Why choose Avenir Renovations?
Why consider a storey addition with a flat roof?
This type of storey addition is at the crossroads of design and functionality. It is appealing for both its aesthetics and its practicality and energy performance.
Gain space without losing ground
An additional floor means extra living space, without touching the garden or encroaching on the plot.
Obtain an accessible or technical flat roof
You can create a terrace, a hanging garden, or a green roof, or simply opt for a well-insulated technical flat roof.
Modernize the style of your home
The flat roof gives a contemporary silhouette to your home. When well integrated, it enhances its architecture and fits into an urban approach.
Adapt to municipal constraints
Some Belgian municipalities impose height or roof slope restrictions. The flat roof can be an intelligent and regulatory response.
What options does Avenir Rénovations offer?
Each project is studied to meet the client's expectations, the structural constraints of the building, and local regulatory requirements.
Technical and architectural advantages
High-performance technical solutions and architecture designed to combine aesthetics, durability and functionality.
Flat roof, clean facades, modern joinery: the house takes on a design look, in line with contemporary Belgian constructions.
A rooftop terrace is a unique asset for daily comfort as well as resale. You benefit from a bright and open space.
We use high-performance multilayer membranes suitable for flat roofs, whether accessible or not.
Warm roofs, high-density rigid insulation, airtightness and waterproofing: energy performance is guaranteed.
What budget for a storey addition with a rooftop terrace?
The price depends on the type of structure, the accessibility of the site, the level of fit-out of the roof, and the materials chosen.
| Type of project | Average price per m² including tax |
| Storey addition with non-accessible flat roof | 1,800 to 2,300 € |
| Storey addition with fitted rooftop terrace | 2,000 to 2,500 € |
A personalized quote is provided after a technical study on site.
Why call on Avenir Rénovations?
- Custom design, tailored to each municipality
- Partner architects specialized in contemporary renovation
- Network of qualified craftsmen for flat roofs
- Ten-year guarantee on structure, waterproofing, and roofing
- Single point of contact for the entire project
- Administrative procedures managed from A to Z
FAQ: Storey Addition with Rooftop Terrace
Is a permit required to create a rooftop terrace in Belgium?
Yes, absolutely. Any storey addition with a flat roof alters the volume of the building, which requires obtaining a building permit. This permit is essential, whether the roof is accessible or not. If you are considering a terrace, the regulations are even stricter: mandatory guardrails, secure accessibility, enhanced waterproofing, rainwater management... Each Belgian municipality may impose its own requirements (maximum height, facade appearance, view of neighbors). At Avenir Rénovations, we handle the urban analysis, permit application with the architect, and communication with the municipal administration. You save time and avoid design errors. Proper regulatory anticipation protects you in the long term and ensures the validity of your project.
Is it possible to create a real terrace on a storey addition?
Yes, if the structure is designed for that purpose. A terrace on a roof requires a specific technical design: the slab must support operational loads (furniture, people, plants), the slope must allow for water drainage, and insulation must be reinforced. We install a multilayer waterproof membrane, protected by slabs, wooden decking, or a mineral coating. Usability can be enhanced with lighting, an outdoor socket, a tap, or even privacy screens. This type of terrace is a real plus for daily comfort. It also significantly enhances the house by offering a private outdoor space, which is rare in urban areas. It is a bold and profitable choice that we master from design to execution.
What are the insulation and waterproofing constraints of a flat roof?
They are strict, and rightly so. A flat roof is more exposed to moisture, frost, and heat than a sloped roof. In Belgium, regulations impose minimum thermal insulation values (U-value) as well as precise waterproofing standards. Always require warm roofs, with external insulation (PIR or rigid mineral wool), vapor barrier, and hot-welded synthetic membrane. For accessible roofs, mechanical protection must be added. To mitigate the risks of infiltration and overflow, it is essential to perform waterproofing checks around the entire perimeter of the roof. The presence of this system not only prevents rainwater from flowing down the facade of the building but also prevents infiltration into the walls. You can rely on our renovation professionals to achieve perfect waterproofing around frames, drains, guardrails, and wall junctions. Finally, ventilation and roof slope are designed to avoid water stagnation. This way, you benefit from thermal comfort all year round, without condensation or leaks, and a durable and guaranteed roof.
Trust your project to flat roof experts
Are you considering expanding your home and enjoying a unique outdoor space? Avenir Rénovations supports you in the creation of a storey addition with a rooftop terrace, compliant, durable, and elegant. Request your free study today.
