When is an extension permit-free?

Building without a permit saves you an application, waiting time and council fees, so it is almost always the first question I get when someone wants to extend. The honest answer is that nobody can answer that question without your plot in front of them. Permit-free is not a property of an extension, it is the outcome of a row of conditions that all have to be right at the same time. If one of them fails, the whole build needs a permit.

Below is the principle and the dials it hangs on, deliberately without measurements in metres. Those numbers have shifted over recent years and work out differently from one situation to the next, and a half-remembered measurement costs people money. So look at the date above this article as well. If it is old, assume something may have changed. What applies to your address today comes from the Omgevingsloket and from your council. Those two have the last word, this piece does not.

Permit-free is not rule-free

Permit-free means you do not have to apply for a permit beforehand. It does not mean the building rules stop applying. The structure has to be right, the join with the existing house has to be watertight, it has to be insulated and ventilated, and fire safety towards the neighbours stays a requirement. There is just nobody coming round to check that beforehand, so the risk sits with you. If it goes wrong later, there is no approved drawing to point at.

Since the Omgevingswet came in, the question also falls into two parts. Is it allowed here, according to your council’s omgevingsplan. And is it allowed like this, according to the technical building rules. Something can be fine without a permit in planning terms and still need a notification technically, so one green tick is not the whole story.

The achtererfgebied is the starting point

Almost all permit-free building happens in what is called the achtererfgebied. Roughly, that is the part of your plot behind the front of your house, away from the public road. The back garden of a terraced house is the textbook example.

At the front, extending is rarely permit-free, because the front facade sets the look of the street and councils are stricter about that. On a corner house it is trickier than people expect: the side that borders the street or public greenery often does not count as achtererfgebied. Two houses in the same row can get a different answer, purely because one of them stands on the corner.

What decides whether it is permit-free

Where on the plot you build

The position relative to the house, the plot boundary and public land is the first sieve. If the spot falls outside the achtererfgebied, the sums usually stop right there.

How deep the extension gets

The depth from the original rear facade is the dial an extension trips over most often. The important word in there is original. If a previous owner has already extended the house to the rear, you are not starting from zero, even though the existing rear wall feels like the starting point.

How high it gets

Height counts twice: the height of the new space itself, and the height of the join with the existing house. A flat roof that stays low gives you more room inside the rules than a roof that comes up against the first floor or the pitch. If you want daylight from above, you are quickly into a different story, a sunroom or a skylight for instance, and the join with the existing roof changes as well. Keeping that watertight is part of the roofing work.

How much is already built

A plot has only a limited amount of space you are allowed to fill, and everything already standing counts towards it. A shed, a canopy, a garden house, an annexe built earlier. This is the one people forget most often, because they look at their empty patch of grass and not at the total. So sometimes the question is not whether you can extend, but what you are willing to give up for it. Pulling down an old shed regularly makes it possible after all.

What the new space is for

It matters what is going to happen in what you build. An extended living room, a store room and a self-contained living space for someone else are not treated the same. As soon as someone is going to live there independently or it gets rented out, the question changes and you have to put that forward separately.

A conservation area or a listed building

This is the exception that can push all the other considerations aside. If your house stands in a protected townscape or village view, or the building is a national, provincial or municipal listed building, the room to build permit-free is much smaller and sometimes nil. That goes for the look on the outside too, so for the choice of materials and for the facade finish. If you are not sure whether your house falls under it, find that out first. It is the cheapest check there is.

What people overlook

Permit-free says nothing about permission from other people. If you live in a block with an owners’ association, you still need that association. If you build against the plot boundary, neighbour law and agreements about the party wall come into play, and those are separate from the council. The Land Registry boundary, by the way, does not automatically run where the fence stands.

Watch the water as well. The ground that soaks up rain now becomes roof, and that water has to go somewhere, not onto the neighbours’ plot. Councils are setting requirements on that more and more often, so ask about it before you design the roof.

How to check it yourself

Start at the Omgevingsloket. There is a permit check there where you fill in your plan and your address and it walks you through the questions step by step. Look at your council’s omgevingsplan as well, because that is where the local rules sit and they differ per area.

If you cannot work it out, or the outcome looks too good, ring the council. Most have a desk or a walk-in hour for building plans. Ask for written confirmation and keep it. A quarter of an hour on the phone is the cheapest step in the whole process, and the council simply has the last word here.

What I do and do not do in this

I am a builder, not a planning officer and not a lawyer. What I do is measure up, map out the existing situation and go through with you which choices make a permit more or less likely. There is often room in the design: less deep, a lower roof or a different spot on the plot can be the difference between applying and not. I would rather have that conversation before you have an extension or an annexe drawn up than after.

If a permit turns out to be needed, that is usually no reason to scrap the plan. I supply the building case and bring in a structural engineer for a structural change. The application itself you submit as the owner.

What such a plan looks like in practice, from foundation to finish, is on the page about extensions and annexes. If the work gets wider, I plan it as a complete renovation in one go. Still in doubt, send me your situation and a few photos through the contact form, and I will have a look before you apply for anything.