1. Do all shear walls require a metal mesh or continuous all thread or rebar through them?
No, Wall A in TABLE AU106.11(1) applies to braced wall panels (shear walls) in Seismic Design Categories (SDC) A, B and C. Though TABLE AU105.3 would govern for most designs, TABLE AU105.3 allows for Wall 1 in SDC A, and Wall A in SDC A and B. All of these walls mentioned here do not require a metal mesh or continuous all thread or rebar through them.
2. Is it true that any shear walls that exist in zones B onward will require some sort of mesh or rebar reinforcement with all thread connecting foundation to bond beam, therefore, the only case where this is not required is zone A?
No, as stated above, TABLE AU105.3 would govern for most designs, TABLE AU105.3 allows for Wall 1 in SDC A, and Wall A in SDC A and B. The designer could also choose to hire an engineer to attempt to conduct a custom design under the Alternative Materials and Methods chapter of the International Building Code (IBC), likely utilizing geometry changes, that may apply to a different and possibly straw based reinforcing strategy to resist out of plane loading so that Wall A in TABLE AU106.11(1) would apply and allow use in Seismic Design Categories (SDC) A, B and C.
3. Now that the Cob Code Proposal is approved into the International Residential Code, what's next?
The RB299 Cob Construction Proposal was approved by ICC voting members (mostly building officials) in the November Online Governmental Consensus Vote and it will become part of the 2021 International Residential Code (IRC). The IRC is a model code with no legal standing of its own, but it is the basis for the residential code in virtually every jurisdiction in the United States. State and local jurisdictions have their own code adoption cycle, that is typically triennial and typically one year after the ICC triennial code cycle.
For example, the State of California will use the 2021 IRC for its 2022 California Residential Code (CRC). The 2022 CRC goes into effect Jan 1, 2023. California may or may not adopt the cob appendix. If not, local jurisdictions are free to adopt it. Local jurisdictions would also be free to adopt the appendix ahead of the State of California’s code adoption cycle.
4. Can my jurisdiction adopt CRI Cob Building Code as approved by ICC?
Any jurisdiction can adopt anything they want from any source. CRI can direct jurisdictions to the link on CRI’s website for the revised proposed Appendix U (our public comment) and they can use that as the basis for adopting it if they choose. CRI Cob Building Code doesn’t need to be approved for a jurisdiction to adopt it, but they would be more likely to adopt it if approved by ICC.
5. Cob Q&A with Michael Smith
GreenHomeBuilding.com conducted a Q&A with CRI Board Member Michael G. Smith. To read more, please see here.
6. Any cob videos with Michael Smith?
Yes! Please see StrawClayWood.com.
7. Are there curvatures and wood column embedment in the Cob Code?
There are curvature options in the code as well as wood column embedment.
8. If you include rebar in the code everyone will build with it. Does your code discuss the dew point in the wall caused by the rebar?
1) A wall option exists in the proposed cob code without rebar. It is appropriate in some building designs and locations, relative to design wind speed and seismic risk. So not everyone will build cob walls with rebar. Only when they choose to or when the situation requires it.
2) Rebar embedded in the foundation that extends into a cob wall can exhibit a lower temperature than the surrounding cob material. That temperature could be lower than dew point and condensation around the rebar is possible. However, the amount of condensation will likely be small, and clay in the surrounding cob is excellent at managing moisture. The clay will attract moisture away from the rebar, as well as the straw in the cob, protecting both. Note that a similar dew point dynamic sometimes occurs with rebar in reinforced concrete or CMU walls. In that case the free lime or cement in the concrete or grout protects the rebar from significantly rusting. In a cob wall the clay performs that function.