Effective Date Dec. 6th,  2019

Written by Janet Thome

The state of Montana has adopted  Appendix Q Tiny House.  The effective date is Dec.6th,  2019. All jurisdictions in Montana will have the option to adopt it as well.  Appendix Q has been adopted without amendment.

Appendix Q-Adopted  into  the 2018 International Residential Code ( IRC ) building code to provide regulations and standards for tiny homes on a foundation that is 400 square feet or less

Appendix Q relaxes various requirements in the body of the code as they apply to tiny houses that are 400 square feet or less.
Attention is specifically paid to features such as compact stairs, including handrails and headroom, ladders, reduced ceiling heights in lofts and guard and emergency escape and rescue opening requirements of lofts.

The International Residential Code is a comprehensive, stand-alone residential code that creates minimum regulations for one-and two-family dwellings of three stories or less.

The IRC brings together all building, plumbing, mechanical, fuel, gas, energy, and electrical for provisions for one-and two-family residences.  Appendix Q was adopted to the IRC building code standards through the ICC Code Development Process.

Jurisdictions may use Appendix Q as a model code to adopt, reference, or amend. Builders or even jurisdictions that have not adopted the 2018 IRC or the Appendix, can seek approval ”on a project basis through the alternative materials and designs provision” in the IRC.-David Eisenberg,  co-author of The Strawbale House Book.


(a) Appendix Q, Tiny Houses. Appendix Q may be adopted by a certified city, county, or town building code jurisdiction. Tiny houses do not meet the building code requirements for commercial or business occupancy and are therefore prohibited for these types of uses. The department will apply Appendix Q to factory-built buildings which meet the definition of a tiny house as having 400 square feet or less in floor area excluding lofts, and which are intended to be mounted on a permanent foundation and used as a single-family dwelling.

Building Code Documents

Note: I spoke to Tim Lloyd again on Nov. 29th and he clarified the terms regarding commercial use of tiny homes. Long term rentals are allowed, they just do not want nightly rentals like an AirBnB.

Tim Lloyd Is The Bureau Chief

State Of Montana Labor And Industries

Montana Secretary Of State:

Montana Appendix Q Tiny House

24.301.154 Incorporation By Reference Of International Residential Code