC. The California Building Code is a variation of the Uniform Building Code. However, the city of L.A. has the L.A. City Building Code and the county has the L.A. County Building Code. Each jurisdiction is allowed to require additional items above a beyond the minimum code that the state requires. Both the city and county of L.A. have made major changes to the code. These changes are so significant that I know some engineers that refuse to do work in these jurisdictions.
As to your question regarding the windows in the corners: the existing house was built under a different code or with engineered plans or both. Every addition to an existing house has to meet the current code. If the required changes are too much, then I would suggest hiring an engineer.
As to the footing, the plan checker is correct. Unless you hire an engineer to do a soils report, the maximum assumed allowable soil pressure is 1,000 psf. With a 12” wide x 12” deep footing your maximum allowable point load is just over 3,000 lb. That is a very light point load for a 23’ long beam. Check the beam calcs reaction.
Most building departments won’t accept plans unless they have an engineer’s stamp.
I provide structural engineering for residential projects, so feel free to call our e-mail if you need any additional help.