A secondary suite in the City of Duncan needs a City building permit, Technical Safety BC electrical work by a licensed contractor, and an occupancy permit before anyone moves in. Here’s how to confirm the City is your building authority, the current zoning and parking rules, the flood construction level, fees, the BC Building Code 2024 suite rules and each inspection, with two short videos.
City of Duncan only. This page covers the City of Duncan. Many Duncan mailing addresses are actually in the District of North Cowichan or the Cowichan Valley Regional District (CVRD), which have their own building departments and suite rules, and the City’s maps page also lists Cowichan Tribes as a separate jurisdiction. Check the City’s street and zoning maps first: Do I live in the City of Duncan?. Still unsure? Call City of Duncan Development Services at 250-746-6126 or email developmentservices@duncan.ca.
This guide covers adding a secondary suite to a house in the City of Duncan, or legalizing one built without a permit. The City allows suites under Zoning Bylaw No. 3166, issues building and plumbing permits under Building Bylaw No. 3254, 2026, and charges fees under Fees and Charges Bylaw No. 3212. Electrical and gas permits come from Technical Safety BC. Construction follows the BC Building Code 2024, which has a table of alternate methods for adding a suite to an existing house. Every figure below was checked on September 30, 2026 against the City’s pages, bylaws and suite documents and the BC Building Code, listed under Sources.
General information only. tradeschoolsandpermitinfo.ca is an independent site, not the City of Duncan. This page is not legal or building-code advice, and your building official has the final say. Confirm the rules for your address with the City before you design or build.
Duncan Secondary Suite Permit: Jurisdiction, Zoning, Flood Rules, Fees & Inspections (2026)
A step-by-step walkthrough of getting a secondary suite approved in the City of Duncan (not North Cowichan or the CVRD), checked against Zoning Bylaw 3166, Building Bylaw No. 3254, the Flood Plain Management Bylaw and the Fees and Charges Bylaw. Planning a basement, in-house or detached suite in Duncan? First make sure the City of Duncan is your building authority: many Duncan mailing addresses are in North Cowichan or the Cowichan Valley Regional District, which have their own rules. This walkthrough covers City of Duncan rules only: what counts as a suite, zoning and parking under Zoning Bylaw 3166, the flood construction level, the permits you need (City and Technical Safety BC), plans, applying, fees with a worked example, inspections, and occupancy.
Download the video (MP4) · Watch on YouTube (BC Trades & Permits)
Narration uses a synthetic (AI-generated) voice.
Is my project allowed? Zoning decides setbacks, height, lot coverage and whether a suite is allowed on your lot. Check it before you draw or apply for the permit: look up your address on the map, then read your zone in the bylaw.
Checked October 26, 2026 (City of Duncan): zoning and addressing map (PDF) · Zoning Bylaw No. 3166 (consolidated, PDF)
From Zoning Bylaw No. 3166, consolidated with amendments to August 24, 2026 (bylaw; zoning map):
The City’s older sheet doesn’t match the bylaw. The City still links a 2018 Secondary Suite Regulations sheet that says an attached suite can be no larger than 40% of the dwelling’s floor area or 90 m², that detached suites need a minimum 600 m² lot, and that a suite needs one extra parking space plus two for the principal dwelling (2018 sheet, PDF). We found no 40% limit, no 600 m² detached-suite lot rule and no such parking numbers in the current bylaw; 600 m² appears as the LDR minimum parcel area for subdivision (s.4.4.1). The City’s Secondary Suites page (July 24, 2025) also still says detached suites need the minimum lot size. We follow the bylaw. Confirm with Development Services before you design.
For legalizing a suite, the City’s Secondary Suites Policy (2013) asks for a building permit application with two sets of drawings (source):
Building Bylaw 3254 s.8.2 requires paper and electronic PDF, including two full-sized sets of drawings (36 by 48 inches), unless a building official allows smaller sets or an electronic-only submission. The City also posts a Secondary Suite Example Plan, dated 2013-APR-25 (Example Plan, PDF). It predates the current code (it shows ionization smoke alarms and the old 40% size rule), so use it only as an illustration.
From the Fees and Charges Bylaw No. 3212, consolidated to August 24, 2026 (Bylaw 3212; City fee sheet, PDF):
| Item | Bylaw 3212 |
|---|---|
| Plan review (per submission, at application) | $50 up to $25,000 of value; $100 over $25,000 to $50,000; $200 over $50,000 to $100,000; $200 plus $1.25 per $1,000 over $100,000 |
| Building permit | $50 minimum; $8 per $1,000 of value up to $100,000; $800 plus $5 per $1,000 over $100,000 |
| Construction without a permit | Double the building permit fee |
| Plumbing permit | $12 per fixture; $24 minimum |
| Secondary suite inspection | $100 |
| Callback inspection | $50 |
| Removal of notice on title | $300 per title |
The City’s application form says that if multiple plan checks are needed, only the first is credited toward the building permit fee, and the City keeps the fees if the project doesn’t proceed (source). The plan review and building permit fees are waived for detached suites built from the City’s pre-approved template plans without alterations.
Our own arithmetic, not a City quote: $60,000 of work would carry a building permit fee of 60 × $8 = $480. The plan review fee at that value is $200, paid at application and, per the form, credited toward the permit fee, leaving $280 at issuance by our reading. Add plumbing ($12 per fixture) and the $100 suite inspection fee.
Development cost charges: DCC Bylaw No. 3234, 2023 imposes charges on building permits that authorize the construction, alteration or extension of a building (s.4.1), including buildings with fewer than four self-contained dwelling units (s.4.3). Its Schedule A has no secondary suite category; for an unlisted type, the Director of Public Works and Engineering decides which listed type imposes the most similar cost burden (s.4.4; Bylaw 3234). Ask the City whether a charge applies to your suite.
Utilities: Bylaw 3212 sets higher annual sewer rent and water rates for a single family residence with a suite than for one without. The City has a policy on exemptions from the extra utility charges, for example when the suite is removed, taken off the rental market for a year or occupied by a family member (source).
Building a Secondary Suite in Duncan, BC: Fire Separation, Exits, Alarms & Headroom (2026)
What the BC Building Code 2024 and City of Duncan suite documents ask for when an existing house in the City gets a secondary suite, including the code table of alternate methods for existing houses. Turning part of an existing house in the City of Duncan into a secondary suite? (In North Cowichan or the CVRD? Check with them: different building authority.) This walkthrough covers the BC Building Code 2024 construction rules and the City’s own suite documents: when the code’s alternate methods for existing houses can be used, how the fire separation rating depends on your smoke alarms (15, 30 or 45 minutes), wall and floor assemblies, doors, heating, ventilation and plumbing through the separation, bedroom egress windows and shared exits, smoke and CO alarms, ceiling heights, sound separation, electrical and gas permits from Technical Safety BC, and inspections through to the occupancy permit.
Download the video (MP4) · Watch on YouTube (BC Trades & Permits)
Narration uses a synthetic (AI-generated) voice.
A secondary suite is built to Part 9 of the BC Building Code. For alterations to an existing building to add a secondary suite (not new additions or new buildings), the code lets you substitute the alternate compliance methods in Division A Table 1.1.1.1.(6) (Sentence 1.1.1.1.(6)). The code’s note says the table isn’t intended to be applied as a retroactive code, nor to new construction (Note A-1.1.1.1.(6)), and an alteration must not decrease the existing level of life safety and building performance (1.1.1.2.(1)). Duncan’s Building Bylaw adds that the entire building must comply under the code’s provisions for existing buildings (s.5.4). These are summaries, not the code wording; your approved plans and inspector have the final say (BC Building Code 2024).
| Topic | Code requirement (Division B unless noted) | Existing house: Table 1.1.1.1.(6) alternative |
|---|---|---|
| Fire separation between the units and any common spaces | 9.10.9.16.(4): 15 min when all smoke alarms in the house are photo-electric and interconnected (9.10.19.5.(2)(a)); 30 min when an additional photo-electric smoke alarm is installed in each dwelling unit and common space and interconnected (9.10.19.5.(2)(b)); 45 min when neither is done; no rating required if the building is sprinklered. | — |
| 15 min assembly | 9.10.3.1.(2) permits the 9.11.1.1.(2)(a) construction: joist spaces filled with at least 150 mm nominal sound-absorbing material, stud spaces filled, resilient channel on one side at 400 or 600 mm o.c., and at least 12.7 mm gypsum board on ceilings and both sides of walls. | — |
| 30 min assembly | 9.10.3.1.(3): wood studs, joist and stud spaces filled with the listed insulation, resilient channel on one side at 400 or 600 mm o.c., and at least 12.7 mm gypsum board on ceilings and both sides of walls. The City’s Secondary Suite Example Plan (updated 2013-APR-25) shows a 30 min rating with minimum 1/2″ regular drywall on both sides of walls and 5/8″ Type X on ceilings. It predates the BC Building Code 2024, so confirm your assembly with the City (Example Plan, 2013, PDF). | Item 7: add resilient metal channel at 400 or 600 mm o.c. and another layer of at least 12.7 mm gypsum board to one side of an existing finished wall with at least 12.7 mm gypsum board on each side, or of an existing floor-ceiling with at least 12.7 mm gypsum on the ceiling side. |
| Supporting elements | 9.10.8.3.(1): loadbearing walls, columns and arches carry the rating of the floor they support. | Item 8: light-frame walls, columns, arches and beams and loadbearing steel supporting floors between the units (and common spaces) protected by at least 12.7 mm gypsum board; heavy timber, masonry and concrete excepted. |
| Doors in the fire separation | Every swing door needs a latch (9.10.13.9.) and a self-closing device (9.10.13.10.). A 30 or 45 min separation needs a 20 min closure (Table 9.10.13.1.); a 45 mm solid core wood door conforming to CAN/ULC-S113 is permitted, with no more than 6 mm clearance beneath and 3 mm at the sides and top (9.10.13.2.), in a wood frame at least 38 mm thick if the frame isn’t tested and rated (9.10.13.3.). | — |
| Heating and ventilation | The City’s Example Plan (2013) says air cannot be circulated between dwelling units and the suite must have its own separate heating system. It’s an older document, so confirm with the City before you plan a shared system (source). A system serving more than one dwelling unit is designed to prevent smoke circulation on a signal from a duct-type smoke detector. 9.10.9.9.(6): ducts through fire separations need no fire dampers if noncombustible with all openings in the duct system serving only one fire compartment. 9.33.4.3.(1): where a single heating system serves a house with a secondary suite, each dwelling unit gets its own temperature control. | — |
| Plumbing through the separation | 9.10.9.7.: combustible drain, waste and vent piping through a rated fire separation is sealed by a firestop with an F rating not less than the separation’s required rating (9.10.9.6.(1)(a)). | — |
| Bedroom egress | 9.9.10.1.: unless the suite is sprinklered, each bedroom has an outside window or exterior door openable from inside without keys, tools or special knowledge; a window gives an unobstructed opening of at least 0.35 m² with no dimension under 380 mm; 760 mm clearance in a window well; a well cover openable from inside. | — |
| Shared exit, single stair | 9.9.9.3.(3): where either unit’s egress door opens onto a shared egress facility served by a single exit stair or ramp, a second means of egress isn’t needed if the building is sprinklered or each unit has separate, direct access from each storey to a balcony or to a window with an opening at least 1 m high and 0.55 m wide, its sill no more than 1 m above the floor and no more than 7 m above adjacent ground (9.9.9.3.(3), applying the window rules in 9.9.9.1.(2)(a) and (b)). | Items 5 and 6: protecting openings near unenclosed exterior exit stairs and ramps, and near exit doors, isn’t required when all smoke alarms in the house are photo-electric and interconnected. |
| Smoke alarms | In each dwelling unit and in ancillary and common spaces (9.10.19.1.); on each storey including basements, in each sleeping room and between the sleeping rooms and the rest of the storey (9.10.19.3.); permanently wired with battery backup (9.10.19.4.); a silencing device for no more than 10 min (9.10.19.6.). The City’s Secondary Suites Policy (December 16, 2013) lists interconnected photoelectric smoke alarms first among its basic life-safety requirements; its 2013 Example Plan shows ionization alarms, so go by the current code (policy, PDF). | — |
| CO alarms | 9.32.4.2.: with a fuel-burning appliance in a suite, a CO alarm inside each bedroom or within 5 m of each bedroom door (4); with one in a service room outside the suites, CO alarms in each adjoining suite and in the service room (5); in a house with a secondary suite, CO alarms are interconnected (7). | — |
| Ceiling height | At least 2.1 m over the minimum area in Table 9.5.3.1. (9.5.3.1.(1)). | Item 2: at least 1.95 m over the required area, with travel between the required areas of all rooms without dropping below 1.95 m; at least 1.85 m under beams and ducting, including over stairs. |
| Doorways and stairs | Doorways for doors at least 1,980 mm high (9.5.5.1.); 1,950 mm clear height over stairs (9.8.2.2.(3)). | Items 3 and 4: doorways within the suite for doors at least 1,890 mm high, except exit doors and doors serving public and exit corridors; 1,850 mm over stairs under existing beams and ducting, except stairs in a public or exit corridor. |
| Sound | 9.11.1.1.(2): the basic assembly above, construction rated at least STC 43, or a separating assembly and adjoining construction rated at least ASTC 40. | Item 9: resilient metal channel at 400 or 600 mm o.c. and another layer of at least 12.7 mm gypsum board on one side of an existing finished assembly, in place of the basic assembly. |
| Grab bars | 3.8.5.1.(2): one bathroom in a suite reinforced for future grab bars. | Item 1: not required in existing bathrooms serving the suite. |
Related: Secondary suite permit how-to (BC) · Duncan building permit guide · Duncan deck permit and build guide · Nanaimo secondary suite permit guide · Victoria secondary suite permit guide · Vancouver secondary suite permit guide · 30-second permit quiz
Most houses, suites, decks and garages fall under Part 9 of the BC Building Code 2024: buildings of 3 storeys or less, up to 600 m², with residential or certain other uses (Division A, 1.3.3.3). Bigger buildings fall under Part 3, which always needs registered professionals and Letters of Assurance (Division C, 2.2.7.1).
On a Part 9 project, the Code requires a registered professional (an engineer or architect who seals drawings and signs Letters of Assurance) only for parts outside Part 9. Examples are beams with point loads, girder trusses, engineered products, soil or foundation conditions beyond Part 9, and retaining walls that support a foundation. The province also recommends professional design for other retaining walls over 1.2 m. For the rest, the Code doesn’t say who must draw the plans. The city sets the drawing standard.
The City of Duncan doesn’t publish a rule on who may draw these plans. Ask the city before you hire anyone or draw them yourself.
Checked October 26, 2026: BC Building Code 2024 (PDF) · Guide to Letters of Assurance (PDF) · Letters of Assurance (gov.bc.ca) · EGBC guidelines · AIBC: does your project need an architect?
Yes, if you’re in the City of Duncan. Building Bylaw No. 3254 s.5.1 requires a building permit for work subject to the Building Code, and s.7.1(h) bans changing the use of part of a building without one. Many Duncan addresses are in North Cowichan or the CVRD instead, so check the City’s maps first.
Under Zoning Bylaw 3166 (consolidated August 24, 2026), the maximum gross floor area of an attached or detached suite in the LDR zone is 90 m², with one suite per primary dwelling unit. The City’s 2018 regulations sheet still shows a 40% limit, so confirm with Development Services.
The zoning bylaw requires 1 off-street space per dwelling unit (s.3.28.1), so a house with a suite needs two, and for a single-unit dwelling with a suite one space may be behind the other (s.3.25.4).
Under Fees and Charges Bylaw 3212, the building permit fee is $8 per $1,000 of value up to $100,000 ($50 minimum), plus a plan review fee at application ($50, $100 or $200 by value), plumbing at $12 per fixture and a $100 secondary suite inspection fee. By our own arithmetic, $60,000 of work would be a $480 permit fee.
DCC Bylaw 3234 has no secondary suite category, and for unlisted types the Director of Public Works and Engineering decides the most similar category. Ask the City whether a charge applies.
Under Flood Plain Management Bylaw 3236, living space must be above the flood construction level, without fill. The renovation exemption doesn’t apply when a renovation creates a new dwelling unit (s.7.1(b)), but the Director may grant a site-specific exemption (s.9.1).
No. Technical Safety BC issues electrical and gas permits, and says you must hire a licensed contractor if your property has a suite, whether or not it is occupied.
Independent information only. This guide is a planning aid, not legal, engineering or building-code advice. Codes and bylaws change, and the building official for your address has the final say. Confirm every requirement before you design, apply or dig.
This guide relies on the official pages below. Rules, fees and processes change, so check the authority before you apply or spend money.
Links checked October 1, 2026. Found an error or a broken link? Report it.