Some tiny house builders follow particular building codes to be certified in order to meet minimum requirements of a standard house. Not all tiny house builders may follow these codes. Inquire with your builder as to what codes are followed for your tiny house.
The International Residential Code (IRC) is a comprehensive, stand-alone residential code that creates minimum regulations for one- and two-family dwellings of three stories or less. It brings together all building, plumbing, mechanical, fuel gas, energy and electrical provisions for one- and two-family residences. The IRC also provides a prescriptive approach (i.e., a set of measures) and a performance approach (i.e., energy modeling) for determining compliance.
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The appendix addresses ceiling heights, sleeping lofts, loft access, emergency egress and rescue, and many other details. By removing all of the other issues that typically cause challenges for tiny house builders, each owner can use this appendix, along with section R104.11 to work with their building department and/or an engineer to create a foundation system that meets the intent of the code and does not require the complete removal of the trailer tires.
Tiny house Appendix Q does take away the vast majority of the challenges a moveable tiny house would face, leaving the chassis/trailer as the last major potential roadblock. As such, builders and owner builders alike can submit an application for the foundation design through Section R104.11 of the IRC entitled Alternative materials, design and methods of construction and equipment. This application simply needs to show how the chassis/trailer can be incorporated into a suitable foundation to meet the intent of the code. This design could likely draw heavily on Appendix E: Manufactured Housing Used As Dwellings, as the majority of that appendix focuses on mounting a chassis/trailer to a code approved foundation for manufactured housing. This is a great place to start for using the code itself to support your design and long term plans.