---
title: Duncan secondary suite and carriage house rules
question: "Can I add a secondary suite or a carriage house?"
place: Duncan, British Columbia, Canada
place_path: ca/bc/duncan
category: Building, renovating and your property
owner: municipal
owner_body: City of Duncan
sources_read: 2026-11-05
review: machine_checked
canonical: "https://govhandbook.com/ca/bc/duncan/secondary-suite/"
json: "https://govhandbook.com/ca/bc/duncan/secondary-suite.json"
---

# Duncan secondary suite and carriage house rules

**Question:** Can I add a secondary suite or a carriage house?

**Short answer:** Yes. The City of Duncan's zoning allows one attached suite or one detached suite (in an accessory building) per primary dwelling in the Low Density Residential zone, up to 90 m². A building permit is required, and the City offers pre-approved plans with waived plan review and permit fees.

**Who handles it:** Municipal (City of Duncan, https://duncan.ca)  
**Cost:** Plan review and building permit fees are waived if you use the City's pre-approved plans unchanged; otherwise standard building fees apply. Secondary suite inspection $100. Development cost charges are not payable on a first new secondary suite.  
**How long:** Not stated on the City's pages.  
**Where:**
- Phone: Development Services, 250-746-6126
- Email: Development Services, DevelopmentServices@duncan.ca
- Email: Building Department, Building@duncan.ca
- In person: City Hall, 200 Craig Street, Duncan, BC V9L 1W3

## Key facts

- **Secondary suite allowed:** Attached secondary suites are allowed in Low Density Residential (LDR), and in Medium and High Density Residential only in multi-unit rowhouse dwellings. Zoning permits up to four dwelling units on LDR parcels.
  - Source: [Zoning Bylaw No. 3166, 2017 (PDF, consolidated to August 24, 2026), section 4.3, s. 4.2.1, 4.8.2, 4.1.1](https://duncan.civicweb.net/document/175322)
  - Official wording: "Secondary Suite, Attached" … "An attached secondary suite is only permitted in a multi-unit rowhouse dwelling" … "permit up to four dwelling"
  - Source: [Small-Scale Multi-Unit Housing (SSMUH), Secondary Suites, and ADUs, SSMUH page](https://duncan.ca/city-hall/planning-and-development/ssmuh/)
  - Official wording: "permit up to 4 dwelling units on parcels zoned Low Density Residential (LDR)"
  - Check: wording matched the official text retrieved 2026-11-06
- **Coach house or garden suite allowed:** Allowed as an accessory use in the LDR zone (one detached secondary suite per primary dwelling, in an accessory building on a parcel with a single-unit dwelling). (Sources differ: The City's Secondary Suites Regulations PDF says detached suites require a minimum 600 m² lot, but the current zoning bylaw (amended May 2025) states no lot-size minimum for them; the City's web page says detached suites 'may be permitted where parcels meet the minimum lot size'. Check with the City.)
  - Source: [Zoning Bylaw No. 3166, 2017 (PDF, consolidated to August 24, 2026), section 4.3, s. 4.2.1, definitions](https://duncan.civicweb.net/document/175322)
  - Official wording: "Secondary Suite, Detached" … "means a secondary dwelling unit located in an accessory building" … "on the same parcel as a single-unit dwelling"
  - Check: wording matched the official text retrieved 2026-11-06
- **Limits:** LDR: one attached or one detached secondary suite per primary dwelling unit; maximum floor area 90 m². Detached suites must be at least 2.5 m from the main dwelling; an accessory building with a second-storey detached suite may be 7.5 m high. The zoning text sets no owner-occupancy requirement. (Sources differ: The older Secondary Suite Regulations PDF gives percentage limits (attached 40%, detached 60% of the house, or 90 m²) that the current zoning text does not repeat. Searched zoning text for 'owner' occupancy: not checked in detail.)
  - Source: [Zoning Bylaw No. 3166, 2017 (PDF, consolidated to August 24, 2026), section 4.3, s. 4.3.2, 4.3.3, 3.11.2, 4.3.1](https://duncan.civicweb.net/document/175322)
  - Official wording: "The maximum number of suites is one attached secondary suite or one detached" … "secondary suite per primary dwelling unit" … "The maximum gross floor area of an attached secondary suite or detached" … "suite is 90 m2" … "Detached secondary suites must be sited at least 2.5 m from a principal" … "7.5 m for buildings with a detached secondary suite on" … "The maximum gross floor area of an attached secondary suite or detached secondary"
  - Check: wording matched the official text retrieved 2026-11-06
- **Parking:** 1 off-street space per dwelling unit, so one for the suite as well as one for the main dwelling. A second space may sit behind the first with a shared access. (Sources differ: The older Secondary Suite Regulations PDF says one extra space for the suite plus two for the main dwelling; the current zoning bylaw says 1 per dwelling unit, so it is followed.)
  - Source: [Zoning Bylaw No. 3166, 2017 (PDF, consolidated to August 24, 2026), section 4.3, s. 3.28.1, 3.25.4](https://duncan.civicweb.net/document/175322)
  - Official wording: "Residential Use" … "1 per dwelling unit" … "may be arranged such that one space is located" … "behind the other space"
  - Source: [Small-Scale Multi-Unit Housing (SSMUH), Secondary Suites, and ADUs, SSMUH page](https://duncan.ca/city-hall/planning-and-development/ssmuh/)
  - Official wording: "One on-site parking stall is required for each dwelling unit."
  - Check: wording matched the official text retrieved 2026-11-06
- **Permits:** A building permit is required (plans meeting the 2024 BC Building Code). Detached suites also need Homeowner Protection Office approval or exemption. Buildings with three or more units need a Development Permit. A $100 secondary suite inspection fee applies. Building permit and plan review fees are waived if you use the City's pre-approved ADU plans unchanged.
  - Source: [Small-Scale Multi-Unit Housing (SSMUH), Secondary Suites, and ADUs, SSMUH page](https://duncan.ca/city-hall/planning-and-development/ssmuh/)
  - Official wording: "A building permit application to the City is still required" … "All multi-unit residential buildings (defined as a building with three or more dwelling units) will need to be authorized by a Development Permit" … "Building Permits are issued for construction that conforms to the 2024 BC Building Code"
  - Source: [Secondary Suites, Secondary Suites page](https://duncan.ca/city-hall/planning-and-development/building-permits-inspection/secondary-suites/)
  - Official wording: "Freestanding residential buildings require Homeowner Protection Office approval or exemption"
  - Source: [Fees and Charges Bylaw No. 3212, 2020 (PDF, consolidated to August 24, 2026), Schedule E](https://duncan.civicweb.net/document/181386)
  - Official wording: "7. Secondary Suite Inspection Fee" … "$100.00"
  - Check: wording matched the official text retrieved 2026-11-06
- **Bylaw:** Zoning Bylaw No. 3166, 2017 (amended to August 24, 2026), s. 4.3 and definitions
  - Source: [Zoning Bylaw No. 3166, 2017 (PDF, consolidated to August 24, 2026), section 4.3, Part 4 LDR](https://duncan.civicweb.net/document/175322)
  - Official wording: "Low Density Residential Zone" … "Secondary Suite, Detached"
  - Check: wording matched the official text retrieved 2026-11-06

## How it works

The City of Duncan's [Zoning Bylaw](https://duncan.civicweb.net/document/175322) allows one attached or one detached secondary suite per primary dwelling in the Low Density Residential (LDR) zone. A detached suite is an accessory use in an accessory building on a parcel with a single-unit dwelling. In Medium and High Density Residential zones, attached suites are allowed only in multi-unit rowhouse dwellings. LDR zoning also permits up to four dwelling units on a parcel. Not all housing forms are allowed on all parcels, so check your lot first.

## Steps

1. Confirm your zone with Development Services at 250-746-6126.
2. Check flood plain status: LDR parcels east of the Trans Canada Highway are in a flood plain with extra requirements.
3. Decide whether to use the City's pre-approved ADU plans or a custom design.
4. For a detached suite, get Homeowner Protection Office (BC Housing) approval or an exemption.
5. Apply for a building permit with plans meeting the 2024 BC Building Code. A driveway access permit is needed for any new access.

## Good to know

- Maximum suite floor area is 90 m². A detached suite must be at least 2.5 m from the main dwelling, and one on the second storey of an accessory building may be 7.5 m high.
- Parking is 1 off-street space per dwelling unit, so one for the suite as well as one for the main dwelling.
- The City's older Secondary Suite Regulations PDF says otherwise on some points (a 600 m² minimum lot for detached suites, percentage size limits, more parking). The current zoning bylaw does not repeat these, so confirm with the City.
- Buildings with three or more units need a Development Permit.
- The City's pages mention an additional utility charge for secondary suites; ask Development Services what applies.
- Pre-approved plans waive only the plan review and permit fees; other costs such as the $100 suite inspection still apply.

## What you'll need

- Building Permit Application with plans meeting the 2024 BC Building Code
- Homeowner Protection Office (BC Housing) approval or exemption for a detached suite

## Official forms and pages

- [Small-Scale Multi-Unit Housing, Secondary Suites and ADUs page](https://duncan.ca/city-hall/planning-and-development/ssmuh/)
- [Secondary Suites page](https://duncan.ca/city-hall/planning-and-development/building-permits-inspection/secondary-suites/)
- [Secondary Suite Regulations (older PDF)](https://duncan.ca/download/secondary-suites-building-requirements/)

## Related questions

- [Duncan building permits: when you need one and how to apply](https://govhandbook.com/ca/bc/duncan/building-permit.md)
- [Duncan building permit fees](https://govhandbook.com/ca/bc/duncan/building-permit-fees.md)
- [Duncan zoning: find your zone and what it allows](https://govhandbook.com/ca/bc/duncan/zoning-lookup.md)

## The same question elsewhere

- [Secondary suite and carriage house rules in British Columbia, by municipality](https://govhandbook.com/ca/bc/secondary-suite.md)
- [North Cowichan](https://govhandbook.com/ca/bc/north-cowichan/secondary-suite.md)
- [Ladysmith](https://govhandbook.com/ca/bc/ladysmith/secondary-suite.md)
- [North Saanich](https://govhandbook.com/ca/bc/north-saanich/secondary-suite.md)
- [Lake Cowichan](https://govhandbook.com/ca/bc/lake-cowichan/secondary-suite.md)
- [Sidney](https://govhandbook.com/ca/bc/sidney/secondary-suite.md)
- [Central Saanich](https://govhandbook.com/ca/bc/central-saanich/secondary-suite.md)

## Sources

- [Small-Scale Multi-Unit Housing (SSMUH), Secondary Suites, and ADUs, City of Duncan](https://duncan.ca/city-hall/planning-and-development/ssmuh/) (read 2026-11-05)
- [Secondary Suites, City of Duncan](https://duncan.ca/city-hall/planning-and-development/building-permits-inspection/secondary-suites/) (read 2026-11-05)
- [Zoning Bylaw No. 3166, 2017 (PDF, consolidated to August 24, 2026), section 4.3](https://duncan.civicweb.net/document/175322) (read 2026-11-05)
- [Fees and Charges Bylaw No. 3212, 2020 (PDF, consolidated to August 24, 2026)](https://duncan.civicweb.net/document/181386) (read 2026-11-05)
- [Secondary Suite Regulations (PDF), City of Duncan](https://duncan.ca/download/secondary-suites-building-requirements/) (read 2026-11-05)

_Checked by script, not yet by a person: the official wording behind 6 of 6 facts was matched to the official text. Gov Handbook is an independent guide, not affiliated with City of Duncan. How answers are checked: https://govhandbook.com/methods/ · Canonical page: https://govhandbook.com/ca/bc/duncan/secondary-suite/_