Yes, for most houses in Hertford Heath, within the usual rules. The listed buildings are few, and almost all are in the most ordinary grade. One corner of the village is a conservation area. One patch of ground is protected more strictly than any house. Everyone else is extending, and the planning register is busy.
Hertford Heath has 36 listed buildings: none at Grade I, one at Grade II* and 35 at Grade II. Listing covers the whole building, inside and out, so changing a listed house needs listed building consent from East Hertfordshire Council on top of any planning permission, even for work that would be permitted development on the house next door. If you own one of the 36, the council has a say in your windows, your kitchen and your choice of mortar. If you own any of the others, it has the usual say and no more.
One conservation area falls within the village: Little Amwell, the old separate village to the north that grew into Hertford Heath during the twentieth century. Inside a conservation area, some of the work you could otherwise do without asking needs planning permission, and the council looks harder at anything visible from the street, including side extensions, roof changes and cladding. No extra restrictions on top of that are on record here. East Hertfordshire Council can tell you whether a house falls inside the Little Amwell boundary and whether any further restrictions apply there, and that is the call to make about a particular address. The boundary decides it, and the boundary rarely follows the village's own sense of where Little Amwell begins.
There is one scheduled monument, the Iron Age cemetery on Trinity Road. Scheduling is the strictest protection there is, and it matters mainly to anyone hoping to dig on or beside that ground. Every other back garden in the village is free of it.
The neighbours are certainly not waiting for permission to dream. East Hertfordshire Council logged 557 planning applications in and around Hertford Heath between April 2024 and June 2026, 238 of them in the last twelve months. That counts applications, so it shows how many people asked, and it says nothing about how many were approved. In a village of fewer than a thousand households, that is a lot of drawings, and every one of them is a reminder that the extension you have in mind is probably already being argued about two doors down.
For most of the village, that leaves the ordinary national rules. A house outside the conservation area and off the listed register can usually take a modest rear extension or loft conversion under permitted development, without a full application. Bungalows and terraced houses have their own limits within those rules. Anything bigger, anything on a listed building and much of what is visible in Little Amwell needs consent from East Hertfordshire Council. Whether that consent arrives is a matter for the council's planning officers and the neighbours who comment on your application.
Your freedom to extend in Hertford Heath is middling: open to most houses and closed for the listed few, with Little Amwell in between, which is where most of the paperwork goes.