Building a deck in Duncan: permit to final inspection

By Mark Dupuis · Last reviewed: October 26, 2026

Built from the City of Duncan permit sheets, fee schedule and Building Bylaw No. 3254 (2026), the CVRD and North Cowichan deck rules, the BC Building Code 2024 and BC Housing’s deck guide · Independent site — not a municipality or the Province

This is the start-to-finish version of building a deck inside the City of Duncan: which local government you actually apply to, the forms, the drawings, the BC Building Code rules the inspector checks, each inspection, a materials list and the mistakes that most often cause a failed inspection. The short answer on permits: the City’s own Do I need a building permit? sheet says you need one to construct, cover or enclose porches and exterior decks, and it doesn’t list a low-deck exemption. Starting without one means a double permit fee. Sources: City of Duncan, Do I need a building permit? (PDF).

On this page

1. Step 1: Confirm you are actually in the City of Duncan
2. Step 2: Zoning, development permit areas and title
3. Step 3: Permit steps and forms
4. Step 4: Drawings to prepare
5. Step 5: Footings, framing, ledger, guards and stairs
6. Step 6: Inspections in Duncan
7. Materials list (example deck)
8. Common failure points
9. Frequently asked questions

Step 1: Confirm you are actually in the City of Duncan

The City of Duncan is small. It is surrounded by the Municipality of North Cowichan, and the Cowichan Valley Regional District (CVRD) looks after the rural electoral areas beyond that. Plenty of addresses with a “Duncan” mailing address are not in the City, and each of the three governments runs its own building department with its own deck rules:

How to confirm which one applies to your address:

1. Open the City’s “Do I live in the City of Duncan?” maps page. It links the City streets map and the City address and zoning map. If your parcel is inside the City boundary on those maps, Duncan is your building authority.
2. If it isn’t, search the address in the CVRD Web Map. The CVRD says the map’s identify tool shows the electoral area and zoning for parcels in its electoral areas (CVRD realtor and developer resources). If the parcel shows no electoral area, it is likely in a municipality such as North Cowichan, so check with North Cowichan’s building department.
3. Still unsure? Phone Duncan Development Services at 250-746-6126. The City’s building page says staff will help you work out which permits you need, and may have historical information about your property (source).

The rest of this guide is written for City of Duncan parcels. If you’re in North Cowichan or a CVRD electoral area, the BC Building Code sections below still apply, but the permit steps, forms and exemptions are different. Start with our Cowichan Valley (CVRD) permit guide.

Step 2: Zoning, development permit areas and title

A building permit only answers whether the deck is built safely. Where it can go is a separate question, and it’s worth settling first:

• Zoning. Duncan’s zoning map shows your zone. Setbacks, lot coverage and height come from the zoning bylaw, and a deck has to meet them even though the house may not. The City doesn’t publish deck-specific setbacks on its permit pages, so verify the numbers for your zone with Development Services.
• Development permit areas. The City’s building page warns that zoning, use and other factors may require a development permit first, and that it must be approved before the building permit can be issued (source). The Do I need a building permit? sheet singles out the Downtown Development Permit Area (even painting needs a permit there) and the Hazard Lands DPA. Check the City’s development permit areas page before you draw anything.
• Title. Duncan’s Building Bylaw No. 3254 (adopted April 27, 2026) lets the building official ask for current title searches and copies of covenants, rights-of-way and easements, with their plans (s.8.1(l)). A deck footing sitting on a registered right-of-way is a common surprise, so order the title early.
• Survey near a setback line. Under s.14.2 of the same bylaw, if any footing comes within 0.5 m of a required setback, right-of-way or easement, you must give the building official a BC land surveyor’s certificate of footing locations, and concrete can’t be poured until it’s accepted. Designing the deck a little further from the line can save you a survey.

Step 3: Permit steps and forms

1. Talk to the building inspector. Call 250-746-6126 or email developmentservices@duncan.ca with a sketch and your address. Ask three things: whether a development permit applies, what drawing sheet size they will accept for a deck, and whether they want to see footing holes or forms before you pour.
2. Fill in the application. Use the City’s Building Permit Application (PDF). It asks for the civic address, legal description, owner and applicant details, construction type (tick Addition or Renovation), a proposal description, the estimated value of construction and the zoning. If someone other than the registered owner applies, the owner must also sign. The form states that incomplete applications will not be accepted.
3. Pay the plan review fee when you apply. The application form says fees are due at the time of application and are based on the estimated value. The plan review fee is $50 up to $25,000 of value, and the first plan check is credited toward the building permit fee (application form).
4. Review and permit fee. The building permit fee on the City fee sheet is $8 per $1,000 of value up to $100,000 ($50 minimum). So a deck valued at $15,000 works out to $120 (our arithmetic from the bylaw rates) in permit fee, plus the plan review fee (credited as above). Work started without a permit is charged double.
5. Permit issued. Bylaw 3254 s.17 requires the permit to be posted conspicuously on site, with the approved plans and inspection records available for the inspector during working hours.
6. Start within 180 days, finish within two years. Under s.10.1, a permit expires if work isn’t substantially started within 180 days, stops for 180 days, or isn’t finished (final inspection notice) within two years of issue. The building official can extend it once, for up to a year (s.10.2).

Adding deck lighting or an outdoor receptacle? That is a separate electrical permit. Duncan isn’t on Technical Safety BC’s list of local governments that issue their own electrical permits, so electrical goes to Technical Safety BC (TSBC jurisdiction list).

Step 4: Drawings to prepare

Duncan doesn’t publish a deck-specific drawing checklist. Its new-building requirements sheet is written for whole buildings. What the City does set is the general rule in Bylaw 3254 s.8.2: submissions come in paper and PDF, two full-size sets (36 × 48 in.), unless a building official says smaller sets or electronic-only submission is fine. For a deck, ask. As a checklist of what a deck reviewer needs to see, the neighbouring North Cowichan deck checklist is a good model: sheets no smaller than 11 × 17 in., a floor plan at 3/16 in. = 1 ft or larger, elevations at 1/8 in. = 1 ft (North Cowichan deck checklist, PDF). Plan on these sheets:

• Site plan to scale: property lines, house, the deck footprint with distances to every lot line, rights-of-way and easements, north arrow.
• Footing plan: post locations, footing sizes and depth below finished grade, and the soil you expect to bear on.
• Framing plan: ledger (or freestanding beam), beam sizes and spans, joist size, spacing and span, hangers and connectors, post size.
• Cross-section: footing to guard, with the height of the walking surface above grade, decking, ledger connection and flashing, guard height and baluster spacing.
• Stair detail if you have stairs: number of risers, rise and run, stringer size and spacing, handrail and guard.
• Elevation(s): how the deck meets the house, doors opening onto it, and heights above grade.

Want a rough layout first? Our free deck plan sketch maker draws a watermarked, to-scale planning sketch from your own entries: a site plan, a deck plan, a side elevation and a cross-section, on 11 × 17, 24 × 36 or 36 × 48 in. sheets. It’s for planning and for talking to the City or a designer, not for submitting, and it never sizes any member.

Deck framing follows Part 9’s rules or is designed to Part 4 (BCBC 9.4.1.1). BC Housing’s deck guide says a hot tub needs significant structural upgrades. Ask the City whether your design needs engineered drawings. The building official can also ask for professional letters of assurance (Building Bylaw No. 3254 s.8.1(i) and s.16.1(d)).

Step 5: Footings, framing, ledger, guards and stairs

Duncan applies the BC Building Code. A permit applied for on or after March 8, 2024 is under the BC Building Code 2024, and Part 9 covers a house deck (Province of BC, BC Building Code 2024). The section numbers below were checked against the official BCBC 2024 PDF. They are summaries, not the code wording, so check the text and your approved drawings.

Footings and foundations (9.12, 9.15)

• Decks support occupants, so the code treats them as buildings: Section 9.15 footing requirements apply to them (Note A-9.15.1.1.).
• Footings bear on undisturbed soil, rock or compacted granular fill (9.15.3.2.). Excavations go down to undisturbed soil (9.12.2.1.).
• Minimum footing depth is set by soil type and drainage in Table 9.12.2.2. For a foundation with no heated space, such as a deck’s, the table’s row for clay or soils not clearly defined calls for at least 1.2 m, and never less than the depth of frost penetration (Table 9.12.2.2.). Sentence 9.12.2.2.(5) allows lesser depths where experience with local soil conditions shows they’re satisfactory, or where the foundation is designed for them. Sentence 9.12.2.2.(7) relaxes that depth only for a deck that is one storey, no more than 55 m², no more than 600 mm from finished ground to the underside of the joists, carries no roof and isn’t attached to another structure (unless differential movement is shown not to matter). An attached deck doesn’t get that relaxation by default.
• Footing thickness is at least 100 mm, and not less than the footing’s projection beyond the post or pier (9.15.3.8.). Column footing areas come from Table 9.15.3.4. and are adjusted for post spacing (9.15.3.7.).
• Posts: wood columns at least 140 × 140 mm (or 184 mm round) unless calculations show smaller is adequate (9.17.4.1.). They must be separated from concrete that touches the ground by poly or Type S roll roofing (9.17.4.3.), and centred on the footing (9.17.2.1.).
• Keeping wood dry: BC Housing recommends that concrete footings and piers extend at least 152 mm (6 in.) above grade to limit the moisture exposure of the deck’s wood (p. 11). It also suggests setting posts in a metal saddle anchor or post base with drainage, such as weep holes, rather than end grain on the concrete; typical stand-off height is 25 mm (1 in.) (p. 20, BC Housing deck guide (PDF)). These are best-practice recommendations, not code minimums.
• Anchorage: exterior posts must resist uplift and lateral movement (9.23.6.2.). For low decks (600 mm or less to the joists), the small freestanding, roofless, one-storey platforms described in 9.23.6.2.(3) are excused.

Framing (9.4, 9.23)

• Design load: a deck serving one dwelling carries the specified roof snow load or 1.9 kPa, whichever is greater (9.4.2.3.). Deflection limit for deck beams, joists and decking serving one dwelling is L/240 (Table 9.4.3.1.).
• Joist and beam sizes come from the span tables referenced in 9.23.4.2. Your drawings must show the lumber species, grade, size and spacing that the table relies on.
• Spacing cap: Section 9.23’s framing rules apply only where the framing members are spaced no more than 600 mm on centre; beyond that, framing and fastening must be designed under Subsection 4.3.1 (9.23.1.1.). BC Housing’s guide states the same 600 mm (24 in.) joist-spacing limit for Part 9 and says wider spacing is possible only in a Part 4 design by a professional engineer (p. 13, BC Housing deck guide (PDF)).
• Joists framed into the side of a wood beam sit in joist hangers or on ledger strips of the size and nailing given in 9.23.9.2.(2). Joists need at least 38 mm of end bearing (9.23.9.1.), beams at least 89 mm (9.23.8.1.).
• Nailing follows Table 9.23.3.4. Posts must be laterally supported against racking (9.17.2.2.), except low decks with no superstructure where the joists are 600 mm or less above ground. BC Housing’s guide says all decks over 600 mm (24 in.) above ground must be laterally supported to resist racking. In practice that means tying the deck to the house (a ledger-attached deck) or bracing between the posts and the members they carry (a freestanding deck), and large decks on tall posts may need extra post bracing or building connections (p. 14, BC Housing deck guide (PDF)).
• Decking gap: BC Housing recommends at least 6 mm (¼ in.) between deck boards to allow for wood movement, drainage and drying, and more where organic matter tends to collect on the site (p. 20, BC Housing deck guide (PDF)).
• Decay: structural wood must be preservative-treated where it is within 150 mm of finished ground, or where it is exposed to rain in a configuration that traps moisture in a climate with a moisture index over 1.00 (9.3.2.9.(3)). Exterior wood steps can’t touch the ground unless treated (9.8.9.3.).

Ledger attachment

This is where decks fail. BCBC 2024 has no deck-ledger fastening schedule. BC Housing’s illustrated guide says plainly that the code doesn’t give comprehensive guidance on ledger fastening patterns, and calls ledger attachment a common point of failure (BC Housing, Building Safe and Durable Wood Decks and Balconies (PDF)). The guide’s best-practice recommendations:

• Lag screws or through-bolts with washers, 13 mm (½ in.) diameter, fully penetrating the ledger and the house rim joist, installed staggered. Spacing depends on joist span: its table gives 381 mm on centre for 13 mm lag screws at a 3.66 m joist span.
• A ledger of at least 38 × 184 mm pressure-treated lumber.
• Flashing over the ledger and a drainage and drying strategy so water doesn’t get into the wall or rot untreated framing.

Treat these as best practice to show on your drawings, not code minimums. Duncan’s building official decides what’s acceptable, and a freestanding deck (its own beam and posts along the house) avoids the ledger question entirely.

Guards (9.8.8)

• Required on any open side where the walking surface is more than 600 mm above the adjacent surface within 1.2 m (9.8.8.1.). That includes exterior stairs and landings.
• Height: 900 mm minimum for an exterior guard serving one dwelling where the deck is no more than 1,800 mm above finished ground. Above that, 1,070 mm (9.8.8.3.). On stairs, measure from a line through the nosings.
• Openings must stop a 100 mm sphere. The triangle formed by a stair riser, tread and bottom rail must stop a 150 mm sphere (9.8.8.5.).
• Loads are in Table 9.8.8.2. (for example, a 0.5 kN/m or 1.0 kN concentrated horizontal load at the top of a guard serving a dwelling). The non-climbable design rule in 9.8.8.6. applies where the guard protects a level more than 4.2 m above the one below.
• Glass in guards must be laminated or tempered safety glass, or wired glass (9.8.8.7.).

Stairs and handrails (9.8)

• Private stairs (serving one dwelling): rise 125–200 mm, run 255–355 mm (Tables 9.8.4.1. and 9.8.4.2.). Keep every riser and tread the same within the tolerances in 9.8.4.4.
• Exterior stairs serving a single dwelling unit: at least 860 mm wide (9.8.2.1.(4)).
• Handrails aren’t required on exterior stairs of a single dwelling with 3 risers or fewer. With more than 3 risers, one handrail is enough (9.8.7.1.(3) and (4)). Required handrails are 865–1,070 mm high (9.8.7.4.).
• Wood stringers: at least 90 mm effective depth and 235 mm overall, supported top and bottom, spaced no more than 900 mm apart for a single dwelling (9.8.9.4.).
• Landings are required at the top and bottom of a flight, with specific exceptions for short secondary-entrance stairs and unobstructed bottoms (9.8.6.2.).

Step 6: Inspections in Duncan

Section 14.1 of Building Bylaw No. 3254 lists every inspection stage the City can require. Each must be inspected and accepted in writing before the work is covered. For a typical deck, the stages that apply are:

• Give at least 48 hours’ notice when you request an inspection (s.14.3). The inspector doesn’t have to come at the time you ask for (s.14.4).
• A callback inspection costs $50 on the City fee sheet, so don’t book before you’re actually ready.
• Keep the permit posted and the approved plans on site (s.17).

Printable: take the deck inspection checklist (before you book, footings, framing, final) to the site before each inspection.

Budget the materials: the deck, shed and fence materials cost calculator counts joists, deck boards, posts, concrete bags, hangers, post bases and screws for your size of deck, then prices them with dated BC retailer prices.

Materials list (example deck)

General guidance for one example: a 3.66 × 4.88 m (12 × 16 ft) deck attached along the long side, joists at 400 mm (16 in.) on centre running out from the house, walking surface about 900 mm above grade. Quantities are rounded, with no prices. Your approved drawings and the span tables set the real sizes.

Common failure points

• Wrong jurisdiction. Applying to Duncan for a North Cowichan or CVRD parcel, or assuming the CVRD’s 24 in. exemption applies inside the City. It doesn’t: Duncan’s sheet lists all exterior decks.
• Pouring before the forms inspection, or pouring near a setback line before the surveyor’s certificate is accepted (s.14.2).
• Ledger fastened with nails or into cladding, with no flashing. Inspectors look hard at this, and it is BC Housing’s number-one failure point.
• Guard too low once the finished decking is on, or balusters that let a 100 mm sphere through at the ends of runs and at the stair.
• Uneven stair risers because the landing pad height wasn’t planned, or stringers spaced too far apart for the tread material.
• Posts sitting directly on concrete in contact with the ground without a separation layer (9.17.4.3.), or undersized posts without calculations.
• Covering the framing (decking, skirting) before the framing inspection.
• Adding a roof or hot tub later without revising the permit. Both change the loads and usually the footings.

Related: Duncan building permit guide (fees, timelines, contacts) · Duncan secondary suite permit guide · Printable deck inspection checklist · Deck permit how-to for BC · Deck and shed rules by city · 30-second permit quiz

Frequently asked questions

Do I need a permit for a deck in Duncan?

Yes, if you are in the City of Duncan. The City’s Do I need a building permit? sheet says a permit is needed to construct, cover or enclose porches and exterior decks, and it lists no low-deck exemption. Work started without a permit is charged a double permit fee.

My address says Duncan. How do I know if the City is my building authority?

Check the City’s “Do I live in the City of Duncan?” maps (streets and zoning maps). If your parcel is outside the City, search it on the CVRD Web Map, which shows the electoral area for CVRD parcels. Otherwise it is likely North Cowichan. If in doubt, call Duncan Development Services at 250-746-6126.

How much is a deck permit in Duncan?

The City fee sheet sets the building permit fee at $8 per $1,000 of construction value up to $100,000, with a $50 minimum. A plan review fee ($50 up to $25,000 of value) is paid at application and the first plan check is credited toward the permit fee. A $15,000 deck works out to $120 (our arithmetic from the bylaw rates) in permit fee.

What inspections will a Duncan deck need?

Building Bylaw No. 3254 s.14.1 lists the stages. For a deck, expect a forms inspection before concrete is poured, a framing inspection before anything covers the framing, and a final inspection. Give at least 48 hours’ notice. A callback inspection costs $50.

How high does a deck guard have to be in BC?

Under BC Building Code 2024 Article 9.8.8.3., an exterior guard serving one dwelling must be at least 900 mm high where the deck is no more than 1,800 mm above finished ground, and 1,070 mm above that. Guards are required where the drop is more than 600 mm (9.8.8.1.).

Does the BC Building Code say how to bolt a deck ledger?

No. BCBC 2024 has no deck-ledger fastening schedule. BC Housing’s deck guide recommends 13 mm lag screws or through-bolts, staggered, fully through the ledger and rim joist, with spacing tied to joist span, plus flashing. Show your ledger detail on the drawings and let the building official confirm it.

How long is a Duncan building permit valid?

Under Bylaw 3254 s.10.1 the permit expires if work doesn’t substantially start within 180 days, stops for 180 days, or isn’t finished within two years of issue. The building official can extend it once, for up to one year.

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.