How big can a shed be without a permit?

A one-storey shed standing apart from a US house can have 200 sq ft (18.6 m²) of floor area without a building permit. That is the International Residential Code. The International Building Code, written for every other kind of building, says 120 sq ft (11.1 m²). England, Wales and Ontario set 15 m² (161 sq ft). Scotland sets 8 m² (86 sq ft). These figures lift the building permit and nothing else. Height and distance from the fence are zoning rules in the US and planning rules in the UK, and they apply at any size. Below, the eight rulebooks sit side by side, as the rest of outdoor room dimensions does for patios and decks.

What "without a permit" means: two kinds of permission#

Two different permissions get called "a permit", and mixing them up causes most of the confusion.

A building permit is approval from the building department. It says the structure meets the building code: it will stand up, resist fire and be safe to use. In Scotland the same thing is called a building warrant. In England and Wales it is building regulations approval. The size limits in this article are exemptions from this permission.

Planning permission or a zoning permit decides where a building may go and how big it may be on the lot. It covers setbacks from the property line, height and how much of the yard may be built on. In England the shed rules for planning are called permitted development: work the law allows without an application, within set limits.

An accessory structure is the code's word for a building that serves the house but is not part of it: a shed, a playhouse, a detached garage. Floor area is the floor the walls enclose, not the roof overhang. None of the sources quoted here says whether to measure to the inside or outside of the walls, so near a limit, ask the building department.

The two permissions are tested separately. A shed can need no building permit and still break a zoning rule. Both model US codes say so in the same section: 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 or any other laws or ordinances".

120 or 200 sq ft: both are real, and the code your town adopted decides#

Section R105.2 of the 2021 IRC lists the work that needs no permit. First on the list: "one-story detached accessory structures, provided that the floor area does not exceed 200 square feet (18.58 m2)". Storm shelters are excluded. The IRC covers one- and two-family houses and townhouses, so this is the rule for most garden sheds.

Section 105.2 of the 2021 IBC has the same item at a smaller size: "one-story detached accessory structures used as tool and storage sheds, playhouses and similar uses, provided that the floor area is not greater than 120 square feet (11 m2)". The IBC covers everything the IRC does not. The 120 figure circulates because it is the IBC's, and because many towns and shed sellers quote it.

Neither code is law until a state or town adopts it, and adopters change the numbers:

• Connecticut adopts the IBC but amends the item to 200 square feet, so the two codes agree there.
• Washington County, Oregon allows 200 sq ft for a non-habitable, one-storey shed, and adds a height limit of 15 ft (4.57 m). The height runs "from grade plane to the average height of the highest roof surface", which the county says is "typically the distance half-way between the top of the wall and the peak of the roof". On a lot of 2 acres or more, a shed 20 ft (6.1 m) from every property line and building can be 400 sq ft (37.2 m²).
• Mebane, North Carolina uses a length, not an area. A shed that does not exceed 12 ft (3.66 m) "in any dimension" needs no building permit, the city's permit FAQ says, "but will still require a zoning permit". The largest floor that passes is 12 x 12 ft, 144 sq ft (13.4 m²).

The model codes set no height beyond "one-story". Any height limit comes from the adopter or local zoning.

The same two sheds under eight rulebooks#

Take two common shed sizes and walk them through each rule. A 10 x 12 ft shed is 120 sq ft (11.1 m²). A 12 x 16 ft shed is 192 sq ft (17.8 m²). Both are one storey and used for storage, with no water or power.

The 12 x 16 ft shed is the useful test: it passes in Oregon and NSW and fails in Mebane and Ontario. In England, placing it decides it.

England and Wales: 15 m² is the building rule, 2.5 m is the planning rule#

Two separate laws apply to a garden shed in England, and they measure different things.

The Building Regulations 2010 exempt small detached buildings in Schedule 2, Class 6. A detached building with a floor area of no more than 15 m² (161 sq ft) is exempt if it "contains no sleeping accommodation". A detached single-storey building of up to 30 m² (323 sq ft) is exempt too, on two conditions. It must have no sleeping accommodation, and either "no point of which is less than one metre from the boundary of its curtilage", or it is "constructed substantially of non-combustible material". The curtilage is the land that goes with the house: the garden. The same schedule applies in Wales.

The planning rules are Class E of the General Permitted Development (England) Order 2015. Class E sets no floor area for a single shed. It limits height and position instead, as the setbacks table below lists: 2.5 m (8 ft 2 in) within 2 m (6 ft 7 in) of the boundary, 3 m (9 ft 10 in) elsewhere or 4 m (13 ft 1 in) with a dual-pitched roof, eaves 2.5 m, one storey. Nothing may sit forward of the front wall of the original house, and outbuildings may cover no more than half the garden. In a national park, an area of outstanding natural beauty, the Broads or a World Heritage Site, buildings over 20 m (66 ft) from the house may cover 10 m² (108 sq ft) in total.

So the 12 x 16 ft shed, at 17.8 m², needs no planning application if it stays under the height limits. For building regulations it is over 15 m², so a timber shed must stand at least 1 m (3 ft 3 in) from every boundary. A metal shed can go closer, if it counts as "substantially" non-combustible. The Regulations give no test for that word. On the boundary, the timber version needs building regulations approval.

The two lines on the plan below make three bands. Against the fence, up to 1 m in, a timber shed must be 15 m² or less and 2.5 m high. From 1 m to 2 m it may be 30 m², still 2.5 m high. Past 2 m the height allowance rises to 3 m, or 4 m with a pitched roof.

Wales follows the same planning pattern, with one extra limit. Its outbuildings guidance says any part within 2 m of the house "cannot exceed a height of 1.5 metres", and a flat-roofed outbuilding may not exceed 2.5 m anywhere. Otherwise the limit is 3 m for a single pitch and 4 m for more than one. The same limits caught the garden frame in how tall a pergola should be, which councils treat as a Class E outbuilding.

Scotland: 8 m² exempt, 30 m² without a warrant#

The Building (Scotland) Regulations 2004 split the rule in two. Schedule 1, type 17, exempts a detached single-storey building ancillary to a house entirely, unless it exceeds 8 m² (86 sq ft). Schedule 3, type 4, covers 8 to 30 m² (86 to 323 sq ft). Those need no warrant, but only "on condition" that they meet the building standards: nobody checks in advance, yet the shed must comply.

Both exclude "a building within 1 metre of the house unless it is at least 1 metre from any boundary", and any building with a fixed combustion appliance or sanitary facility.

Scottish planning is Class 3A of the 1992 Order. A building may be 4 m (13 ft 1 in) high with eaves up to 3 m (9 ft 10 in). Within 1 m (3 ft 3 in) of the boundary it may not exceed 2.5 m (8 ft 2 in). The line sits 1 m from the fence, not 2 m as in England. In a conservation area the footprint may not exceed 8 m², and within the grounds of a listed building 4 m² (43 sq ft).

Ontario and New South Wales: 15 m² and 20 m²#

Ontario amended its Building Code to exempt small sheds. The City of Ottawa's December 2025 advisory quotes the rule, Division C, Part 1, Sentence 1.3.1.1.(6). A shed is exempt if it is "not more than 15m2 in gross area, not more than 1 storey in height, not attached to any other building on the lot, does not contain any plumbing and is used only for storage purposes". Ottawa's own position extends it to gazebos and pergolas of that size, and the advisory adds that the zoning by-law still governs where they go.

New South Wales combines planning and building in one test, called exempt development. If a shed meets the standards in clauses 2.17 and 2.18 of the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008, the state's fact sheet says "you do not need planning or building approval". Armidale Regional Council's summary of the standards gives the main figures:

• 20 m² (215 sq ft) in most zones;
• 50 m² (538 sq ft) in rural zones RU1 to RU6 and large-lot residential R5;
• no higher than 3 m (9 ft 10 in) above existing ground;
• 900 mm (35 in) from boundaries, or 5 m (16 ft 5 in) in rural zones.

The fact sheet adds that a shed on bushfire-prone land must be built of non-combustible materials. Other Australian states have their own rules, not covered here.

Setbacks and height: the rules that apply at any size#

The rules that decide where a shed may stand apply at any size. In the US they are local.

In the UK a planning height is measured from the ground beside the building, and on a slope from its highest part. The English guidance adds that ground level does not include decking laid on top, so a shed on a raised base loses that height from its allowance. Raised platforms over 300 mm (11.8 in) fall outside Class E, the limit that also governs deck sizes and railing heights in a garden.

A shed is a structure for the fire code too: an open wood fire must be 25 ft (7.6 m) from it, per fire pit clearances and seating.

What a 200 sq ft shed holds, and how to lay it out#

A shed at the US limit is smaller than a garage. The site's garage sizes page puts the smallest useful single garage at 12 x 22 ft (3.7 x 6.7 m), or 264 sq ft. A 200 sq ft shed can be 10 x 20 ft (3.05 x 6.10 m) or 12 x 16 ft with 8 sq ft spare. Neither takes a car.

Ripping a 4 x 8 ft sheet on a table saw needs 18 ft 6 in (5.6 m) of clear line, per workshop tool clearances, so only the 10 x 20 ft shape works as a saw shop. Hung by the front wheel, a bike takes 16 in (41 cm) of wall in bike and sports storage, so a 12 ft wall holds nine.

Plan the route to the door as well: a main garden path is 48 in (1,220 mm) wide in garden path widths and outdoor step dimensions. Patio sizes and layouts covers the paving around it, and taping out a layout at full size shows how to mark the footprint before you order. Watch imported sizes: a US 200 sq ft kit is 18.6 m², over the 15 m² line in England. Figures here are converted, not rounded, for the reasons in imperial and metric dimension systems, and the unit converter does the rest.

Where these numbers stop applying#

Every figure above exempts a shed for storage or play. A shed used to sleep, live or work in is a different building in every rulebook here. Washington County puts it plainly: "If it is habitable, it needs a permit."

The exemptions cover the building work only. A shed with electricity, water or a heater may need its own permit even when the building needs none; Mebane says an electrical permit "may be required". A shed attached to the house falls outside the US, UK and Ontario exemptions, which all require it to be detached. In England it falls under the rules for extensions.

The UK permitted development rights belong to houses. Flats, maisonettes and listed buildings need an application, and a council can remove the rights with an Article 4 direction or a planning condition. Northern Ireland, other Canadian provinces, other Australian states and US places not named here are not covered. Nor are deed covenants or leases. The US figures are the 2021 editions as adopted where named.

Standards and codes lists the codes the site draws on, and the glossary defines curtilage and eaves.