The Planning Loophole That Allows Sleeping Accommodation in Outbuildings (When Built in Transportable Sections)
In the world of UK planning law, few topics generate as much interest—and confusion—as the rules governing outbuildings and garden structures, especially those intended for sleeping. A common belief is that you can’t use outbuildings for overnight accommodation without full planning permission. Yet, there’s a little-known and often misunderstood planning loophole that may allow such usage—if the structure is built in transportable sections.
So what is this loophole, how does it work, and what should you be aware of before building a “sleepable” garden room or annex?
What the Law Typically Says About Sleeping in Outbuildings
Under Permitted Development (PD) rights in England (outlined in the Town and Country Planning (General Permitted Development) (England) Order 2015), you can build certain types of outbuildings in your garden without planning permission, subject to size, height, and placement restrictions. However, there’s a major limitation:
Outbuildings under PD cannot be used as “separate, self-contained living accommodation.”
That means you can’t just build a cabin in your garden and start using it like a flat or Airbnb unit—not without going through planning.
But there’s a twist…
The Transportable Section Loophole: A Grey Area
The loophole arises from a combination of planning law and case law that distinguishes between:
• Permanent buildings that require planning permission, and
• Mobile homes or caravans, which may not be considered development at all (and therefore not subject to planning in the same way), provided they are used incidentally to the main house.
This is where Section 29 of the Caravan Sites and Control of Development Act 1960 and the Caravan Sites Act 1968 come in. These laws define a “caravan” as a structure that:
• Is designed or adapted for human habitation,
• Is capable of being moved (either as a whole or in sections), and
• Does not exceed certain size limits (20m x 6.8m and 3.05m in height for twin-unit caravans).
Under this definition, a prefabricated or modular outbuilding that arrives or is assembled in transportable sections—even if installed on your property—can technically qualify as a caravan.
And here’s the key part: If a structure meets the legal definition of a caravan, it does not constitute “operational development”. As a result, planning permission may not be required, as long as the caravan is sited within the residential curtilage and used in a manner incidental to the main dwelling.
Can You Sleep in It? Yes, With Conditions
So yes—you can sleep in such an outbuilding if:
• The structure meets the caravan criteria,
• It is used by members of the household or guests (not as a separate residence),
• It is not rented out as a permanent residence or commercial holiday let, and
• It is sited within the curtilage of your home.
This means your garden “sleep pod” or modular guest lodge can legally include:
• A bed or sleeping area
• A small bathroom
• Even a kitchenette (depending on council views)
As long as it’s for incidental use.
But using it as an independent residence—like housing someone on a long-term basis with a separate utility account or postal address—can still trigger the need for full planning permission.
Key Design Criteria: What Makes a Building ‘Transportable’?
To qualify under the legal definition of a caravan, your structure must:
1. Be capable of being transported (as a whole or in sections)
2. Be assembled from no more than two sections delivered separately
3. Remain physically movable (i.e., not permanently affixed to foundations)
4. Fall within maximum dimensions of:
• 20 metres long
• 6.8 metres wide
• 3.05 metres in internal height (excluding chassis)
This is why many companies now build “garden lodges,” “granny annexes,” or “mobile homes” in pre-fabricated twin units, delivered and installed on-site—then marketed as planning-exempt under this caravan definition.
Relevant Case Law and Precedents
Several planning appeals and tribunal cases have tested the waters on this issue, confirming the legality in certain cases:
• Brighton & Hove Council v. Secretary of State (2001): Confirmed that a mobile home within curtilage, used for incidental purposes, did not require planning permission.
• Measor v. Secretary of State (1999): Reaffirmed the difference between a use of land for stationing a caravan and the erection of a building requiring planning.
The Planning Inspectorate has also approved various Certificate of Lawfulness applications for garden lodges used for family or incidental sleeping purposes, provided they qualify as caravans.
Caveats and Risks
Before you go ahead with a garden lodge for sleeping use, be aware of the following:
1. You May Still Need a Certificate of Lawfulness
This is a legal document that confirms your proposal is within permitted rights. It’s optional—but strongly recommended.
2. Use Must Remain Incidental
If someone lives in the structure permanently and independently, you risk enforcement action.
3. Local Authority Discretion
Some councils take a stricter view of what “incidental use” means—especially where bathroom/kitchen facilities are involved.
4. No Business Use Without Planning
You can’t rent the unit on Airbnb or host lodgers for income without planning permission.
Best Practices for Staying Within the Loophole
1. Use a professional supplier who understands transportable construction and planning nuances.
2. Keep foundations minimal or temporary—e.g., plinths, pads, or jack legs.
3. Don’t connect the unit to separate utilities—shared supplies are less likely to trigger enforcement.
4. Apply for a Certificate of Lawfulness for peace of mind.
5. Keep documentation showing that the structure was delivered in transportable sections and could be removed.
Conclusion: Legal, But With Limits
The idea that “you can’t have a bedroom in your garden” isn’t quite true. Thanks to a legal quirk that treats certain transportable structures as caravans, you may be able to install a sleepable outbuilding without full planning permission—so long as it’s built in transportable sections and used in an incidental manner.
But this is a legal grey area and not without risk. If you’re considering this route, get professional advice, keep your documentation, and consider applying for a Certificate of Lawfulness to future-proof your project.
Disclaimer: This article is for general informational purposes only and does not constitute legal or professional advice. Always consult relevant professionals and local authorities before undertaking any development or change of use.