When planning a garden annexe, the prospect of navigating planning permission can feel daunting.
However, alongside the traditional planning application process, there is an alternative route that often simplifies the process: obtaining permission under the Caravan Sites Act 1968 (commonly referred to as the Mobile Home Act).
At Henley Garden Buildings, we partner with a specialist planning consultancy that focuses exclusively on garden buildings and annexes.
This collaboration enables us to guide our clients through the Mobile Home Act route with clarity, confidence, and complete legal compliance.
The Mobile Home Act allows certain structures to be classed as “mobile homes” rather than permanent dwellings.
Although the term might suggest something temporary, in reality these buildings can be beautifully designed, high-spec structures, indistinguishable in quality and finish from permanent homes.
Provided a design meets the legal definition of a mobile home, this route can streamline the planning process and offer a faster, more cost-effective way of achieving your new space. In some circumstances, however, a full planning application may still be required — and, as with all planning matters, approvals are never guaranteed.
Our role is to make the process as straightforward and stress-free as possible.
To meet the legal definition of a mobile home under the Caravan Sites Act 1968, your garden building must adhere to the following:
External dimensions must not exceed 20m in length, 6.8m in width, and 3.05m in internal ceiling height.
The building must be formed as a single unit, either constructed in one piece or delivered in two sections that are joined on site.
The building must be theoretically capable of being moved, even if there is no intention to move it. The structure should not be permanently affixed to the ground.
The building must remain ancillary to the main house, for example, as a family annexe or garden retreat and not be sold or rented as a separate dwelling.
It must be sited within the curtilage of the existing home (typically your garden or domestic grounds).
A Certificate of Lawfulness is usually submitted to the local authority to confirm that your proposal meets these definitions. We manage this entire process on your behalf through our specialist planning partner.
We offer a fully managed planning route for our garden annexes and retreats, working alongside a trusted planning consultancy with in-depth experience in this specialist area. Together, we ensure your project is legally compliant, technically sound, and beautifully executed.
Our process includes:
While this route provides an excellent solution for many homeowners, we always recommend a site-specific review.
Properties in conservation areas, on agricultural land, or with restrictive covenants may require additional planning input. That’s why we begin with a comprehensive assessment, giving you a clear understanding of what’s possible before any commitment is made.
It’s also important to note that, despite the term “mobile home,” the final building is anything but temporary in feel. Our structures are architecturally elegant, expertly constructed, and finished to an exceptional standard, fully insulated, equipped with integrated services, and tailored to your lifestyle.
At Henley Garden Buildings, we combine meticulous design with a truly turnkey service. Every annexe or retreat we create is crafted with purpose and personality, whether it proceeds via the Caravan Act or traditional planning. We provide:
With a trusted planning partner and decades of combined design and construction expertise, we make the process feel simple — while delivering something truly exceptional.
If you’re considering a garden annexe or retreat and would like to explore whether the Mobile Home Act route is right for you, we’d be delighted to help.
