Can I add a dormer or extension after buying a house?

Building without a permit under the Environment and Planning Act

The Omgevingswet (Environment and Planning Act) has applied since 1 January 2024. You may build a number of small structures without a permit, provided you stay within the rules of the Besluit bouwwerken leefomgeving (Bbl, the Building Decree). This mainly concerns building at the rear, in the so-called rear yard area (achtererfgebied).

• Dormer at the rear: often permit-free if it stays within set dimensions, for example below the ridge and at a sufficient distance from the edge of the roof. See the rules at IPLO.
• Extension at the rear: in many cases permit-free up to a limited depth and height.
• Outbuilding or shed in the back garden: often permit-free up to a certain floor area, depending on the size of the plot.
• Front and sides facing the public road: a permit is almost always required here.

Permit-free does not mean rule-free: the technical building regulations always apply, and your neighbours' rights still matter.

The omgevingsplan and the bestemmingsplan

In addition to the national rules, every municipality has an omgevingsplan (zoning plan). It sets out, for example, the designated use of a plot, the building envelope (bouwvlak) within which building is allowed and the maximum eaves and building height. Since 2024, old land-use plans (bestemmingsplannen) have been part of that omgevingsplan and therefore still apply.

Outside the permit-free category, the omgevingsplan determines whether a building plan is possible. If your extension falls outside the building envelope or the roof would be higher than permitted, you need an omgevingsvergunning (environmental permit), and it is not always granted.

Listed building or protected townscape

If the property is a national or municipal listed building (rijksmonument or gemeentelijk monument), or lies within a protected townscape or village view (beschermd stads- of dorpsgezicht), stricter rules apply. Building without a permit is then often not possible. Read more in living in a listed building.

How to check in advance

• Use the free permit check in the Omgevingsloket (the government's planning portal) for the address and your building plan.
• Check the designated use, the building envelope and the maximum building height from the land-use plan in the property report, as well as whether the building is listed.
• Ask the seller whether previous renovations had a permit. See looking up permits.
• If in doubt, call the municipality or ask an architect or building consultant to take a look.

This article is a general explanation and not legal advice. For your situation, the rules in the Omgevingsloket and the municipality's omgevingsplan are decisive.