What is the 108 square foot rule in BC?

The 108 square foot rule refers to the BC Building Code exemption for accessory structures at or under 10 m² (107.6 sq ft, commonly rounded to 108 sq ft). Structures meeting this size limit -- along with other conditions -- do not require a building permit. This applies to greenhouses, garden sheds, workshops, playhouses, and other detached single-storey accessory buildings.

Where does the 108 square foot rule come from?

The exemption comes from the BC Building Code (adopted under the Building Act). The code states that building permits are not required for accessory buildings with a building area not exceeding 10 m². Since 10 m² equals 107.6 square feet, this is commonly referred to as the 108 square foot rule.

What structures does the 108 sq ft exemption cover?

The exemption covers any detached single-storey accessory structure under 10 m² that is not used for sleeping or dwelling. Common examples: greenhouses, garden sheds, tool sheds, small workshops, chicken coops, firewood shelters, pump houses, playhouses, and covered garden structures. The structure must be detached from the principal building.

Does the 108 sq ft rule exempt me from zoning bylaws?

No. The permit exemption only applies to the building permit requirement under the building code. You must still comply with municipal zoning bylaws including setbacks from property lines, lot coverage maximums, height limits, and use restrictions. Zoning is separate from building code -- the exemption does not override it.

Is there a height limit for the 108 sq ft exemption?

The BC Building Code requires the structure be single storey. Municipal zoning bylaws typically limit accessory structure height to 3.5 to 4.5 metres (approximately 11.5 to 15 feet) to the peak. A standard greenhouse with a 9-foot south wall and 7-foot north wall sits well under these limits.

Can I build multiple 108 sq ft structures without permits?

The BC Building Code does not limit the number of permit-exempt structures per property. However, municipal zoning bylaws often limit total lot coverage (all structures combined, typically 35-50% of lot area) and some cap the number or total area of accessory buildings. You cannot build two 108 sq ft structures adjacent to each other and call it one building -- that would be treated as a single 216 sq ft structure requiring a permit.

Does the 108 sq ft rule apply everywhere in BC?

The BC Building Code applies province-wide, so the 10 m² exemption is the baseline everywhere. However, municipalities can adopt stricter requirements. Some require notification for all structures, some have lower size thresholds, and some require permits for any structure regardless of size. Always confirm with your local building department.

What does the 108 sq ft rule NOT exempt?

The exemption does not cover: zoning bylaw compliance (setbacks, lot coverage, height), electrical work (separate electrical permit still needed), plumbing (separate plumbing permit needed), structures attached to the principal building, structures used for dwelling or sleeping, multi-storey structures, or structures on land with specific covenants or easements restricting development.

108 Square Foot Rule BC: Build Without a Permit

If you want to build a small structure on your property in BC -- a greenhouse, garden shed, workshop, chicken coop, or storage building -- you have probably heard that you do not need a building permit if it is under 108 square feet. That is mostly correct. But there are conditions, limitations, and things this rule does NOT exempt you from that trip people up. This guide covers the full picture.

What the Rule Actually Says

The BC Building Code exempts accessory structures from building permit requirements when the building area does not exceed 10 square metres. In imperial units, 10 m² equals 107.6 square feet -- commonly rounded up to 108 square feet.

The code does not use the phrase "108 square foot rule" -- that is a colloquial name. The actual provision refers to "accessory buildings with a building area not exceeding 10 m²" as exempt from the requirement to obtain a building permit.

Conditions for the Exemption

The structure must meet ALL of the following to qualify:

Building area at or under 10 m² (108 sq ft): Measured to the outer edge of the walls at floor level.
Single storey: No lofts, mezzanines, or second floors.
Accessory use: Secondary to the principal building on the lot (your house). Cannot be the primary structure.
Detached: Physically separate from the principal building. Not attached to the house.
Not for dwelling or sleeping: Cannot be used as living space, a bedroom, a rental suite, or a habitable room.
No plumbing fixtures requiring drainage: No sinks, toilets, or floor drains connected to the sanitary sewer.

If any of these conditions is not met, a building permit is required regardless of size.

Where Does the Rule Come From?

The exemption is established in the BC Building Code, which is adopted under the provincial Building Act. The Building Act gives municipalities the authority to require building permits, and the BC Building Code sets out when permits are and are not required.

The 10 m² threshold has been in the code for decades. It exists because small, simple structures pose minimal risk to public safety -- they do not have complex structural systems, they do not house people overnight, and their failure does not endanger adjacent properties.

The threshold is consistent across Canada (the National Building Code uses the same 10 m² figure), though provinces and municipalities can set lower thresholds if they choose.

What Structures Does It Cover?

Any detached, single-storey accessory building under 10 m² that is not used for dwelling. Common examples:

Greenhouses
Garden sheds
Tool storage sheds
Small workshops
Chicken coops
Firewood shelters
Pump houses / well houses
Playhouses
Covered garden structures (pergolas with roof)
Hot tub enclosures (no plumbing in the structure itself)
Storage buildings

The use does not matter as long as it is accessory, not dwelling, and meets the size and other conditions.

How Building Area Is Measured

Building area is measured to the outside face of the exterior walls at floor level. It does NOT include:

Roof overhangs (unless enclosed)
Unenclosed porches or decks
Foundation extending beyond the walls

It DOES include:

The full enclosed floor area within the walls
Any attached enclosed porch or vestibule (this counts toward the 10 m²)

For a rectangular greenhouse: width x length measured to the outside of the framing. A 9-foot by 12-foot greenhouse (outside dimensions) = 108 square feet = exactly 10.03 m². That is right at the threshold. Technically, you want to be at or under 10.0 m². Some builders frame at 8'11" x 11'11" to ensure they stay under with certainty.

Height Limits

The BC Building Code requires the structure to be single storey for the exemption to apply. It does not specify an exact height limit -- that comes from your municipal zoning bylaw.

Typical height limits for accessory structures in Vancouver Island municipalities:

Municipality / District	Max Height (Accessory)
Campbell River	4.5 m (14.8 ft) to peak
Courtenay	4.5 m (14.8 ft) to peak
Nanaimo	4.5 m (14.8 ft) to peak
Comox Valley RD	4.5 m (14.8 ft) to peak
Strathcona RD	4.5 m (14.8 ft) to peak
Capital RD (some areas)	3.5 m (11.5 ft) to peak

Our 9x12 greenhouse has a south wall at 9 feet (2.7 m) and a north wall at 7 feet (2.1 m). The peak height from grade is approximately 3 metres -- well under any municipal height limit for accessory structures.

Setback Requirements Still Apply

This is where people get confused. The permit exemption only removes the requirement for a building permit. It does NOT exempt you from zoning bylaws. You still must comply with:

Property line setbacks: Typically 1.5 metres from rear and side property lines for accessory structures. Check your specific zone.
Lot coverage maximums: The greenhouse footprint counts toward your total lot coverage (all buildings combined). Typical residential maximums are 35 to 50 percent.
Use restrictions: The structure's use must be permitted in your zoning designation.
Easements: Cannot build in a registered easement (utility, drainage, access). Check your title.
Flood construction levels: If your property has a flood construction level, even small structures may need to be above it.

Violating zoning bylaws -- even with a permit-exempt structure -- can result in enforcement action from your municipality. They can order removal or modification regardless of whether a building permit was required.

What the Exemption Does NOT Cover

This is the critical section. The 108 sq ft rule exempts you from a BUILDING PERMIT only. It does not exempt you from:

Requirement	Still Applies?	Notes
Zoning bylaw compliance	Yes	Setbacks, lot coverage, height, use
Electrical permit	Yes	Any electrical wiring requires separate electrical permit
Plumbing permit	Yes	Any plumbing fixtures require separate plumbing permit
ALR regulations	Yes	Though greenhouses are permitted farm use on ALR land
Strata bylaws	Yes	Strata properties have their own rules on outbuildings
Heritage designation	Yes	Heritage properties may restrict all construction
Wildfire interface requirements	Yes	FireSmart requirements may apply to materials and placement
Covenant restrictions	Yes	Check your title -- some covenants restrict outbuildings
Environmental setbacks (riparian)	Yes	Riparian Areas Protection Act applies regardless

Municipal Variations

The 10 m² exemption is the provincial standard. Municipalities can be stricter. Here are real variations I have encountered on Vancouver Island:

Notification Requirements

Some municipalities require you to submit a brief notification form even for permit-exempt structures. This is not a permit application -- no fee, no review, no inspection. They just want a record of what is being built and where. This takes 10 minutes and keeps you in good standing.

Total Accessory Area Caps

Some zoning bylaws limit the total combined area of all accessory structures on a lot (e.g., 50 m² maximum total). If you already have a 40 m² garage, you may only have 10 m² of allowance left for additional structures -- regardless of the permit exemption.

Lot Size Minimums

Some zones only permit accessory structures on lots above a certain size. Urban lots under 500 m² may have restrictions that rural lots do not.

Appearance and Materials

Some municipalities in design-controlled zones have requirements for the appearance of outbuildings -- materials, colours, or roofing that must match or complement the principal building. This is uncommon for rural properties but exists in some urban residential zones.

Multiple Structures: Can You Build More Than One?

The BC Building Code does not limit the number of permit-exempt accessory structures per lot. In theory, you could build three separate 108 sq ft structures without a permit.

However:

Municipal lot coverage maximums still apply -- all structures combined cannot exceed the allowed percentage.
Some zoning bylaws cap the number or total area of accessory buildings explicitly.
You cannot build two structures immediately adjacent to each other and call them separate buildings. If there is no meaningful separation (shared wall, zero gap), the municipality will treat them as one larger structure requiring a permit.
Each structure must independently meet all exemption criteria (detached, single storey, no dwelling, etc.).

Practical Applications

Greenhouses

A 9x12 foot (108 sq ft) greenhouse is the maximum size you can build without a permit in most BC municipalities. Our 9x12 backyard greenhouse is specifically designed around this threshold -- passive solar, shed-roof, sono tube foundation, no electrical required for basic operation.

Want to know whether your greenhouse project needs a permit? See: Do You Need a Building Permit for a Greenhouse in BC?

Garden Sheds

A standard garden shed at 8x10 (80 sq ft) or 8x12 (96 sq ft) falls well under the threshold. A 10x12 (120 sq ft) shed exceeds it and requires a permit. Many prefab shed companies sell at 10x10 (100 sq ft) -- that works.

Workshops

108 square feet is tight for a workshop. You can fit a small workbench, some wall-mounted tool storage, and enough floor space to work on one project at a time. If you need electrical power (likely for a workshop), remember that the electrical permit is separate -- you need it, but it does not trigger a building permit.

Chicken Coops

Most backyard chicken coops are well under 108 sq ft. A coop for 6 to 12 birds rarely exceeds 40 to 60 sq ft. Permit-exempt without question, though check your municipal animal bylaw for the number of chickens allowed.

How Swell Farms Uses the 108 Sq Ft Threshold

We designed our backyard greenhouse specifically at 9 feet by 12 feet (108 sq ft) because:

It is the maximum floor area that avoids the permit process
It is enough space for a 1-2 person household to grow year-round greens, herbs, and season-extended tomatoes
The shed-roof design fits under any municipal height limit for accessory structures
No plumbing or electrical is required for basic passive solar operation (manual vents, hand-watering)
Sono tube pier foundation does not require excavation inspection
It can be built and producing food within days of delivery, not weeks of permit waiting

For people who need more growing space, our 14x20 production unit (280 sq ft) requires a permit -- and we handle the permit drawings and research as part of the project scope. But for the homeowner who wants to start growing without bureaucratic overhead, the 9x12 is purpose-built for that.

Step-by-Step: Building a Permit-Exempt Structure

Confirm zoning: Look up your property's zoning designation on your municipality's website or call the planning department.
Check setbacks: Determine minimum distances from property lines for accessory structures in your zone.
Check lot coverage: Add up all existing building footprints on your lot. Confirm the new structure will not push total coverage over the maximum.
Check easements: Review your title for registered easements. Do not build in them.
Check for municipal notification requirements: Some municipalities want a brief form submitted. Takes 10 minutes.
Design and size: Keep building area at or under 10 m² (108 sq ft). Single storey. Detached.
Build: No permit required. No inspections. No waiting period.
If adding electrical: Apply for a separate electrical permit through your municipality or directly with BC Safety Authority (Technical Safety BC). A licensed electrician must do or supervise the work.

Common Questions Answered

Do roof overhangs count toward the 108 sq ft?

No. Building area is measured to the outside face of the exterior walls at floor level. Roof overhangs that are not enclosed do not count.

Does a concrete pad count as part of the building area?

No. The building area is the enclosed structure above the foundation. A concrete pad that extends beyond the walls is not included.

Can I add a covered porch to a 108 sq ft structure?

If the porch is enclosed (walls and roof), it counts toward building area. If it is open (roof only, no walls), most municipalities do not count it. Check locally -- interpretations vary.

What about a loft for storage?

A loft makes the structure multi-storey. The exemption requires single storey. Adding a storage loft means you need a building permit.

Can I pour a concrete foundation without a permit?

For a permit-exempt structure, yes. The foundation is part of the exempt building. However, if you are pouring a full perimeter foundation and your municipality has a "foundation inspection" requirement for all concrete work, check first. Sono tube piers avoid this entirely.

Sources

BC Building Code -- Building Act, accessory structure provisions
Building Act (SBC 2015, c.2) -- Province of British Columbia
Municipal zoning bylaws -- Campbell River, Courtenay, Nanaimo, Comox Valley RD, Strathcona RD

Reid Graham

Owner / Operator, Swell Farms. 10 years of earthworks experience on Vancouver Island. Based on Quadra Island, BC.

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