How to build a tiny house

Step 1: Choose the route before the floor plan

Most tiny house plans online are drawn for a trailer. Most zoning codes are written for houses on foundations. Choose your route before you buy plans, because it decides which rules your design must meet.

The trailer route has the hardest last step. Boise, Idaho, describes travel trailers, fifth-wheel trailers and park model RVs as temporary living quarters for recreational, camping or seasonal use, not year-round dwellings^[1]. Albion, Idaho, requires RVs, park models and tiny houses on wheels used as dwellings to be in an approved RV park^[3]. Boise does allow certified tiny homes on wheels in some zoning districts since July 1, 2025, certified to the NOAH+ standards or other standards the city adopts^[1].

A state-approved factory home is the third route. In Colorado, the Division of Housing approves the plans of state-certified Tiny Homes before they are built; they are approved for long-term living, have a permanent chassis, and can go on a permanent or temporary foundation^[4].

The rest of this guide follows the site-built route.

Step 2: Confirm the zoning

Before drawing anything, find out whether your lot may hold a tiny house, and as what. Boise asks people to check with its planning and zoning division before submitting for a building permit^[1]. Albion shows the kind of conditions a city can set: a conditional use permit, the tiny house on its own lot, the zone's setbacks, two off-street parking spaces, fire access under the International Fire Code, and connection to city water, sewer and electricity^[3]. On a lot that already has a house, the tiny house is usually an accessory dwelling unit, under different rules; see the ADU permit page.

Step 3: Design to the tiny house rules

The code's tiny house appendix is what makes a 400-square-foot plan workable. It applies to dwellings of 400 square feet or less in floor area, excluding lofts, and the rest of the residential code still applies^[2]. Design to these limits, as Boise applies them^[1]:

The obstruction rule is the one that ruins a nice section drawing: a beam that dips below 6 feet 8 inches in the living room breaks the ceiling height rule even if the ceiling itself is higher^[1].

Check your own state's version. The appendix is not mandatory unless the adopting ordinance references it^[2], and states amend it: Washington's version sends loft ceiling heights to the main code and adds an air leakage limit of 0.30 cubic feet per minute at 50 pascals per square foot of the dwelling enclosure, with testing^[2].

Step 4: Foundation and utilities

A permanent foundation is what makes the tiny house a building. Boise states that tiny houses need to be on a permanent foundation^[1], and Albion requires a permanent foundation and connections to city water, sewer and electricity^[3]. Size the foundation for your soil and your frost depth as the local code requires; that is where a small house has the same obligations as a big one.

Plan the utility routes on the site plan at the same time: the water line, the sewer or septic connection and the electrical service all cross the yard, and each is reviewed.

Step 5: Frame, close in and finish

From here, a tiny house is built like any small wood-frame house: walls, roof, windows and doors, then the rough plumbing, electrical and mechanical work, insulation and finishes. In small spaces, plan the ventilation early: Washington's version of the appendix requires whole-house mechanical ventilation when a tiny house meets its tight air leakage limit^[2].

Step 6: The inspections

Because a tiny house on a foundation is a dwelling, it goes through the inspections of a dwelling, stage by stage, before it can be occupied. Factory-built units go through the state's process for the unit and a local inspection for the placement: in Boise, modular and manufactured tiny houses must be permitted by the state and by the city to be placed on a foundation, and any structure or addition built on site needs plan review and a building permit^[1].

Do you need a permit to build a tiny house?

A tiny house built first and permitted later can end up with no legal place to stand. The rules, routes and real examples are on the tiny house permit page, and the reasons projects get refused are on why tiny house permits get rejected.

Tiny houses fall outside the All-in offer, so we quote them individually: send your address and plans, and the quote shows your city's rules and published fees before you commit.

Common questions

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Sources

1. City of Boise, Idaho, Planning and Development Services, Tiny Houses. Checked October 13, 2026.
2. City of Seattle, 2021 Seattle Residential Code, Appendix AQ, Tiny Houses (with Washington amendments). Checked October 13, 2026.
3. City of Albion, Idaho, Ordinance No. 2025-06-01, Tiny House Regulations (passed June 3, 2025). Checked October 13, 2026.
4. Colorado Department of Local Affairs, Division of Housing, Tiny Homes and Tiny Houses Information Center. Checked October 13, 2026.

Keep reading

• Tiny house permits, explainedDo you need a permit for a tiny house? How the code's tiny house appendix works, why wheels change everything, and what zoning, utilities and inspections require.
• Why tiny house permits get rejectedWhy tiny house projects are refused: zoning that does not allow them, wheels that make them RVs, no foundation or utilities, lofts and egress that fail the code.
• ADU permits, explainedWhat an ADU permit involves: whether your lot qualifies, the plans cities ask for, impact and utility fees, review times and renting rules, from official city pages.
• Owner-builder permits, explainedWhat an owner-builder permit is, who can get one, the Florida and California rules on selling within a year, liability for workers, and what you sign at the counter.
• Permit Quote for ADUs, Garage Conversions and Tiny Houses
• Garage conversion permits, explainedDo you need a permit to convert a garage into living space? Yes. What cities require: drawings, energy code, egress, ceiling height, heat, parking and real fees.
• Barndominium permits, explainedDo you need a permit to build a barndominium? Why it is permitted as a house, when an engineer must stamp the plans, septic and floodplain permits, and real fees.