An extension at the back of your home can be an excellent way to create extra living space and increase your property value. In this article, we discuss the costs and considerations for realizing an extension, including material choices, foundation options, and licensing requirements. We provide practical tips for informing your neighbors and complying with legislation, as well as advice on design, dimensions, and the use of prefabricated elements. Discover how to plan and implement the perfect extension to enhance your home's comfort and value.

Regulations

Permit-free construction

In most cases in the Netherlands, you can build an extension at the back of your house without a permit. This means you don't need formal approval from the municipality, making the procedure considerably faster.

However, it is crucial that the extension meets certain conditions:

• The extension must not be deeper than 4 meters.
• The extension must not be higher than 30 cm above  floor.
• The extension must remain within a fixed distance of the property boundary.
• The total area of all outbuildings together does not exceed 50% of the plot area, with a maximum of 150 square meters.

Always check your municipality's rules, as local guidelines may differ from national rules. This extra check can prevent you from having problems later and helps ensure that your project runs smoothly.

When is a Permit Still Necessary?

In some cases, you do need a permit for an extension. Large extensions that cover the entire back of your house or occupy a significant part of your plot are often outside the license-free rule. In such cases, it is important to consult with the municipality in time.

For larger projects, you often have to apply for an environmental permit. This means that you must submit detailed drawings and a description of the project. The municipality will then assess whether your plans comply with the construction and environmental rules.

Always contact your municipality to find out the specific requirements for your extension. This ensures that you are not faced with any surprises and that your project runs according to the rules. More information about license applications can be found on the website of Bouwadvies Shop.

Neighbours law

The neighbor law is an important aspect to keep in mind when expanding the rear of your home. It determines what is allowed and what is not, so you and your neighbors can live in harmony. According to the neighbor law, when expanding, your neighbors have the right to keep their view. This means that neighbors are not allowed to build above a certain height. If your view is obstructed, the rules are broken.

Another important part of neighbor law is the so-called ladder right. This means that you can enter your neighbor's yard to renovate or maintain your home, provided you inform them on time and there are no other options for the work. You can read more about this in the Civil Code, book 5, articles 37 to 59.

Practical tips:

• Inform your neighbours about your renovation plans in good time.
• Make sure your plans meet the height requirements so as not to obstruct your neighbor's view.
• Only use the ladder right when absolutely necessary and give your neighbours enough time to prepare for this.

Respecting neighbor law prevents conflicts and ensures a pleasant living environment for both you and your neighbours.

Design and Dimensions

When planning an extension at the back of your home, several factors are very important. Consider the size and width of the extension, the installation of windows and doors, and the necessary construction calculations.

Size and Width

The size of your extension determines how much extra space you gain. A smaller extension of 10 m² will be less expensive than a larger one of 40 m². However, surface area is also crucial for increasing property value. For example, an extension that is 3 meters wide and 4 meters deep provides sufficient space for an additional dining room.

It's important to consider not only the extra square footage but also the optimal layout of the new space. Ensure the new extension integrates seamlessly with the rest of your home for the best results.

Windows, Doors and Skylights

Windows and doors are essential for daylight and ventilation. Consider patio doors for easy access to your garden. A large window can offer a pleasant view and bring more light into the room.

Skylights are also a great option, especially for adding light to the center of the room. However, installing a skylight may require additional roof elevation. Proper planning ensures that these elements not only enhance the aesthetics but also improve the functionality of your new space.

Construction calculation

An extension must be sturdy and safe, making a good construction calculation essential. This calculation considers the foundation and materials used, such as brick or wood. Often, it's necessary to apply for a permit where the construction calculations are reviewed by the municipality. Even when a permit is not required, a construction calculation is useful in case of complaints leading to a construction stop.

Using reliable constructors and construction advice ensures the integrity of your extension. Ensure all structural elements are coordinated and load-bearing parts are strong enough for the planned extension.

Foundation for the Expansion

There are different types of foundations that you can consider for an extension. The right type of foundation depends on factors such as the soil condition, the weight of the extension and local building regulations.

Strip foundation

• Description: Concrete strips under load-bearing walls, often 50 cm wide and 30 cm deep.
• Use: Suitable for light to medium duty structures on stable ground.
• Benefits: Simple and cost efficient.

Plate foundation

• Description: A thick concrete plate that distributes the weight evenly.
• Use: Ideal for heavy construction or when a stable surface is needed over a larger area.
• Benefits: Provides excellent stability and support, more expensive than strip foundations.

Pile piles

• Description: Long poles that are driven deep into the ground until a solid layer of earth is reached.
• Use: Suitable for areas with weak or unstable soils, such as clay or peat, and at high water levels.
• Benefits: Very stable base, prevents subsidence in problematic ground conditions.

Screw piles

• Description: Steel poles that are screwed into the ground.
• Use: Suitable for lighter structures and places where pile-driving vibrations are not desirable.
• Benefits: Fast installation, less disruption to the environment.

Choosing the right foundation is crucial for the stability and durability of your extension. Always consult a structural engineer or contractor to determine which foundation is best for your specific project and ground conditions.

Materials and Construction

When expanding your home at the back, it is important to choose the right materials and construction methods. This includes the choice of building materials such as cellular concrete or wood, insulation, roofing and the use of prefab elements.

Material selection

When building an extension, various technologies are available for the construction of the walls, such as cellular concrete and timber frame construction.

Aerated concrete

• Description: Lightweight, fire-resistant material that provides excellent insulation.
• Use: Suitable for both load-bearing and non-load-bearing walls.
• Benefits: Good thermal and acoustic insulation, easy to process, durable and fire resistant.

Timber frame construction

• Description: Construction technology in which a frame made of wood forms the basis, filled with insulating material and lined with plates.
• Use: Suitable for fast, lightweight structures.
• Benefits: Flexible design, good insulation values, quick to build, environmentally friendly.

Both technologies offer unique benefits and can be adapted to the specific requirements of your extension project.

Insulation

Good insulation is crucial for the comfort and energy efficiency of your extension. Roof insulation, wall insulation and floor insulation are all important to minimize heat loss. Insulating materials used are often HR++ glass, glass wool, rockwool, PIR and EPS (expanded polystyrene). Insulation not only helps to reduce energy costs, but also contributes to a comfortable living environment by better managing the temperature controller and providing sound insulation.

Roofing

The choice of roofing depends on the type of roof. Flat roofs often imply EPDM, bitum or PVC for their waterproof properties and durability. For sloped roofs, roof tiles, slates and metal roofing popular options. A well-chosen roof covering not only protects against weather influences, but also contributes to the overall appearance of the extension.

Using Prefab Elements

Prefab elements are parts that are made in a factory and assembled on site. This can include walls, roofs and even entire rooms, for example. The materials commonly used for precast elements are concrete, wood, and steel. The use of prefab ensures a faster construction time and less inconvenience on site. Prefab is often cost-efficient and the quality is consistent due to the controlled production method.

Finishing

When finishing the extension, there are two important aspects: interior finish and facade cladding. These determine the final appearance and functionality of the space.

Interior finish

Interior finishing involves completing the inside of your extension. Drywall is commonly used for cladding walls and ceilings, offering easy installation and a sleek finish.

Further plastering of walls and ceilings provides a smooth, even surface that can be painted or wallpapered. The type of finish you choose impacts the atmosphere and functionality of the space. Opt for a modern, minimalist look with clean lines, or a classic style with decorative frames and ornaments, depending on your design preferences. Proper finishing enhances both aesthetics and usability.

Facade cladding

The exterior of the extension is shaped by the facade cladding. The material you choose is important for the durability and maintenance of your home. Popular choices include brick, wood, and aluminum.

• ‍Brick gives a traditional and robust look and is also easy to maintain.
• ‍Wooden siding provides a natural and warm appearance, but requires more maintenance than brick.
• ‍Aluminum can provide a modern and sleek look, and is weatherproof and easy to maintain.

Costs and Financing

When planning an extension at the back of your home, you should pay close attention to the costs and ways to arrange financing. Here are some important aspects to keep in mind to avoid unexpected costs and make use of subsidies.

Budgets and Prices

Making a detailed budget is essential to keep a realistic budget. The costs of an extension vary greatly. The average price is between €30,000 and €80,000, depending on the depth and width, prefab or custom work, and the materials used such as bricks or aluminium.

An extension at the back of your home costs an average of €2,500 per square meter. A smaller extension 1 meter deep costs an average of €15,000 to €18,000, while a larger extension of 20m² can cost around €50,000.

It is wise to request multiple quotes for an accurate picture of the possible costs. These costs include labour costs, material costs and any licensing costs. Don't forget to include VAT, which may vary by region and type of work.

Avoiding Unforeseen Costs

Unforeseen costs can severely disrupt your budget. Thorough preparation helps prevent this. Pay extra attention to the foundation and the condition of your home, as unexpected extra work often arises here. Always have an architectural inspector assess your home before starting.

Consider savings options: prefab structures can be more cost-effective than custom builds, and opting for less luxurious materials can also save money. Proper planning and budgeting are crucial to ensure a smooth and affordable extension project.

Frequently Asked Questions

What is the average cost per square meter for an extension at the back of a house?

The average cost of an extension at the back of a home is around €2,500 per square meter. This rate may vary based on the materials used and the complexity of the project. For example, an extension of 20 m² costs an average of €50,000.

What types of materials are recommended for an extension and what are their costs?

Bricks, aluminum and double glazing are often used for an extension. Bricks are durable but can be more expensive than prefabricated materials. The materials you choose have a major impact on the overall cost, so consider all options carefully.

What factors should be taken into account when determining the foundation for an extension?

When determining the foundation for your extension, you should pay attention to the surface, the total load that the structure will bear, and the local building regulations. A stable and well-planned foundation is crucial to prevent cracks and subsidence. Always consult a professional to ensure that your foundation meets all safety standards.

What are the most important considerations when planning an extension to an existing home?

When planning an extension, you should consider permits, the impact on your garden, light, and the accessibility of the extra space. Make sure that the new space fits well with the existing structure of your home. Consult with specialists to ensure that all aspects of the renovation are carried out properly.

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