Building an Extension: Permits, Process, and Costs in 2025

An extension is not just a construction project, but also an investment in comfort and quality of life. However, building an extension is not a simple process. You need to take various steps into account, such as applying for the right permits, drawing up a detailed plan for the construction process, and carefully managing the costs.

This guide tells you everything you need to know to make your extension a success.

What exactly is an extension?

An extension is an extra space that you add to your existing home. It can be built on the side, back, or even the front of your house. The possibilities range from a simple conservatory to a large extension with multiple rooms, depending on your plot, budget, and living requirements.

Unlike a superstructure, where you add a floor on top of the existing house, an extension adds extra space horizontally. This often makes it technically simpler and, in many cases, more attractive to municipalities when granting permits. Moreover, in many situations, it is a less drastic renovation than a superstructure, which means less disruption for residents and neighbors.

Advantages of an extension

An extension offers many advantages. You increase the living space of your home without having to move, allowing you to continue living in your familiar surroundings. In addition, a well-executed extension can significantly increase the market value of your home, which can be beneficial if you decide to sell.

The function of an extension is also very flexible. You can use the new space as an extra living room, a home office, a playroom for children, or a hobby room. An extension can even serve as a conservatory, where you can enjoy light and views all year round. In addition, an extension can improve the layout of the existing spaces. For example, you could create an open kitchen or expand the dining room. Finally, building an extension offers the opportunity to invest directly in modern insulation, underfloor heating, and energy-efficient materials.

Differences between extensions and other additions

There are clear differences between an extension, a superstructure, and a conservatory.

An extension is a horizontal addition to the home. It is often easier to build and, in some cases, cheaper than a superstructure.

A superstructure, on the other hand, adds an extra floor without requiring additional floor space, but almost always requires a permit and is technically more complex.

A conservatory usually has a lot of glass, making the space feel light and open. It is often built as an extension of the living room, but in most cases a permit is also required for this.

Below is a brief overview of possible extensions:

When do you need a permit for an extension?

The regulations in the Netherlands regarding the construction of an extension are fairly clear, but contain many details that you need to take into account. It is essential to know in advance whether you need a permit. If you build without a permit when one is required, the municipality can impose fines and even require you to remove the extension.

In addition, there are often additional requirements for homes that are listed buildings or located in a protected town or village setting.

What rules apply?

The national rules for building an extension are laid down in the Building Decree. In addition, your municipality’s zoning plan determines what may be built on your plot. Municipalities sometimes have stricter requirements, for example to protect the streetscape or to limit nuisance to the surrounding area.

Permit-free extensions

In many municipalities, you can build without a permit if the extension is no larger than 30 square meters and no higher than five meters. In most cases, the extension may not be built within one meter of the property line, unless your municipality has established different rules. Furthermore, the extension must comply with the provisions of the zoning plan and may not be located in a protected city or village landscape.

Would you like to know exactly which rules apply to your extension and what you need to bear in mind? Take a look at the Omgevingsloket for detailed information and useful step-by-step plans.

When a permit is required

A permit is required if the extension is larger than 30 square meters or higher than five meters. This also applies if the extension conflicts with the zoning plan, if your home is a listed building, or if it is located in a protected cityscape. In addition, a permit may be required if the extension is placed too close to the property line.

The importance of the zoning plan

The zoning plan determines what may be built on your plot and under what conditions. It specifies, among other things, the maximum dimensions for extensions, the permitted number of floors, the function of the building, and the minimum distance from property boundaries.

It is wise to contact your municipality before starting your project to check what is included in the zoning plan for your address. This will prevent delays and unnecessary costs during the permit application process.

How do you apply for a permit?

Permits are applied for via the Omgevingsloket online digital platform. This is the central point of contact for all building and environmental permits in the Netherlands. Although the form is available online and appears easy to complete, submitting a complete and correct application requires careful preparation.

Incomplete or incorrect applications often lead to delays, because the municipality may request additional information or even reject the application. It is therefore wise to carefully gather all the necessary documents in advance and, if necessary, engage the services of a professional.

Step 1: Preparing the documents

Before submitting your application, you will need to gather a number of important documents.

First of all, you will need construction drawings showing the exact dimensions, materials, and colors of the extension.

You will also need a site plan that clearly shows where the extension will be located on the plot, including its position in relation to the main building and the property boundaries.

A technical description is also required. This describes how the construction will be carried out, what materials will be used, and how the insulation and installations will be arranged.

In some cases, a structural calculation is also required, in which a certified structural engineer guarantees the safety of the structure.

As an extra, you can provide photos or digital visualizations, especially if your home is located in a protected cityscape. This helps the municipality assess the impact of your extension on the surrounding area.

Step 2: Submitting the application

Once all documents have been collected and checked, submit your application via the Omgevingsloket (Environment Desk). Upload the required files and fill in the application form with the correct details about the project.

It is important that you fill in and check everything carefully, as incomplete applications can lead to delays. Also take into account the fees, the municipal costs for processing your application. These can vary from a few hundred to a few thousand euros, depending on the size of your project and the municipality.

Step 3: Assessment by the municipality

Once you have submitted your application, the municipality will start the assessment process. They will do this on the basis of the Building Decree, the zoning plan, and any additional municipal regulations, such as the aesthetic guidelines. The average processing time for a permit is between eight and twelve weeks.

Sometimes the municipality will request additional information or impose conditions that you must comply with before the permit is granted. It is advisable to respond quickly to this in order to avoid delays.

Step 4: Decision and granting of permit

When everything is in order, you will receive the environmental permit. From the moment this permit is granted, you may officially start building your extension.

It is very important that you do not start building before this, as this could lead to penalties such as fines, penalties, or even the obligation to demolish the extension.

How much does an extension cost?

The total cost consists of several components. You will need to take into account the costs for the design and the permit application, which can vary from approximately €2,000 to €5,000, depending on the complexity of the plans and the rates charged by the architect or structural engineer.

In addition, building materials and labor costs usually represent the largest expense. This includes foundations, walls, roof construction, insulation, windows, and doors. Installation costs for electricity, water, heating, and ventilation can also be considerable, especially if you opt for advanced systems such as heat pumps or solar panels.

You also need to factor in the finishing costs, including flooring, painting, wall finishing, and any modifications to the kitchen or bathroom.

Because construction projects often involve unforeseen expenses, it is wise to maintain a financial buffer of 15 to 20 percent of the total amount.

Average price per square meter

The cost per square meter for an extension depends greatly on the construction method and materials used, but also on the size of the extension. If you opt for basic materials and a standard finish, the average cost is between €1,200 and €1,800 per square meter. For a smaller extension, the cost per square meter may be slightly higher, because fixed costs (such as preparation and logistics) weigh relatively more heavily.

• If you opt for prefabricated elements (manufactured in advance) or modular construction, the costs per square meter may be lower than with traditional construction, especially for larger areas. Prefab construction ensures faster construction time and fewer labor hours on site, which reduces the price.
• On the other hand, custom solutions, luxury materials, and extra options such as underfloor heating, high-quality finishes, or special cladding increase the price per square meter. In that case, the costs are often between €2,000 and €2,500 per square meter or even more, depending on your requirements.

Please note that these prices include labor costs but exclude any additional costs such as foundation work, relocating pipes, or modifying existing installations.

Money-saving tips

There are various ways to save money.

• For example, you could choose to do smaller finishing jobs, such as painting, yourself.
• In addition, it is often cheaper to use standard materials rather than custom-made ones.
• Requesting multiple quotes helps you compare competitive prices.
• Considering modular construction or using prefabricated elements can also save time and money because they can be installed more quickly and efficiently.

The construction process step by step

Building an extension requires good planning and cooperation with various parties. Below you can read about the most important phases in the construction process.

1. Design and planning

In this first phase, you determine your wishes and possibilities. You then hire an architect or architectural draughtsman to create a suitable design. You ensure that the drawings meet the requirements of the municipality and that the design fits your budget. Finally, you check which permits you need and start the application process.

2. Applying for a permit

You submit the permit application to the municipality via the Omgevingsloket (Environment Desk). You then wait for approval, which usually takes eight to twelve weeks. Sometimes the municipality will ask you to make changes to the design. You respond to this as quickly as possible so as not to delay the process unnecessarily.

3. Start of construction

Once the permit has been granted, construction can begin. First, the groundwork and foundations are laid, which is crucial for the stability of the extension. Next, the walls and roof are erected, followed by the installation of electricity, water, heating, and ventilation. Finally, the interior and exterior finishes are completed so that the space is ready for use.

4. Completion and aftercare

Once construction is complete, you and the contractor will inspect the result. Any defects will be recorded and repaired. Keep all important documents, such as warranties and construction drawings, in a safe place. This is important for future maintenance and any sale of the property.

FAQ: Frequently asked questions about extensions

Is an extension really worth the investment? A well-planned extension not only increases your living space, but can also significantly increase the value of your home. Especially when you choose sustainable and modern materials, the extension often pays for itself when you sell. What’s more, it immediately improves your living comfort.

What is the difference between prefab and custom-made extensions? Prefab means that parts of the extension are manufactured in the factory and then installed on site. This speeds up the construction process and can save costs. Custom-made extensions are fully tailored to your wishes and specific situation, but are usually more expensive and take more time.

What sustainable choices will there be in 2025 when building an extension? In 2025, the focus will be on energy-efficient construction, with good insulation, the use of sustainable materials, and the integration of energy-saving installations such as heat pumps, solar panels, and ventilation systems with heat recovery.

Can Grand Renovation also implement these sustainable solutions for me? Yes, we are happy to guide you in making and implementing sustainable choices, from design to installation. In this way, we ensure that your extension is not only comfortable but also future-proof.

Are there subsidies available for building a sustainable extension? Yes, there are various subsidies and financial arrangements for energy-efficient home extensions, such as the Sustainable Energy Investment Subsidy (ISDE) and local municipal subsidies. We are happy to advise you on the possibilities and help you with the application.

Conclusion

An extension increases your enjoyment of your home and adds value to your property. The process of applying for permits, planning and executing the construction, and managing the costs requires attention and knowledge. With good preparation and the right partners, realizing your extension becomes a lot easier and more enjoyable.

Would you like to expand your home with an extension? Grand Renovation is here to take care of everything for you and guide you through the entire process: from applying for permits and designing to the final delivery. Contact us today for a no-obligation consultation. With our help, you will be enjoying extra space in your own home in no time!