Tiny Homes as Modular Housing
In late December, I was fortunate to establish a call with members of the International Code Council (ICC) in which other dedicated members of the Tiny Home Industry were invited to participate in the standards development process for Off-Site Modular Construction (OSMC).
From the standpoint of our Uniform Compliance Initiative, OSMC is a boon for tiny homes as it addresses some of the biggest challenges we’ve faced as an industry:
- Off-site prefabrication and construction of an
- Easily transportable residential dwelling unit that
- Carries bona fide records of compliance which
- Guarantees rights of use as housing.
To be clear (by using cliches) OSMC isn’t a silver bullet, but it looks like the missing link.
Standards Development
As a tiny home design and planning professional, I am participating in OSMC development as an “interested party” and submit the following for consideration on behalf of our industry:
Relocatable Residence
Given the application of OSMC for both residential and commercial applications, it seems reasonable to define a class of modular housing units that may conform to specifications that allow for their reuse in multiple locations.
The term “Relocatable Residence” will likely parallel the existing commercial application for a “Relocatable Building,” the general premise of which will likely have great similarities in design, manufacturing, inspection, registration, permitting, placement, and certification for occupancy.
Housing and Community Development departments already oversee modular home programs as Industrialized Buildings and Factory-Based Housing, manage the rostering of Third Party Inspection Agencies, and address statewide regulations.
While the Tiny Home Movement illustrates the need for flexible housing which includes compelling use case scenarios for temporary, emergency, semi-permanent, and permanent housing, “movable tiny homes” seem stymied from large-scale adoption as housing due to their use of off-site construction without a broadly used uniform means of qualifying their conformance.
Bottomline: OSMC offers an opportunity to introduce a new housing class as a Relocatable Residence and pathway of residential compliance for housing produced off-site that may be used in a variety of locations by multiple home owners during its lifecycle.
Appendix Q
Appendix Q (A.Q.) was introduced in IRC 2018 and has been strengthened for IRC 2021.
A.Q. provides a series of exceptions for items that don’t appropriately scale into residences with small footprints of 400 sqft or less. Additionally, A.Q. offers relief from other aspects of home design that limit living space in height restricted residences, which is often the case for Accessory Dwelling Units, and especially applicable to a Relocatable Residence during transport.
A.Q.’s benefit here leverages a slight adjustment to ceiling heights on main floors, as well as the use of an elevated loft as sleeping quarters. To further save space without sacrificing safety, A.Q. includes appropriate egress provisions from lofted sleeping spaces.
A.Q. has proven its benefit to “movable tiny homes” and illustrates how OSMC-based units may travel from manufacturing center to installation sites as housing modules of closed construction that are quickly and easily moved and available for use immediately after relocation.
Bottomline: At a minimum, it seems appropriate to include a pointer in OSMC to IRC Appendix Q that introduces its application to modular “tiny home” design that maintains correlation between IRC housing and OSMC standards. It is also possible that text and standards from Appendix Q may be included directly within OSMC as an appendix, or within the body of the standard ensuring A.Q. remains broadly applied to tiny-sized modular housing units.
Interior Air Quality
Tiny-sized homes are inherently small in volume and thus perform differently than average sized homes when considering occupant health from interior air quality.
There are many contributing factors to consider for a tiny-sized Relocatable Residence or site assembled unit including its air tightness, number of occupants, use of gas-burning appliances, and more.
Bottomline: It seems reasonable to give attention to unit design in a prescriptive sense, plus a means of calculation and/or measurement of unit performance in terms of air exchanges per hour, air quality monitoring, noxious gas detection, and other critical aspects that could affect occupant health as related to building envelopes of different volume.
Energy Efficiency
Related to the above, smaller units have different performance characteristics.
This is especially true where use of prescriptive standards (e.g. 2×6″ for walls to achieve minimum R-values) create an excessive deviation when scaled into smaller sized dwelling units.
Use of prescriptive codes for standard sized homes can beget an over-built home in a smaller size that results in increased cost, greater travel weight, and excessive material use than is necessary to achieve the same results.
Bottomline: In addition to baseline standards, calculations and tests may be outlined as “alternative methods” that meet the intent of the code where energy performance is concerned for a range of building types and envelope sizes.
Chassis Design
There are variances between what seems most typical for Relocatable Buildings (I-beams supporting conventional floor system) and what has become usual and customary for Movable Tiny Home construction.
Tiny home methods effectively lower the main floor of a tiny-sized Relocatable Residence by using the chassis as the floor system and insulation cavity. The net result is a reduction in ground-to-main floor height that may be used to lower overall unit height and lessen wind resistance during transport.
When building requirements provide an allowance of Appendix Q for small space design, the reduction in ground-to-floor height is critical for providing compliant minimal living space in elevated sleeping lofts.
Once subfloor, walls, and roof members are installed, the dwelling unit and chassis comprise a composite structure from which wheels/axles and tongue/coupling mechanisms may be detached. Additionally, it is common practice for a tiny home chassis to include integrated fastening points for ground anchoring to meet foundation requirements.
Bottomline: Since engineering can be provided for the chassis and outer envelope to meet requirements for weight distribution, load bearing, envelope affixation, and resistance to high-velocity winds, it seems reasonable to either define alternate methods or (at least) ensure that specifications do not preclude the use of such increasingly common practices that aid in developing more innovative housing designs.
New Tool in the Box
Off-Site Modular Construction fills the void between non-compliant “no code” THOWs, certified Tiny House RVs, HUD based Manufactured Housing, and site-built homes.
OSMC provides a way to produce Tiny Homes in greater volume and lower cost while bringing a level of legitimacy that opens the door more broadly for tiny community development, tiny-sized principle residences, easily installed accessory dwelling units, and a fully-compliant “movable tiny home.”
Another big win for tiny home builders and buyers: Funding and financing will follow.
New Way to Go Tiny
Modular homes are typically factory-built, with costs and requirements that greatly exceed those used by Tiny Home RV builders. That said, the prospect is greater for all when leveraging OSMC for designing, building, placing, and using a tiny home as a Relocatable Residence.
As a long-standing advocate for tiny homes as portable housing, an educational platform, a tool for supporting disaster relief efforts, and means to create one’s own home, I remain a highly invested interested party in our collaborative success.
Stay tuned for updates and progress reports.
Live Large — Go Tiny!
Thom Stanton
