Garden Office Planning Permission in Dorset: 2026 Guide

Every week someone asks us the same question about garden offices: do I need planning permission? Nine times out of ten the answer is no, and that surprises people. But the tenth case is exactly the one that ends up with a council letter or an awkward conversation over the fence, so it's worth five minutes to check before you order anything.

We've built garden offices, gyms and studios across Dorset and Hampshire, from a 14m² office in Fareham to studios squeezed behind Victorian terraces in Poole. Here's how the rules actually work in 2026, where local quirks trip people up, and what the whole thing costs. The good news up front: most of the time you can be in and working within a month of the base going down.

Most garden offices don't need planning permission

Garden buildings fall under permitted development as long as they're 'incidental' to the main house. A home office, gym or studio counts; sleeping accommodation doesn't. To stay inside permitted development, your building needs to tick every one of these boxes:

• Single storey, with eaves no higher than 2.5 metres.

• If any part sits within 2 metres of a boundary, the whole building must stay under 2.5 metres tall. That's why most garden offices have flat or gently sloping roofs.

• More than 2 metres from every boundary, you can go up to 4 metres with a dual-pitched roof, or 3 metres otherwise.

• No verandas, balconies or raised platforms.

• It can't sit forward of the front wall of the house.

• Outbuildings can't cover more than half the land around the house.

One thing catches people constantly: that height is measured from the highest natural ground level beside the building. On a sloping plot, and Dorset has plenty, you can lose 300mm of headroom before you've laid a single block. We check levels on every survey for exactly this reason.

Where Dorset catches people out

Permitted development shrinks on what planners call designated land, and we have a lot of it round here. In a conservation area, the middle of Wimborne say, or parts of Poole Old Town, you can't put an outbuilding at the side of the house without an application. Across the Dorset National Landscape and the New Forest National Park, any garden building more than 20 metres from the house is capped at 10m² of floor area. And if the house is listed, everything needs consent, full stop.

Use matters too. Working from your garden office is fine. Running a business with staff or clients coming and going every day can tip you into needing permission, and so does turning it into an annexe someone sleeps in. If you're anywhere near one of these lines, don't guess. A wrong assumption is cheap to check now and expensive to unpick later.

Building regulations are a separate question

Planning permission and building regulations are different approvals handled by different departments, and people mix them up all the time. Even when planning isn't needed, building regs can be. Under 15m² of floor area with no sleeping in it, you're generally exempt. Between 15m² and 30m², you're still exempt if the building sits at least a metre from the boundary or is built substantially from non-combustible materials. The electrics are the exception: any new circuit run to a garden building is notifiable under Part P wherever it sits, which is why our own electricians wire and certify every office we build rather than leaving you to sort it afterwards.

What it costs in 2026

If you do need to apply, a householder planning application in England costs £548 from April 2026, paid to the council. If you're inside permitted development but want it in writing, sensible if you might sell within a few years, a lawful development certificate costs £274 and gives you a formal decision to show a buyer's solicitor.

As for the build itself, most of the fully insulated, wired offices we put up come in around £1,800 to £2,600 per square metre depending on spec, so a typical 12m² office lands between £22,000 and £30,000 all in, with three to four weeks on site once the base goes down.

What moves the number? Distance from the house for the power run, ground conditions for the base, and glazing. A level lawn ten metres from the consumer unit is the cheap end. A sloping plot at the bottom of a long garden isn't.

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Not sure which side of the line your garden falls?

Send us a photo of the spot and a rough idea of what you're after, and we'll tell you straight whether it needs an application, before you've spent a penny. Book a free site survey and we'll walk the plot, check the boundaries and levels, and give you a fixed quote for the whole job, planning included if it needs it.