Whether you're a smallholder in the UK, a hobby farmer in the US, or a vineyard owner in Australia, understanding how large an outbuilding you can construct without formal planning permission can save time, money, and legal troubles.
In this guide, we’ll cover:
The definition of an "outbuilding"
Key size limitations for different countries
Greenhouse-specific advice
Practical tips for compliance
When you do need to apply for planning permission
An outbuilding is any freestanding structure separate from the main house or dwelling. Common examples include:
Agricultural greenhouses
Garden sheds
Storage barns
Workshops
Carports
Animal shelters
Depending on your country and local jurisdiction, the allowable size and location of these structures can vary greatly.
Let’s look at the specifics by region.
Under the UK Permitted Development Rights, homeowners can build outbuildings like greenhouses, garages, and sheds without planning permission as long as certain conditions are met.
Key limitations:
Height:
Maximum height of 2.5 meters if within 2 meters of a boundary.
Up to 4 meters for a dual-pitched roof if farther from boundaries.
Footprint:
Outbuildings must not cover more than 50% of the land around the original house.
Use:
The structure must be incidental to the enjoyment of the house—like gardening, storage, or hobbies. Not for residential use.
Location:
Not allowed in front of the principal elevation (i.e., not in front of your house).
Greenhouse Tip:
A domestic greenhouse typically falls under permitted development if it complies with the above criteria. But commercial greenhouses may still require permission, especially for large-scale operations.
If your land is classified as agricultural (not residential), different rules apply.
Under Part 6 of the General Permitted Development Order, certain agricultural buildings can be built without planning permission:
For holdings over 5 hectares, you can build up to 1,000 square meters of agricultural buildings.
Height must not exceed 12 meters (or 3 meters within 3 km of an aerodrome).
Notification is still required (called “prior approval”), especially for environmental or access considerations.
In the U.S., there is no federal limit on outbuilding sizes—everything is managed at the state and county level. But here are some general trends:
Typical size limit:
Often up to 200 square feet (18.5 sqm) without a building permit (e.g., 10x20 ft shed).
Height & location rules:
Must be a certain distance from property lines (setbacks).
May not include utilities (e.g., plumbing) without additional permits.
Farmers in agricultural zones often benefit from exemptions:
In states like Texas or Iowa, agricultural buildings (barns, greenhouses) may not require a permit if:
Used strictly for agricultural purposes
Built on land zoned AG (Agriculture)
However, structures with plumbing, HVAC, or electricity may still need separate permits.
Greenhouse Tip:
In states with strong farming economies, like California, Florida, or Georgia, many greenhouses under 1,000–2,000 sqft can be built permit-free—especially if used seasonally.
Each Australian state sets its own rules, but they all recognize certain exempt developments.
Outbuildings (sheds, greenhouses) may not need approval if:
Less than 20 square meters in area
Less than 3 meters in height (or 2.4 meters if within boundary setbacks)
Not built in a heritage or environmental zone
10 sqm limit without a permit
Must not be attached to another building
Must be no higher than 3 meters
For larger rural properties, exemptions may exist for agricultural use buildings if:
They are not for human habitation
They meet safety and fire distance requirements
Greenhouse Tip:
Greenhouses under 20 sqm are often exempt in urban areas. For larger rural greenhouses, contact your local council for a Certificate of Exemption or Fast-Track Permit.
Find out if your land is zoned residential, agricultural, commercial, or mixed-use. This will determine whether your project qualifies as permitted development.
Even if the size is under the limit, the location matters. Most areas require a setback of 1–3 meters from neighboring property lines.
Many permission-free structures are limited to 2.5–4 meters in height. Greenhouses with ridge vents or A-frame structures may exceed this—custom designs may help.
Modular greenhouses (such as ours) can be scaled and split into segments to comply with local regulations, then expanded later under proper permit.
Before starting any large project, it’s always safer to check with your local planning office. They can confirm whether a Certificate of Lawful Development is recommended.
Planning permission is usually required if:
The structure exceeds permitted size or height
It’s built near protected areas (heritage, conservation, national parks)
It includes plumbing or human accommodation
You are running a commercial greenhouse business in a residential zone
In such cases, submitting a full application with architectural plans and environmental impact statements may be necessary.
As a manufacturer of professional-grade agricultural greenhouses, we understand the regulations in different countries and regions.
Our services include:
Custom greenhouse sizes under 20, 50, or 100 sqm for permit-free zones
Modular structures that can expand when approval is granted
Height-customized greenhouse frames to meet roof limits
Planning documents and CAD drawings for permit applications
Guidance on local rules for export clients (UK, US, EU, AUS, etc.)
Understanding how large you can build an outbuilding—such as a greenhouse—without planning permission is essential for efficient and legal property development. While rules vary by region, size limits of 10–20 sqm for residential zones and up to 1,000 sqm for agricultural land are common across many countries.
If you're unsure, our team can help you design a structure that fits your land—and the law.
Need a greenhouse that fits your legal limits?
Contact us today for tailored greenhouse solutions that comply with your local regulations.
+86 189 2488 9901 +86 189 2455 5194
+86 189 2488 9901 +86 189 2455 5194
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