Can a garden home affect the WOZ value of your property?

Yes. A garden home (mantelzorgwoning) that stands permanently on your plot is included when your property is valued. As a result, the WOZ value (the municipal property valuation) can rise, and because that value is the basis for the municipal property tax (onroerendezaakbelasting, OZB), the tax assessment rises with it.

How much that comes to depends on your municipality and on the home. What you can know in advance is which charges may be added and which question makes the biggest difference: does the municipality regard the home as part of your house, or as a separate property.

Part of your house or a property in its own right

The Wet WOZ (the Valuation of Immovable Property Act) provides that a part of a property which, judging by its layout, is intended to be used as a separate unit can be defined separately. A garden home with its own front door, its own kitchen and its own bathroom fits that description.

That leads to two possible outcomes, and you will notice the difference in the tax assessment.

Which way it goes differs per municipality and per situation. So it is not a detail for later: ask your municipality's tax department before the home is in place, not when the assessment lands on your doormat.

What the OZB means in concrete terms

The municipal property tax on homes is levied on the owner, as a percentage of the WOZ value. Your municipality sets that percentage itself every year, and it differs considerably between municipalities. For that reason we do not give an amount here: the same house with the same value costs many times more in one municipality than in another.

What you can do is work it out yourself. Look up the rate for homes in your municipality's tax bylaw, take the expected increase in value and multiply. Then you have a realistic amount instead of a guess, and it is a cost that comes back every year for as long as the home is there.

How the valuation works

The WOZ value is set every year based on the situation on a valuation reference date, which for the current tax year falls in the previous year. A home that is installed in March therefore does not end up in that year's assessment straight away but in the following year's.

The municipality usually values homes by comparing them with homes sold in the area. An outbuilding used as a home is harder to place in that comparison than a shed, and the value assigned to it is an estimate. That is exactly the reason to check the decision rather than filing it away.

When a second household arises

Besides the OZB, every municipality has charges that do not depend on value but on use: the waste collection charge (afvalstoffenheffing) and the sewerage charge (rioolheffing). These are levied per household or per connection, and that is where the question lies.

If the garden home is connected to the existing utilities of your main house, in most municipalities it remains one connection and little changes. If the home gets its own connection, or the resident registers at their own address, a second assessment may follow. That last step is not only a cost but also a choice with other consequences, because a separate address in the Personal Records Database (basisregistratie personen) affects post, insurance and allowances (toeslagen).

This is arranged differently in each municipality, and one phone call makes it clear. Ask the question in concrete terms: will this home get its own assessment for waste and sewerage, and does anything change if the resident registers at this address.

How to lodge an objection

Every WOZ decision is a decision you can object to, within six weeks of the date on it. That is free and can be done without an intermediary. In this situation, four points are worth checking.

• How the property is defined. Has the home rightly or wrongly been designated as a separate property.
• The floor area the municipality uses. Living area and building footprint are regularly mixed up.
• The comparable properties in the valuation card (taxatiekaart). Ask for them; you are entitled to them.
• The special nature of the home. A movable home linked to a temporary care situation is something different from a permanent extension.

What it does to your tax return

If the home belongs to your own home for tax purposes, a higher WOZ value feeds through into the eigenwoningforfait (the notional rental value added to your income), and that increases your taxable income in box 1. If the home does not fall under that, it counts as an asset in box 3 (the tax on savings and investments). Which of the two applies to you is a question for your adviser; the considerations are set out in are the costs tax-deductible.

Also watch out for the knock-on effect on income-related schemes. Higher assets or a higher income can affect allowances and personal contributions for care. What that means is explained in does buying one affect allowances.

A worked example

Suppose you place a home of 46 m² in the garden and the municipality includes it with your own house. The WOZ value then rises by an amount that the valuer assigns to an outbuilding used as a home.

For the OZB, that feeds through via your municipality's rate. If that rate is one tenth of a per cent of the value, every ten thousand euros of extra value costs you ten euros a year; if it is two tenths of a per cent, twice that. It seems little, and per year it is. Over the ten years that such a home is often in place, it adds up to an amount you would rather have seen beforehand than afterwards.

On top of that comes the water board charge, which also depends on value, and the possible second assessment for waste and sewerage. So do not calculate with the purchase price alone but include the annual costs, and put the energy and maintenance costs of the home alongside them. Then you have the real sum.

Does it also increase the sale value of your house

That is not the same as the WOZ value, and the answer is less clear-cut. For a buyer with the same need, a second self-contained living space is worth a lot. For a buyer without that need, it is a building in the garden that needs maintenance and takes up garden space.

That is one of the reasons we buy back our own homes when the care stops. You are then not dependent on whether the next buyer happens to have an informal care situation too. What a home is still worth after years of use is explained in how much residual value a garden home has.

What is best arranged in advance

• Notify your municipality and ask how they will define the home as a property. Ask for a written answer.
• Ask about the charges for waste and sewerage when there is a second household on the same plot.
• Notify your buildings insurer. An unreported home in the garden is a problem when there is damage.
• Include the annual costs in your sum, alongside the energy and maintenance costs of the home itself.

Once you know what you will face financially, do the permit check for your address and put what a garden home costs alongside it. The purchase is a one-off; the municipal charges come back every year, and it is better if you saw them coming.

Sources

• [Act] Wet waardering onroerende zaken — art. 16 (defining the property) and art. 17 (valuation) — accessed 2026-08-20
• [Act] Gemeentewet — art. 220 onwards — the municipal property taxes — accessed 2026-08-20
• [Act] Algemene wet inzake rijksbelastingen — objection period of six weeks — accessed 2026-08-20
• [Act] Wet inkomstenbelasting 2001 — eigenwoningforfait and box 3 — accessed 2026-08-20