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Code guide

Tiny Houses and the Ontario Building Code

Tiny homes under the 2024 Ontario Building Code: when they are buildings, the 13.5 m² combined-space minimum, ceiling heights, factory-built CSA rules and permits.
combined living space for up to two persons
13.5 m²
combined living space for up to two persons
size where a structure becomes a building
10 m²
size where a structure becomes a building
ceiling over 75% of living areas
2,300 mm
ceiling over 75% of living areas
maximum section width under CSA Z240
4.88 m
maximum section width under CSA Z240

Last updated

The Ontario Building Code has no minimum size for a house, but a year-round dwelling must meet minimum room areas: where living, dining, bedroom and kitchen spaces are combined for not more than two persons, the combined area must be at least 13.5 m² (OBC Div. B 9.5.3E.1.OBC Div. B 9.5.3E.1. Combined Living, Dining, Bedroom and Kitchen Spaces(1) Despite Subsections 9.5.3A. to 9.5.3D.., where living, dining, bedroom and kitchen spaces are combined in a dwelling unit that contains sleeping accommodation for not more than two persons, the area of the combined spaces shall be not less than 13.5 m² .), and rooms can be smaller if built-in furniture shows they still work (9.5.1.3.OBC Div. B 9.5.1.3. Lesser Areas and Dimensions(1) Areas of rooms and spaces are permitted to be less than required in this Section provided it can be shown that the rooms and spaces are adequate for their intended use, such as by the provision of built-in furniture to compensate for reduced sizes.). A tiny home over 10 m², or with plumbing, is a "building" that needs a permit (BCA s. 1, buildingBCA s. 1 building“building” means, (a) a structure occupying an area greater than ten square metres consisting of a wall, roof and floor or any of them or a structural system serving the function thereof including all plumbing, works, fixtures and service systems appurtenant thereto, (b) a structure occupying an area of ten square…).

This page explains how the Building Code applies to tiny homes, from room sizes to factory-built units. Zoning decides whether and where a tiny home can be placed on a lot, and that is set by your municipality, so check both before you build or buy.

Tiny house rules at a glance

Item Rule in short Where to look
Is it a building? over 10 m², or any size with plumbing BCA s. 1, building
Permit needed to construct a building BCA s. 8
Shed exemption storage only, 15 m² or less, no plumbing Div. C 1.3.1.1.(6)
Room size rules apply to year-round principal residences 9.5.1.0A.
Combined living space, up to 2 persons 13.5 m² 9.5.3E.1.
Smaller rooms allowed if shown adequate, such as with built-ins 9.5.1.3.
Ceiling heights Table 9.5.3.1. 9.5.3.1.
Fixtures kitchen sink, lavatory, tub or shower, toilet where water is available 9.31.4.1.
Factory-built CSA Z240.2.1 or CSA A277, plus site rules 9.1.1.9.
Seasonal cabins Section 9.37 applies 9.37.1.1.

This is our summary of the Act and the code, not a copy of them.

When a tiny home is a building

The Building Code Act defines a building to include a structure occupying more than 10 m² with a wall, roof and floor or any of them, and any structure of 10 m² or less that contains plumbing (BCA s. 1, buildingBCA s. 1 building“building” means, (a) a structure occupying an area greater than ten square metres consisting of a wall, roof and floor or any of them or a structural system serving the function thereof including all plumbing, works, fixtures and service systems appurtenant thereto, (b) a structure occupying an area of ten square…). Constructing a building needs a permit (BCA s. 8BCA s. 8 Building permits(1) No person shall construct or demolish a building or cause a building to be constructed or demolished unless a permit has been issued therefor by the chief building official. (1.1) An application for a permit to construct or demolish a building may be made by a person specified by regulation and the prescribed form…), so almost every tiny home people live in is a building.

The permit exemption for small sheds is narrow: 15 m² or less, one storey, detached, used only for storage, and no plumbing (Div. C 1.3.1.1.(6)OBC Div. C 1.3.1.1. Requirement for Permits(1) A person is exempt from the requirement to obtain a permit under section 8 of the Act, (a) for the demolition of a farm building located on a farm, (b) subject to Sentence (2), for the construction or demolition of a building in territory without municipal organization, or (c) for the construction of a Class 1…). A shed converted into a place to sleep no longer fits it. See our building permit guide.

Minimum room sizes

The room size rules in Section 9.5 apply to dwelling units intended for use on a continuing or year-round basis as the principal residence (9.5.1.0A.OBC Div. B 9.5.1.0A. Application(1) Except as otherwise specified in this Part, this Section applies only to dwelling units that are intended for use on a continuing or year-round basis as the principal residence of the occupant.). For a small home, the key numbers are:

  • Everything combined. Where living, dining, bedroom and kitchen spaces are combined in a dwelling unit with sleeping accommodation for not more than two persons, the combined area must be at least 13.5 m² (9.5.3E.1.OBC Div. B 9.5.3E.1. Combined Living, Dining, Bedroom and Kitchen Spaces(1) Despite Subsections 9.5.3A. to 9.5.3D.., where living, dining, bedroom and kitchen spaces are combined in a dwelling unit that contains sleeping accommodation for not more than two persons, the area of the combined spaces shall be not less than 13.5 m² .).
  • Kitchen. At least 4.2 m², or 3.7 m² where the unit sleeps not more than two (9.5.3C.1.OBC Div. B 9.5.3C.1. Kitchen Areas(1) Kitchen areas within dwelling units either separate from or in combination with other spaces, shall have an area of not less than 4.2 m² including the area occupied by the base cabinets, except that in dwelling units containing sleeping accommodation for not more than two persons, the minimum area shall be 3.7 m².).
  • Living area. 13.5 m² normally, or 11 m² when combined with kitchen and dining in a unit for not more than two (9.5.3A.1.OBC Div. B 9.5.3A.1. Areas of Living Rooms and Spaces(1) Living areas within dwelling units, either as separate rooms or in combination with other spaces, shall have an area not less than 13.5 m². (2) Where the area of a living space is combined with a kitchen and dining area, the living area alone in a dwelling unit that contains sleeping accommodation for not more…).
  • Bedroom. A separate bedroom needs 7 m² (9.8 m² for the main bedroom), and a bedroom space combined with other space needs 4.2 m² (9.5.3D.1. to 9.5.3D.3.OBC Div. B 9.5.3D.3. Areas of Combination Bedrooms(1) Bedroom spaces in combination with other spaces in dwelling units shall have an area not less than 4.2 m².).

Room areas are measured between finished wall surfaces (9.5.1.1.OBC Div. B 9.5.1.1. Method of Measurement(1) Except as otherwise specified in this Part, the areas, dimensions and heights of rooms or spaces shall be measured between finished wall surfaces and between finished floor and ceiling surfaces.). Rooms may be smaller than these minimums where it can be shown they are adequate for their use, such as by built-in furniture that compensates for the reduced size (9.5.1.3.OBC Div. B 9.5.1.3. Lesser Areas and Dimensions(1) Areas of rooms and spaces are permitted to be less than required in this Section provided it can be shown that the rooms and spaces are adequate for their intended use, such as by the provision of built-in furniture to compensate for reduced sizes.). Murphy beds, built-in benches and storage stairs are the usual ways tiny homes make that case.

Ceilings, lofts and stairs

Living areas and kitchens need a ceiling of 2,300 mm over at least 75% of the required area, and bedroom spaces 2,300 mm over half their area or 2,100 mm over all of it (Table 9.5.3.1.OBC Div. B Table 9.5.3.1. Room Ceiling Heights — Forming Part of Sentences 9.5.3.1.(1) and (4)Table 9.5.3.1 — Room Ceiling Heights — Forming Part of Sentences 9.5.3.1.(1) and (4) Room or Space | Minimum Heights[1] Living room or space, dining room or space, kitchen or kitchen space | 2,300 mm over at least 75% of the required floor area with a clear height of 2,100 mm at any point over the required area…). A sleeping loft that counts as a bedroom space must meet the bedroom heights, and the loft needs a stair that meets the stair rules or an approved alternative. See ceiling heights and room sizes and stairs.

Safety basics still apply

A tiny home is still a dwelling unit, so the usual Part 9 safety rules apply:

  • Smoke and CO alarms, hard-wired and interconnected. See smoke and CO alarms.
  • A bedroom egress window where sleeping areas lack a door to the outside. See bedroom egress windows.
  • Plumbing fixtures: a kitchen sink, lavatory, bathtub or shower, and water closet where a water distribution system is available (9.31.4.1.OBC Div. B 9.31.4.1. Required Fixtures(1) A kitchen sink, lavatory, bathtub or shower, and water closet shall be provided for every dwelling unit where a water distribution system is available.).
  • Insulation and ventilation to SB-12 and Section 9.32.

Factory-built tiny homes

A manufactured building is deemed to comply with the code if it is designed and built to CSA Z240.2.1 (in sections not wider than 4.88 m) or certified under CSA A277 (9.1.1.9.(1)OBC Div. B 9.1.1.9. Site Assembled and Factory-Built Buildings(1) Except as provided in Sentence (2) and in Sentence 12.2.1.2.(2), a manufactured building is deemed to comply with this Code if it is designed and constructed in compliance with, (a) CSA Z240.2.1, "Structural requirements for manufactured homes," if the building is constructed in sections not wider than 4.88 m, or…). The code still applies to anything built outside the factory and to the site installation, including the foundation and service connections (9.1.1.9.(2)OBC Div. B 9.1.1.9. Site Assembled and Factory-Built Buildings(1) Except as provided in Sentence (2) and in Sentence 12.2.1.2.(2), a manufactured building is deemed to comply with this Code if it is designed and constructed in compliance with, (a) CSA Z240.2.1, "Structural requirements for manufactured homes," if the building is constructed in sections not wider than 4.88 m, or…). Buildings that are not masonry and whose superstructure passes the CSA Z240.2.1 deformation resistance test are exempt from the usual foundation depth table (9.12.2.2.(6)OBC Div. B 9.12.2.2. Minimum Depth of Foundations(1) Except as provided in Sentences (4) to (7), the minimum depth of foundations below finished ground level shall conform to Table 9.12.2.2. (2) Where a foundation is insulated in a manner that will reduce the heat flow to the soil beneath the footings, the foundation depth shall conform to that required for…).

Seasonal cabins and wheels

The room size rules apply only to year-round principal residences (9.5.1.0A.OBC Div. B 9.5.1.0A. Application(1) Except as otherwise specified in this Part, this Section applies only to dwelling units that are intended for use on a continuing or year-round basis as the principal residence of the occupant.). Seasonal recreational buildings follow Section 9.37, which applies the rest of Part 9 with specific exemptions (9.37.1.1.OBC Div. B 9.37.1.1. Application(1) This Section applies to buildings of residential occupancy used or intended to be used as seasonal recreational buildings. (2) The buildings described in Sentence (1) shall comply with all the requirements of this Part, except where they are specifically exempted in this Section.).

A tiny home on wheels is a grey area. Whether it is treated as a vehicle or a building depends on how it is used and installed, and municipalities decide it case by case. Zoning also limits where you can live in one. Ask your municipality before you buy.

Common mistakes

  1. Relying on the shed exemption. It covers storage only, 15 m² or less, with no plumbing.
  2. Assuming there is a minimum house size. The limits are on rooms and combined spaces, not the whole house.
  3. Skipping zoning. The Building Code does not decide where a tiny home can go.
  4. Lofts with ladders that do not meet the stair or egress rules.
  5. Forgetting the site work for factory-built units: foundations and services still need a permit.

How to look it up yourself

Open Division B, Part 9 of the 2024 Compendium. Section 9.5 covers room sizes. Search terms that appear in the code text:

  • "Combined Living, Dining, Bedroom and Kitchen Spaces" (9.5.3E.1.)
  • "Lesser Areas and Dimensions" (9.5.1.3.)
  • "Site Assembled and Factory-Built Buildings" (9.1.1.9.)

Read the article in the code viewer alongside the building definition in the Act.

BCIN exam angle

Room area minimums, the combined-space rule and the definition of a building are tested on the House and General Legal/Process exams. Study the House chapter on rooms, spaces, glass, windows and doors, then try the free quiz on the House exam page.

Based on the official 2024 Building Code Compendium on ontario.ca.

© King's Printer for Ontario, 2024. Reproduced with permission.

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Frequently asked questions

Is there a minimum house size in the Ontario Building Code?
There is no minimum size for a whole house, but there are minimum room areas for a year-round dwelling. Where living, dining, bedroom and kitchen spaces are combined in a dwelling unit with sleeping accommodation for not more than two persons, the combined area must be at least 13.5 m² (Division B, Article 9.5.3E.1.).
Do I need a building permit for a tiny house in Ontario?
Usually yes. Under the Building Code Act, a structure over 10 m², or any structure with plumbing, is a building, and constructing a building needs a permit. The shed exemption covers only storage buildings of 15 m² or less with no plumbing, so it never covers a tiny home someone lives in.
Can rooms in a tiny house be smaller than the code minimums?
Yes, if it can be shown the rooms are adequate for their intended use, such as with built-in furniture that makes up for the smaller size (Division B, Article 9.5.1.3.). Your building department decides whether the design shows that.
Are factory-built tiny homes allowed in Ontario?
Yes. A manufactured building is deemed to comply with the Building Code if it is built to CSA Z240.2.1 (in sections not wider than 4.88 m) or certified under CSA A277. The code still applies to its foundation and site installation (Division B, Article 9.1.1.9.).
Is a tiny home on wheels a building?
It depends on how it is used and installed. Placed on a lot and used as a home, it may be treated as a building, and zoning decides where you may live in one. Ask your municipality before you buy or build.