Do I need a permit to build a deck?

Yes, in most cases. Under the 2021 International Residential Code (IRC), a deck needs no building permit only when four things are all true. It is no more than 200 sq ft (18.58 m²). It is no more than 30 in (762 mm) above the ground at any point. It is not attached to the house. And it is not the landing outside the house's required exit door. A deck fixed to the house on a ledger fails the third test at any size, so under the model code it always needs a permit.

Towns rewrite this rule, and the line moves. Portland, Oregon uses height alone. Edmonton, Alberta stops at 0.6 m (23 5/8 in), and Red Deer and Greater Sudbury at 2 ft. England has no deck permit as such, but decking over 0.3 m (11.8 in) needs planning permission. The rest of the garden is in outdoor room dimensions.

What the code means by a deck "without a permit"#

A building permit is approval from your town's building department. It says a structure meets the building code, so it will hold its load and be safe to use. An inspector checks the work at set stages.

A deck here is an open, raised floor outdoors, with no roof or walls. Edmonton puts it plainly: "an open, elevated platform". A patio is a surface laid on the ground, and it is not a deck.

Above grade means the height from the ground to the top of the deck boards. The IRC says "at any point", so on a slope the high corner counts.

Attached means fixed to the house. Most attached decks hang one edge on a ledger: a board bolted to the house wall that carries the joists. A freestanding deck, often called a floating deck, stands on its own posts or blocks instead. The IRC allows both. Section R311.5 says a deck "shall be positively anchored to the primary structure" or "designed to be self-supporting".

An exempt deck is free of the permit, not free of the code. Section R105.2 says the exemption "shall not be deemed to grant authorization for any work to be done in any manner in violation of the provisions of this code". So the footings, the framing and any guard still have to be right. No one will inspect them.

The four tests in IRC R105.2, word for word#

Section R105.2 lists the work that needs no permit. Under "Building", the last item reads:

"Decks not exceeding 200 square feet (18.58 m2) in area, that are not more than 30 inches (762 mm) above grade at any point, are not attached to a dwelling and do not serve the exit door required by Section R311.4."

The sentence joins its four tests with "and". A deck must pass every one.

"Not exceeding" and "not more than" both let the limit itself pass. A deck of exactly 200 sq ft at exactly 30 in is exempt under the model text.

The exit door test needs one more step. The IRC requires one egress door for each home in section R311.2: "Not less than one egress door shall be provided for each dwelling unit." That is the exit door the exemption means. A deck that serves as the landing outside it is not exempt, even if it is small, low and freestanding. A deck off some other door can pass this test, so ask which door your house plans name as the egress door.

One detail an expert may not have seen: the exemption points to section R311.4. In the 2021 text, R311.4 is headed "Vertical Egress" and covers stairs and ramps from upper floors. The egress door itself is in R311.2. The meaning is clear either way, but if you look up R311.4 to check, you will find stairs, not doors.

Worked through: one 12 x 16 ft deck at 24 in, eight rulebooks#

Take a common plan and walk it through each rule. Suppose a deck is 12 x 16 ft (3.66 x 4.88 m), which is 192 sq ft (17.8 m²). Its boards sit 24 in (610 mm) above level ground. It is built two ways: first on a ledger at a back door, then freestanding with its own posts. The house's egress door is at the front, so the deck does not serve it. Each cell repeats a ruling made elsewhere on this page.

Read the middle column first. The freestanding deck at 24 in passes the US model code with 6 in (152 mm) to spare. It then fails every Canadian rule here. Edmonton's line is 0.6 m, which is 23 5/8 in, so a 24 in deck misses it by 3/8 in (10 mm). Red Deer and Sudbury say "24 inches or more" and "two feet or more", so 24 in is the first height that needs a permit.

Drop the boards by 1 in, to 23 in (584 mm), and all three Canadian rules pass. England does not. Its line is 0.3 m, and the deck is about twice that. To stay inside it, the walking surface has to sit at 11 3/4 in (298 mm) or lower. A "12 in" deck is 305 mm, which is 5 mm over.

The ledger column shows the attachment test doing its work. Under the model IRC, the same deck at the same height needs a permit once it is bolted to the house. Portland names no attachment test, so the ledger changes nothing there.

Why "30 inches" and "200 square feet" each travel alone#

Many pages give only one of the numbers, and both numbers are real. They are quoted alone because each one belongs to a better known rule.

The 200 sq ft figure is the shed rule. The same R105.2 list opens with "one-story detached accessory structures, provided that the floor area does not exceed 200 square feet (18.58 m2)". The deck item uses the same area, so people read it as the whole test. The site's guide to how big a shed can be without a permit covers that rule and its local changes.

The 30 in figure is the guard rule. Section R312.1.1 requires a guard where a walking surface is "more than 30 inches (762 mm)" above the grade below. Deck sizes and railing heights works through that trigger and the 36 in (914 mm) guard. Because the two rules share one number, a deck low enough to skip the guard sounds low enough to skip the permit.

Some towns also publish height as the only test. So the true answer is the longer one: four tests in the model code, and whatever your town changed.

Portland and Edmonton drop the size test#

Two cities show how far local rules can move from the model text. Both decide on height alone.

Portland, Oregon. Its Brochure 3 says building permits "are not required for decks where no part of the walking surface is more than 30 inches above adjacent grade and no portion of the deck is closer than three feet to an adjacent property line." There is no area test and no attachment test. The city's own deck project guide asks for the height "3 feet from where the perimeter of the deck will be", which is the guard rule's way of measuring. Portland adds that "zoning requirements still apply".

Edmonton, Alberta. The city lets a deck skip the building permit when it meets all of four tests. It "is 0.6 metres (23 ⅝ inches) or less above the ground at every point". It "serves only a single residential unit". It "does not have a roof or walls". And it "does not support heavy loads", where the city's examples are a gazebo or masonry. Edmonton runs a second permit, a development permit. A deck skips that one too if it is 1.2 m (3 ft 11 in) or less, sits wholly in a back or interior side yard, and meets the city's other tests, such as no roof.

So a large attached deck under 0.6 m needs no building permit in Edmonton, but would need one under the model IRC.

Red Deer, Sudbury and North Vancouver: about 2 ft#

Three more Canadian towns put the line near 2 ft, with small differences in the wording.

Red Deer, Alberta. Its deck page says: "If your deck is 24 inches or more above the ground, you will need to apply for a Building Permit." At 9 in (229 mm) or less the city calls it a patio, and no permits are needed. Between 10 and 24 in, a development permit is needed only for a variance. A covered deck at any height needs a building permit.

Greater Sudbury, Ontario. The city says you need a building permit "if it will be two feet or more above the ground" or if "your deck will be covered by a permanent roof". It publishes separate guides for attached decks and for detached decks under and over 1.8 m (6 ft).

District of North Vancouver, British Columbia. Its guide to building decks in single family zones says "Decks less than 2 ft (600 mm) in height and detached decks less than 108 sq.ft. (10m2) in area do not require a building permit". The next line says a detached deck "higher than 2 ft. (600 mm)" needs one, so the size clause does not lift the height line. Read it with the district before you rely on it.

All three need a permit at exactly 2 ft, which is why the 24 in deck in the worked case fails each.

England: decking over 0.3 m needs planning permission#

In England the rule that sets a deck's height is a planning rule: the General Permitted Development Order 2015. This page does not cover the Building Regulations. Permitted development is work the law allows without an application for planning permission, within set limits.

Class A covers extensions to the house, and Class E covers buildings and enclosures in the garden. Both exclude "a verandah, balcony or raised platform", in paragraphs A.1(k)(i) and E.1(h). The Order then defines the word: "'raised' in relation to a platform means a platform with a height greater than 0.3 metres". So decking over 0.3 m (11.8 in) needs planning permission, attached or not.

The government's technical guidance spells out the low case. It says garden decking "will therefore be permitted development under Class E subject to it not exceeding this 0.3m height limit and subject to the other limits and conditions under this Class." One of those conditions caps the ground covered by "buildings, enclosures and containers" at 50 per cent of the garden around the house. Class E also gives no allowance within the grounds of a listed building.

How the 0.3 m is measured matters on a slope. The guidance defines ground level as "the surface of the ground immediately adjacent to the building", and where the ground is not level, "the highest part of the surface of the ground next to the building". It also says ground level "would not include any addition laid on top of the ground such as decking". On a sloping garden, ask the council how it applies this to a deck before you build near the line.

Steps, a hot tub and a roof change the answer#

A permit-free deck still needs a way down. At 23 in (584 mm), three risers of 7 2/3 in (195 mm) just fit under the IRC's 7 3/4 in limit. The IRC's stair section exempts only "stairways not within or serving a building, porch or deck", so deck steps are not exempt. Stair dimensions sets out the rise, run and headroom, and the stair rise and run calculator splits any height into equal steps. For steps across the garden beyond the deck, garden path widths and outdoor step dimensions uses a gentler outdoor ratio.

A hot tub changes the load, which none of the permit lines measure. Hot tub dimensions, pad size and clearances gives 95 to 125 lb/ft² (465 to 610 kg/m²) for a filled tub. A deck built to the IRC's 40 lb/ft² live load is not sized for that, permit or not. Edmonton's "heavy loads" test is one place where the rule names it.

A roof changes the answer in every Canadian town compared here. Red Deer and Sudbury require a permit for a covered deck, and Edmonton exempts only decks with no roof or walls. Portland's brochure leaves covered decks out. The roof frame itself has its own rules, covered in pergola dimensions and heights.

A deck on the ground is the cheapest way out of every rule here. Laid as a patio, the same area needs no permit in Red Deer at 9 in or less, and patio sizes and layouts gives the paving sizes for each use.

Where these numbers stop applying#

The figures here are the 2021 IRC model text and the rules of the places named, as each publishes them. A state or town that adopts the IRC can amend the deck item, and Portland and Edmonton show how far that goes. Your own building department's wording decides. A homeowners' association, a deed covenant or a lease can be stricter, and none is covered.

A permit-free deck is not a checked deck. No inspector looks at the footings, the post size, the joist span or the fixings. The code still applies to all of them, and the owner carries the risk. Electrical work for deck lights or a hot tub is outside the building exemption and is not covered here. Zoning setbacks, which apply to a deck of any height, are named only where the sources state them. The page also leaves out Wales, Scotland, Northern Ireland, the rest of Canada and Australia. Whether a deck built tight to the wall but not fixed to it counts as attached is the building official's call.

Metric figures are the sources' own where they print them and conversions otherwise, as imperial and metric dimension systems explains, and the unit converter does the rest. Terms such as guard and grade are defined in the glossary, and the codes behind this page are indexed under standards and codes. The same split between a permit line and a height cap runs through how tall a fence can be without a permit.