Granny flat: rules and permit

When is a granny annexe permit-free?

Under the Environment Act and the Building Decree (Bbl), a granny annexe in the rear garden area may be permit-free as an associated structure. The granny annexe scheme is not a separate permit category but falls under the broader category of associated structures in the rear garden area, with one additional condition: the use must demonstrably be aimed at providing informal care.

The core of the scheme:

• The unit is located in the rear plot area of the home (behind a line 1 metre behind the front facade, not adjoining publicly accessible land).
• The built-up area stays within the permitted limits for the building area (see below).
• The height stays within the permitted dimensions for ancillary structures.
• There is a genuine need for informal care.

Proof of care need: Most municipalities require a carer's declaration or care assessment to be submitted as proof of the care relationship. This can be a CIZ assessment (Centrum indicatiestelling zorg), a statement from a GP or specialist, or a self-declaration accepted by the municipality. Always check with your municipality in advance what proof is required: the requirements differ per municipality.

Dimensions of accessory structures (qualitative): The rear garden area may only be built on up to a certain percentage. The larger the buildable area, the more you may build, but there is an absolute maximum. A small unit of 20 to 35 m² fits comfortably within the limits on most plots. The maximum height for accessory structures is 5 metres; if the unit is more than 4 metres from the dwelling, additional rules apply regarding height and use. Consult the Omgevingsloket for the exact dimensions at your address.

Always do the permit check: Even if you think the situation is permit-free, do the permit check on the Omgevingsloket (omgevingsloket.nl). The outcome is location-specific and takes into account the environment plan of your municipality. Some municipalities have included additional rules that go beyond the Bbl.

New rules on the way. With the Housing Management Act the government is relaxing the rules for family and care homes on your own plot. The formal care declaration will lapse and the scheme will also apply to parents, children and step- and in-law family. The permit-free variant will be arranged in an amendment of the Buildings Decree that is expected to take effect on 1 January 2027. The technical requirements of the Bbl always continue to apply, even without a permit.

When do you need a permit?

There are several situations in which a granny annexe is not permit-free and you need to apply for an environmental permit.

Larger unit or exceeding the surface area limits: If you want to build a larger living unit than the permit-free dimensions allow, an environmental permit is required for the environment plan activity. The municipality then assesses whether it fits within the environment plan and what restrictions apply.

Location outside the rear garden area: If you place the unit in the front garden area or on the side of the house less than 1 metre behind the front facade, a permit is always required. This also applies to an extension at the front of the house.

Listed building/monument or protected townscape or village scene: Do you live in or near a national monument, a municipal monument, or in a protected townscape or village scene? If so, the permit-free options largely fall away. Every change to or near a national monument requires an environmental permit for the national monument activity.

No demonstrable care relationship: If there is no demonstrable informal care need, the unit does not fall under the granny annexe scheme. A detached outbuilding with sleeping and sanitary facilities used as an independent dwelling is simply not permitted in most environment plans without a permit and deviation procedure.

Municipality that has set additional rules: Some municipalities have included specific rules on granny annexes in their environment plan that deviate from the Bbl. They may prescribe a smaller maximum surface area, impose additional aesthetic review requirements, or grant a temporary permit tied to the duration of the care need.

Multiple activities: For a larger extension or a unit that is technically substantial, the technical building activity may also require a permit. Structural safety must then be demonstrated via a permit application including a structural calculation.

What happens when the care need ceases?

One of the most practical yet most overlooked aspects of a granny annexe is what needs to happen afterwards. The temporary status is tied to the care need.

The care need ends: If the person for whom the granny annexe was built passes away, moves away or no longer needs intensive care, the basis for the granny annexe scheme also ends. The unit then loses its special use status as a 'granny annexe'.

What does that mean in practice? A permit-free unit may not, after the care need has ended, be used as an independent dwelling or for any other use that does not fit the description of an accessory structure in the rear garden area. If you nevertheless use the unit as an independent rental property or for another purpose, you are in violation and the municipality may take enforcement action.

What are your options?

• The unit can be used as an outbuilding, storage or hobby space, provided the use complies with the rules for ancillary structures (no independent residential use, no accommodation).
• You can apply for a building permit to give the unit a different or permanent residential use, if the zoning plan allows it.
• In some cases, the unit must be returned to its original state or given a different use that is either permit-free or covered by a permit.

Some municipalities record the obligation to remove the granny annexe or adjust its status in a private-law agreement or as a condition of the permit. Find out in advance from the municipality what the arrangements are if the care situation changes. This prevents surprises at the moment you least expect them.

Extension to the home or separate outbuilding: what is the difference?

When realising a granny annexe you face a fundamental choice: do you connect the unit to the existing dwelling or build it as a separate structure in the garden? Both options have advantages and disadvantages and they partly follow different rules.

Extension to the existing home: An extension is physically connected to the dwelling. The unit shares a wall with the main property and typically has its own entrance at the rear. Advantages: more energy-efficient due to the shared facade, easier to integrate with the existing services (water, electricity, central heating). Disadvantages: the renovation affects the existing foundation and structure, which always makes a structural calculation necessary. The extension counts towards the built-up area of the rear garden area.

For an extension, the technical construction activity will also quickly require a permit or at least a notification, depending on the scope and complexity. Check this via the Omgevingsloket.

Freestanding outbuilding in the garden: A separate unit offers more privacy for both the carer and the person being cared for. Prefab granny annexes (on a concrete foundation or on piles) are increasingly popular and can sometimes be placed within a few weeks. Structurally they are less invasive for the existing home.

Conditions for a detached outbuilding are stricter if it stands more than 4 metres from the house: it may not then contain habitable rooms on the ground floor that are used as independent living accommodation, unless it has been designated as a granny annexe. The height and floor area are assessed against the Bbl dimensions.

Combination of both: Some situations call for a combination: an extension with its own bedroom and bathroom, but with a shared kitchen. This mostly still falls under the extension rules but the use determines whether it is classified as a granny annexe.

For both an attached extension and a freestanding outbuilding: a construction drawing is always needed to make the dimensions clear for yourself, the contractor and (where a permit is required) the municipality. Tekenpunt delivers these drawings at a level of detail that can be used directly for quotes and construction.

The process: from idea to completed granny annexe

Realising a granny annexe follows a few clear steps. The longer you wait with the preparation, the greater the risk of delay at the moment the care need has already become urgent.

Step 1: Permit check As a first step, carry out the permit check on the Omgevingsloket. Enter your address and the type of structure to find out whether you need an environmental permit for the spatial element and/or the technical element. Save the result for reference.

Step 2: Contact with the municipality Contact the municipality in advance, even if the check indicates that it is permit-free. Ask what evidence of the care need they expect and whether additional rules apply in your environment plan. Also ask about the arrangements when the care need ceases.

Step 3: Have construction drawings made Have a drawing office produce the construction drawings. A good drawing shows the site plan of the plot, the floor plan of the unit, the elevations and a cross-section. For a permit application, an environment plan check sketch and sometimes a layout drawing are also required. Tekenpunt delivers drawings from €595; for an environmental permit application you add the permit service for €500. Delivery time is normally 4 weeks or 1 to 2 weeks with express service.

Step 4: Structural calculation (if required) For an extension attached to the existing dwelling, a structural calculation by a certified structural engineer is always mandatory. For a freestanding prefab unit this depends on the foundation and load-bearing structure. Tekenpunt works with a KIWA-certified structural engineer; a structural calculation costs €700.

Step 5: Submit permit application or start construction For a project that requires a permit, you submit the application via the Omgevingsloket with the drawings and required attachments. The statutory decision period is 8 weeks (single application) with possible extension. For a permit-free project you can go directly to the contractor once the drawings are complete.

Step 6: Construction and completion Preferably record the as-built situation in an as-built drawing in case you want to make changes later or sell the property.

Costs: drawings and additional services

The costs for a granny annexe depend greatly on whether you need a permit, whether a structural calculation is required and how complex the structural situation is. Construction drawings (always): A construction drawing from Tekenpunt starts from €595. The price depends on the size and complexity of the unit: a simple detached unit is priced differently than an extension with multiple floors or a complicated plot situation. Request a quote for your specific situation. Environmental permit (+€500): If you need an environmental permit, Tekenpunt handles the complete application including submission via the Omgevingsloket. The permit service costs €500 on top of the drawing. Tekenpunt gets 90% of applications through the aesthetics review in one go. Structural calculation (+€700): For an extension attached to the existing home or a unit with a more complex load-bearing structure, a structural calculation by a KIWA-certified structural engineer is mandatory. This costs €700. 3D visualization (+€400): Want to visually assess the care annex before hiring a contractor or applying for a permit? A 3D visualization costs €400 and gives you a realistic picture of the result on your plot. If you are in a hurry, expedited delivery is available: +30% for delivery in 2 weeks (minimum €295) or +50% for delivery in 1 week (minimum €495), on top of the regular drawing work. With the expedited service, the delivery time is 1 to 2 weeks instead of the standard 4 weeks. Construction costs (not included): The costs of the contractor and the construction itself are not included. Guide prices for care annexes vary widely: a prefab unit can start at several tens of thousands of euros; a brick-built extension is usually more expensive. Get at least three quotes from contractors in your region. Good drawings are the basis for a fair quote. Tekenpunt is a drafting firm, not an architecture firm. We provide the technical construction and permit drawings; for urban planning advisory reports or complex deviation procedures we refer you to an architect or consultant.

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