It is the first question we are asked on most first visits, and the honest answer is: usually no — but the exceptions matter, and they matter more in this part of the world than almost anywhere else.
Most pergolas, garden rooms, terraces and walls in ordinary Hertfordshire gardens fall within permitted development — the national grants that let you build certain things without a planning application. The rules have limits though, and the limits are where projects quietly come unstuck.
Take garden buildings. A garden room or summerhouse is generally permitted development if it sits behind the house rather than in front, covers no more than half the curtilage, and keeps to the height rules: 2.5 metres at the eaves if it is within two metres of a boundary, 3 metres flat-roofed or 4 metres with a dual-pitch roof elsewhere. It must also be genuinely incidental — an office, a studio, a gym — not self-contained living accommodation. Cross any one of those lines and you are into a planning application.
Walls and fences have their own arithmetic: under one metre high beside a highway, under two metres elsewhere, and you are within permitted development. Above those heights, permission is needed — and in Hertfordshire, where boundaries often carry the character of a street, councils look closely.
Patios are the one people do not expect. At the back of the house, a terrace is almost always fine. But since 2008, if you pave more than five square metres of a front garden with an impermeable surface, and the water runs onto the highway, you need planning permission — unless the surface is permeable or the water is drained within the property. It is the reason our driveways and front gardens are built permeable by default, not by exception.
Raised timber decking also counts: if the platform stands more than 300 millimetres above ground level, it leaves permitted development. And a pergola attached to the house is treated as an extension of it rather than a free-standing structure, which tightens the rules.
Then come the three local caveats that change everything.
First: conservation areas. Much of the county's historic stock lies within them — the town centre of Bishop's Stortford, the medieval streets of Saffron Walden, old Harlow around Churchgate Street. Inside a conservation area, permitted development rights are narrowed: cladding is off the menu, outbuildings must sit to the rear, and many councils have removed rights further under what are called Article 4 directions. What is permitted elsewhere needs an application here.
Second: listed buildings. If your house is listed — and hundreds of Hertfordshire houses are — any structure within its curtilage, attached or not, can require listed building consent as well as planning permission. This is a separate consent with a separate process, and building without it is a criminal offence rather than a paperwork error.
Third: local design codes. In Welwyn Garden City, the original Garden City design guide still governs what boundary treatments, materials and front garden changes are acceptable. Epping's Green Belt edge places stricter tests on outbuildings. The practical rule: the constraints of your address, not the national rules alone, decide what you can build.
So how do we handle it? At design stage, before anything is drawn in detail, we check your address against the local plan, any conservation or Article 4 designations, and the listed buildings register — and where consent is needed, we prepare the application as part of the project. Our garden structures are designed to the rules first and to your taste second, which sounds restrictive and is in fact the opposite: the scheme that passes is the scheme that gets built.
If you want to check a specific structure yourself, the national rules are set out at the government's Planning Portal, which also hosts the applications. But for a real answer about a real garden, a first visit costs nothing — and it is cheaper than finding out at application stage.
One last thing: even where permission is not needed, building consent is not the same as building well. A pergola within permitted development still needs proper foundations. A garden room under the height limits still needs certified electrics. The rules tell you what you may build; a good builder decides what will last.