IRC continuously sheathed exterior Question

[Loui1]

I am new to the IRC, looking at designing single family residences, and am trying to figure out what is required for exterior sheathing and lateral load resisting system. The builder wants to sheath the entire exterior skin of the house in 15/32" OSB Sheathing. Method 3, specifically R602.10.5 "continuously structrual panel sheathing" appears to say that if you fully sheath the exterior of the building, you wont have to worry about hold downs, or specific engineering calculations if you follow the perscriptions. It sounds great to me, but I am skeptical. If anyone can give me the lowdown on this I'd appreciate it. I'm used to the IBC, designing much larger structures and dont want to go overboard. Heck, it looks like the drywall can be used...why would an engineer be used to design a house then???

 

[CJJS]

It's rare that an engineer is used to design a house here in South West Ohio. Building designers are typically used. And it's rare that you even see a design with an architects seal.
I recently went to a Code Officials seminar where they talked about enforcing that provision of the code. I have not yet seen it on any drawings I have dealt with.

 

[SlideRuleEra]

In South Carolina most residential and certain other buildings that have less than 5000 sq. ft. and are less than 3 stories tall do not require an engineer's involvement.

http://www.SlideRuleEra.net

 

[Loui1]

So any help with R602.10.5? Do I need to detail out shearwalls or not?

 

[Loui1]

BTW, this is in the midwest. Not coastal or seismic.

 

[CJJS]

I would check with the local building departement in which the residence is being built. See if they have adopted that part of the IRC code.
Here in Cincinnati, they are beginning to require building designers to simply illustrate the shear walls on the plan, although I have yet to see a plan with that on it.

 

[SperlingPE]

Contact local authority. Most framing for single family homes that are under a certain square footage and follow the prescriptive measures in the code do not require any detailing or design. However, if you are doing cutom work and run into an unusual situation or if unable to follow the prescriptive measures, engineering would be required. This is the stance that the local authorities take in my area.

 

[jhoulette]

In Colorado all single family homes (and larger structures) must be designed and stamped by a PE. We deal with some high wind (typical 110 mph Exposure C) along the front range of he Rockies.
Loui1 - You should be careful to simply use the prescriptive method in the IRC. Many houses do not meet the requirements, such as walls at every 25ft, walls located within I believe 8ft of the exterior wall, and long enough wall panels. I deal with a lot of homes that only have one or two wall segments that are about 3ft long along the front of the house including the 16ft garage door. It's tough enough to try and get the walls to work with nailing at 3" o.c. and use a typical embed strap holdown (Simpson STHD10RJ). Your only hope is that the architect gave you enough walls to meet the requirements for prescriptive design (I know most of the time I'm not so lucky). Check out

http://www.apawood.org

they have a lot of free publications you can download. I know they just released one on continuously sheathed houses.

 

[jhoulette]

Oh and you may also want to talk to the builder about using 3/8" or 7/16" OSB instead of the 15/32". You get the same shear value per footnote "d" as long as either your studs are at 16" o.c. or you have them place the panels length across the studs. But I should warn you that 3/8" can get too small and the possibility of "waves" can happen. 7/16" is typical in my area.

 

[HouseBoy]

Loui1
I am familiar with the IRC provisions regarding lateral wind resisting systems for houses. There are a number of provisions that have always been in the building code but that have ben largly ignored. There has been a push recently (in Ohio they just adopted the new IRC Statewide) to recognize this part of the code so there has been some new attention to it. A good referenc is this:

http://www.apawood.org/level_c.cfm?...s&pD=Yes&pF=Yes&CFID=3949905&CFTOKEN=30472477

To answer your question, if wood sheathing is used on the whole exterior, the code allows for a reduction in the length of shearwalls that would otherwise be rrequired. There seems to be a great reluctance on the part of many builders to utilize anchor bolt type hold-downs. There has also been much development on improving garage walls where there are limited length walls available.
Let me know if oyu can't get to the link. It is an APA site and there is much info relating to this on that site.