Building a home extension? Top 5 FAQs you must know

Building a home extension? Top 5 FAQs you must know


Expanding your living space with a home extension can increase your property's value and improve your quality of life. In this guide, Diagonal Renovations has answered some of the most common questions they get from their clients, to help you navigate home extensions in the Netherlands.

Planning to build a home extension? Contact Diagonal Renovations to get a quote!

1. Why should I build a home extension?

To answer that, here is an example: a family with two girls with a two-story 100m2 terraced house wanted to build a 50m2 top floor, like their neighbours. After the architect finalised the drawings and submitted the permit request, Diagonal Renovations prepared the quote and started working. Building the structure took four weeks, and finishing the interior took about eight more weeks.

As a result, the family now owns an extra 50m2 living area that adds 250.000 euros to the value of their house. Adding value and space to a house can be especially advantageous if you plan to sell your home.

Home extension

2. Do I need a permit for a home extension?

The obligation for planning permission varies by location and the extension’s size, but in most cases, when building another floor on a flat roof, you must get a permit, as it entails calculations and reinforcement work. The municipality usually takes six to eight weeks to review and approve the permit request.

3. How can I ensure my home extension is energy-efficient?

Energy-efficient construction is essential for environmental reasons and reducing long-term operating costs. Wall insulation, solar panels, windows, heating systems - and many other things - determine your home energy consumption.

In the long run, basing the planning work on an energy-efficiency improvement plan can save you money when financing the project or selling the house. Ensure your project's contractors follow the energy advisor's report, too.

4. How does building a home extension work?

New construction has two main phases:


The construction work is delivered in "casco" condition. This means that the builder takes care of the structural work, making sure the property is wind- and watertight: at this stage, the construction is essentially a skeleton with windows and glass, doors, and roof tiles.

The interior

The work on the interior starts where the construction ends. The client and the architect must make a long, detailed task list to take the property from a skeleton to a liveable space.

5. How much does a home extension cost?

The cost of a home extension can vary widely depending on factors such as size, complexity, location, and materials. To avoid unexpected expenses during the project, ensure the final quote corresponds to the planning and materials stated in the project's final drawings.

Home and roof extension prices in casco condition vary between 1.500 to 2.000 euros per square metre. Then, for the interior, depending on the quality of the accessories, materials, and finishing level, prices range from 700 to 1.400 euros per square metre.

Experienced professionals, such as the professionals at Diagonal Renovations, should provide expert guidance and insights from previous projects that will ensure a successful outcome.

The financial advantages

To understand the financial advantages of building a home extension, let’s go back to the example from before:

  • 100m2 terraced house: €500.000 = €5,000/m2.
  • 50m2 roof structure + finishing: €135.000 = €2.700/m2.
  • Total investment on 150m2 house: €635.000 = €4.233/m2.
  • Similar 150m2 house’s price: €750.000 = €5.000/m2
  • Added value for the 150m2 house: €115.000 = €2.300/m2. 

The 50m2 roof construction cost €135.000 [= €2.700/m2]. The family, who bought the house for €5,000/m2, expanded the house by slightly more than half the market price for a square metre in the area. Now, that's a real bargain!

About Diagonal Renovations

The projects at Diagonal Renovations are led by Ben Engelsman, a real estate professional who oversees the construction teams and tradesmen who carry out the work on site.

With years of experience, Ben and his expert advisors lead the operation to deliver projects successfully, on time and at the highest quality.

Why work with Diagonal Renovations? diagonal-renovations-image.jpg

Here is why working with Diagonal Renovations is a great idea:

  • All of their projects are covered by commercial liability and construction all-risk insurance.
  • Project phases are supervised and approved by an experienced construction consultant who ultimately confirms the work is of top quality.
  • With their professionals covering all construction sectors and their extensive network of experts, they can handle any renovation project.

Contact Diagonal Renovations

Planning to build a home or roof extension? Contact Diagonal Renovations to get a quote!



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