Deciphering codes for small prefab cabins: HUD vs. I-Code vs. ANSI A119.5
The world of small prefab structures can be confusing when trying to understand what each builder specializes in or what the regulations are for your own property. The first step is to be able to grasp the three main ‘buckets’ of regulatory code that a manufacturer may be building to.
While there are lesser used and region-specific programs, for the purpose of this article we will look at the three prominent codes that govern the construction and safety of small buildings in the USA: HUD (U.S. Department of Housing and Urban Development), I-Code (International Code Council), and ANSI A119.5 (American National Standards Institute’s Park Model RV Standard). Each code serves a distinct purpose and sets specific guidelines for how a building is constructed. Let's explore the differences and implications of these codes to help you make informed decisions in your purchase of a cabin or ADU.
HUD (U.S. Department of Housing and Urban Development):
HUD, or the U.S. Department of Housing and Urban Development, is one of the executive departments of the U.S. Federal Government. They have developed standards for a category of building called manufactured housing.
What is it?
Some people may know these by older terms such as mobile home or trailer home. Mobile Home is actually a term used prior to 1976 when the HUD Code went into effect. These structures were initially targeted at people who favored mobility (thus trailer home), and were eight feet or less in width. By the 1950s this industry had shifted toward more permanent low-cost housing options and HUD guidelines (sometimes referred to as H-Code) now have a minimum of 12 feet wide and 400ft2.
The HUD standards are a strict, national standard that requires the units to be manufactured in specific HUD certified facilities.
We will see later in this article that Park Model RVs now occupy this original ethos.
What does it mean for me?
Many jurisdictions do not allow manufactured homes. Some have very strict policies toward single-wide (12-18 ft wide), but are more accepting of double wide (20-36 feet wide). Double wides use a modular building technique to manufacture each half separately and connect them together on site. Manufactured homes must be built in HUD certified facilities so cannot be built by most contractors or construction companies.
I-Code (International Code Council):
The International Code Council (ICC) develops a series of building codes known as the I-Codes, which are widely adopted in the United States and a few other countries. The I-Codes cover various aspects of construction and safety and are what any ‘typical’ building you have encountered is built to. This is what most people think of when they hear the term building codes.
What is it?
The I-Codes offer comprehensive building and safety standards that encompass aspects such as structural design, electrical systems, plumbing, and fire safety. I-Codes are ‘model codes’ meaning that they are suggestions for best practices and are not specifically enforceable right away. Each local jurisdiction such as a city or county can adopt some or all of these codes. This means that though the ICC releases new versions every three years, different cities may be using any past version, or may be creating their own codes entirely.
What does it mean for me?
It is important to understand that each municipality will have its own adoption and interpretation of the I-Codes (or something similar). Because of this, it is important to communicate with the Building and Zoning departments when making decisions about your property. Many jurisdictions have a minimum square footage for a primary residence, and have a specific number of allowable Accessory Dwelling Units allowed for each property. These single family homes are generally built using the IRC I-Code (International Residential Code).
IRC Appendix Q
One specific callout to the I-Code that is relevant to those reading this article is the IRC Appendix Q: Tiny Houses. The ICC has acknowledged the growing demand for small structures and has now put in place specific requirements for houses that are 400 square feet or less.
Different builders have different areas of focus, and it is important that your builder understands all of the code requirements for what you are specifically interested in building.
ANSI A119.5 (Park Model Recreational Vehicle Standard)
ANSI A119.5, developed by the American National Standards Institute in partnership with RVIA (The Recreation Vehicle Industry Association), specifically addresses the construction and safety standards for park model RVs. This is what many people refer to as Tiny Homes on Wheels (TOWS). It offers a dedicated set of guidelines tailored to the unique characteristics of these recreational vehicles.
What is it?
ANSI A119.5 offers a consistent and uniform set of recreational vehicle standards that manufacturers and owners can follow across the country. This standardization simplifies compliance and ensures a common baseline for safety and construction quality. Manufacturers of park model RVs are encouraged to adhere to ANSI A119.5 to ensure that their vehicles meet recognized safety and quality standards. Compliance with this standard provides assurance to buyers that the RV meets industry-specific requirements.
What does it mean for me?
If you are looking for a portable cabin, you will likely find many Tiny Home builders. These builders should be building to the A119.5 standard and getting these RVs third party certified in order to receive a title and VIN number.
These structures are actually considered a recreation vehicle. Many jurisdictions and HOAs have strict rules about how many (if any) park model RVs are allowed on a property and how long someone can occupy them.
Conclusion
At Further Society we design our structures first to I-code, but always with the considerations of ANSI A119.5. Because of this, we are able to make very minor changes to fit into either system.
By gaining a clear understanding of these regulations, you can confidently navigate the landscape of small buildings, ADUs, and cabins, ensuring compliance, safety, and quality in your construction endeavors. As always, we are here to help guide you through this process.
