When do you need a construction drawing for a rear extension?
For many homeowners, a rear extension is the fastest way to enlarge the home without moving. Whether it's a conservatory, utility room, hobby space or extra bedroom: as soon as a new volume is placed against the existing home, the municipality requires a complete set of construction drawings. These drawings form the basis for the environmental permit and give the contractor the information needed to correctly connect the foundation, facade and roof to the existing structure.
Common situations where a rear-extension drawing is needed:
- A rear extension at the back of the home for extra living space.
- A conservatory or garden room with large glass sections against the existing facade.
- A utility room or storage space that relieves the existing functions of the home.
- A care annexe or bedroom with bathroom for family on the ground floor.
What does a rear-extension construction drawing include?
A complete construction drawing for a rear extension contains floor plans of both the existing and the new situation, so the municipality can see at a glance what is changing. The facade views show the extension from the rear and, where relevant, the side facade, with material choice, frame layout and roof type. A cross-section shows the height, roof pitch and connection to the existing home.
On the site plan, the extension is drawn within the plot, with distances to the property boundary and the position of the home relative to the neighbours. For larger extensions or special materials, detail drawings are also added, for example of the foundation, the flat roof or a bend in the facade.
Permits and permit-free building
A rear extension is in many cases subject to a permit, but under strict conditions of depth, height and distance to the property boundary, a rear extension at the back can be carried out permit-free. The national rules are set out in the Buildings (Living Environment) Decree and apply only to the rear-garden area of a home. Important points of attention are the maximum depth relative to the original rear facade, the building height and the surface area of the built-up rear garden.
When in doubt, it always pays to check in advance via the Environment Desk whether the extension is permit-free. Is the extension at the front or side, or does it exceed the national rules? Then an environmental permit is required and the design is assessed against the municipal aesthetic policy by the aesthetic (welstand) committee.
What does a rear-extension construction drawing cost?
A rear-extension construction drawing is available from €400. The final price depends on the size of the extension, the complexity of the connection to the existing home and the availability of a building file or existing drawings. For a simple extension on a standard terraced house, the drawing work is finished faster than for an extension on a corner house with multiple visible facades or a home of an older construction year for which the existing drawings are missing.
Also keep in mind the municipal permit fees, which are calculated as a percentage of the construction cost. For larger extensions, a structural calculation and advice from an installer may also be required.
Difference between a rear extension and an extension
In practice, the terms rear extension (aanbouw) and extension (uitbouw) are used interchangeably, but structurally there is a difference. A rear extension is a separate volume placed against the home, often with its own roof shape and functionally distinct from the existing space. An extension is a continued lengthening of an existing space, for example the living room or kitchen, and usually has the same roof shape as the main building.
Which term you choose makes little difference for the permit; the rules for permit-free building apply to both. The choice can, however, affect the appearance of your home and the aesthetic assessment. During the intake, we discuss which approach suits your home and your wishes.
