Renovating a basement: our complete guide


Would you like to expand the living space of your home by adding new living areas? Renovating a basement or cellar can be an interesting solution to achieve this goal. Indeed, you can create a home theater, a playroom for your children, or even an additional bedroom. Moreover, in real estate investment, this contributes to the appreciation of your property for future sale. However, for your renovation project to be successful, you need to consider several factors. You must especially consider issues of humidity, ventilation, brightness, and insulation. Therefore, the renovation and construction work associated with your basement development project require a more or less significant budget. Additionally, according to the current law, you will need to go through certain administrative procedures to undertake such an operation.

What permission is needed for basement development?

Before renovating your basement, it is necessary to ensure that it complies with current legislation. Initially, you must verify that your house is not located in a flood zone where such operations are not allowed. Depending on the nature of your cellar, you will need to complete some administrative procedures to obtain permission to carry out its renovation, namely :

  • a prior declaration of work: if the area ranges between 5 and 20 m2, or less than 40 m² if the municipality is subject to a PLU (Local Urban Plan) or a POS (Land Use Plan);
  • a building permit: beyond 20 m², or 40 m2 (with PLU or POS) or if your development involves a modification of the building's structure;
  • authorization from an architect: if the newly created room results in an increase of more than 150 m² of the total surface area of the dwelling;
  • approval from the condominium association: if your home is located in the heart of a building;
  • a declaration to the tax authorities: if your basement has a height of less than 1.80 m.

However, if the extent of your basement is less than 5 m2, you can carry out your project without any authorization.

What type of room to create in your basement or cellar?

The type of room that can be created in your basement generally depends on its ceiling height. To give you an idea, here are some tips to consider :

  • less than 2 m in height: a space dedicated to storage or stockpiling, which can be used as a wine cellar ;
  • less than 2.10 m in height: a space dedicated to temporary activities (home theater, playroom, workshop, or guest room) ;
  • from 2.40 m in height: a living room, an office, a gym, a studio, or a bedroom.

Additionally, you can also create a laundry room, a kitchen, toilets, or a bathroom. However, this requires extending the water network, which can be complicated and costly, especially if the pipes are too far from the basement.

How to Renovate Your Basement?

Generally, converting the basement of a house or apartment into a livable space is quite challenging. Its renovation requires various works and efforts.

Get assistance from an architect

First and foremost, you need to have the right support to avoid mistakes in your project. Moreover, carrying out this type of renovation requires specific skills. Therefore, it is highly recommended to seek the help of an architect. They will assist you throughout your project, offering comprehensive support from feasibility study to project completion. Their tasks mainly involve creating plans, handling administrative procedures, selecting materials, and overseeing construction.

Check the ceiling height

Ceiling height plays a crucial role in basement renovation. When it is less than or equal to 2.10 meters, your project will be limited to a partially usable room. However, there is a trick to create a comfortable living space.

You can excavate the floor to gain a few extra centimeters. After that, you will need to lay a reinforced concrete slab. However, such works are challenging and costly. A professional engineering firm should first check the depth and condition of the existing foundations. Depending on their findings, it may be necessary to reinforce these foundations with micropiles.

Address basement moisture issues

Basements can sometimes be prone to moisture. Therefore, it is essential to plan for some drainage works.

For condominiums

In the case of a condominium, you will need to implement a waterproofing system (or tanking) from the inside of your basement. This method involves applying a special, thick mortar layer (about 30 mm thick) on the walls. Then, a waterproof screed should be poured onto the floor slab, and waterproof sheets or panels should be installed on the floors and walls.

For houses

In a house, the most affordable practice is to drain the surrounding soil. This helps to divert water runoff away from the basement. If possible, excavate the exterior walls to apply a more waterproof coating. You can also inject an anti-moisture resin into the walls.

Setting up a ventilation system

The installation of a ventilation system as part of basement renovation is of crucial importance. This ensures a healthy and comfortable environment. Additionally, basement renovation requires careful consideration of air circulation, especially in spaces such as a game room or a bathroom. Creating a livable basement, integrated into the basement renovation project, requires close collaboration with qualified professionals. For example, you can enlist bathroom installers and carpenters to set up a discreet and efficient ventilation system.

The choice of ventilation system must adapt to the specificities of the basement, taking into account factors such as ceiling height and space configuration. Basement floor renovation works, sometimes involving floor tilers, must be coordinated with the installation of the ventilation system to ensure seamless integration. Whether the basement renovation project aims to create a new living space or to refurbish an existing basement, ventilation is a key element to prevent moisture, unwanted odors, and ensure optimal air quality.

Companies specializing in terraces and conservatories can also provide expertise in integrating ventilation solutions suitable for basement layout. This process is an integral part of the renovation project, where coordination between different trades, such as kitchen designers and painting and wall covering companies, is essential for project success.

Installing a well-thought-out ventilation system is, therefore, an essential step in any basement renovation project. It not only contributes to the occupants' comfort but also preserves the integrity of the space created, whether it's a game room, a bathroom, or any other renovated basement.

Moreover, the ventilation system not only refreshes the ambient air but also evacuates water infiltration and pollutants from your basement. Ideally, installing a single or double-flow Mechanical Controlled Ventilation (MCV) system is recommended. If space is limited, an insufflation ventilation system will suffice.


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Planning for insulation and accessibility of your basement

Insulation and accessibility are essential steps in basement renovation. It requires careful planning for a successful project.

  • Properly insulating the floors

To insulate your basement floor, it is advisable to lay down a vapor barrier directly and extend it a few inches up the wall. Additionally, you can install insulating panels on which your future floor covering will be placed. To optimize floor insulation, consider using hardwood, laminate, thick carpet, or linoleum.

Be cautious with wood as it doesn't tolerate moisture well. Your basement remains naturally damp regardless of the renovation work you undertake.

  • Properly insulating the walls

If the walls are even, you can directly attach thermal panels consisting of plasterboard and insulation. It's also possible to insert insulation between the wall and a metal frame onto which plasterboards will be fixed. Apply a layer of insulating paint on the boards to enhance insulation. Additionally, depending on your preference, you can install wall tiles or plaster.

  • Properly insulating the ceiling

Ceiling insulation requires a different method from the others. If the height allows it, consider installing insulation to protect against damage from fixed pipes. You can also place extruded polystyrene boards that improve heat retention.

For greater efficiency, apply anti-humidity paint. This can protect your ceiling from mushroom growth, for example.

Furthermore, if not already in place, you'll need to plan a means to access your new room, such as a staircase.

Planning for basement lighting

Generally, the lack of natural light makes basement renovation challenging. To address this issue, several solutions are possible, including :

  • installing a glazed surface or glass bricks on the ground floor to bring in light from the upper space (living room, entrance hall...) ;
  • creating an opening in the ground floor to establish an empty space allowing direct view of the basement (not ideal for a bedroom, a game room, or a cinema room) ;
  • installing a skylight: a device that transmits natural light captured from the facade to the basement ;
  • setting up artificial light sources: you can install ceiling spotlights, wall sconces, or lamps.

For semi-basement floors, replace existing openings with glass windows. It's also possible to create additional openings (grilles). For houses, consider installing window wells or louvered vents to facilitate window installation in your basement.

Considering various installations for your basement

To make your basement more livable and comfortable, it's necessary to connect it to the electricity grid. Create one from the main panel of the house. Also, consider routing wires inside the wall partitions of your basement for discretion.

Regarding the heating system, you can opt for :

  • installing electric radiators: easy to set up and aesthetically more suitable for an optimized heating system ;
  • extending the existing network to the basement.

Furthermore, if you plan to convert your basement into a kitchen, toilet, or bathroom, water networks must be well established. Installing a sump pump is one of the best solutions if the drainage pipes are too far from the room. However, this requires a significant budget and complex work.

What are the prices for basement renovation ?

The budget for a basement renovation project depends on its size, the complexity of the work, and the materials chosen. This cost typically ranges from €1,200 to €2,200 per square meter.

The final price of basement renovation works depends on :

  • The condition of the room,
  • Its surface area,
  • The complexity of the operations to be carried out,
  • The quality of the materials used,
  • The fees of a study office and those of the architect.

Don't hesitate to request multiple quotes to find the offer with the best value for money.

What are the technical aspects of basement renovation?

When it comes to the technical aspects of basement renovation, it's imperative to consider every detail to ensure the success of the project. Basement renovation requires meticulous planning, especially regarding ceiling height, a crucial element in defining available space. Whether creating a bathroom, a game room, or a multipurpose space, basement renovation often involves significant work, impacting the floor, walls, and space in general.

Wall coverings play a vital role in basement renovation, both aesthetically and functionally. Basement floor renovation works require special expertise, involving qualified floor tilers. By exploring ideas on platforms like Pinterest, for example, you can discover photographic inspirations for basement design, offering creative perspectives for each basement renovation project.

Ceiling height can also influence design choices, especially when considering converting the basement into a bathroom, a game room, or any other functional space. Basement renovation works require precise coordination between different artisans. These include bathroom installers, carpenters, and kitchen designers, to ensure seamless integration of each element.

Thus, the basement renovation project aims to transform a cellar into a versatile living space. So if you want to create a new basement layout, collaborating with companies specializing in terraces, conservatories, painting, and wall coverings is essential. Their expertise ensures exceptional results. Choosing qualified artisans in the field of basement renovation, such as our architects, is therefore the key to successfully completing a project that optimizes every square centimeter of this often underestimated space.

How to manage a basement renovation project?

A step-by-step guide is essential for effectively managing a basement renovation project, especially considering the specifics related to basement remodeling. The first step is to clearly define the project's objectives. Whether it's creating a bathroom, a game room, or simply optimizing space, a precise vision guides the entire basement renovation process.

The second step involves a thorough assessment of technical constraints, such as ceiling height and space configuration. This often requires the collaboration of qualified professionals such as floor tilers, carpenters, and bathroom installers to ensure a precise understanding of basement floor renovation works.

Careful planning is the third crucial step in managing a basement renovation project. This includes coordinating work, selecting competent contractors, and establishing a realistic budget. Terraces, conservatories, and wall coverings can all be integrated into this planning, requiring precise coordination between different specialized companies.

The fourth step is the execution of the works, where renovation professionals, from basement floor tiling to bathroom installations, come into action. Smooth communication between floor tilers, kitchen designers, and painting companies remains essential for ensuring a harmonious progress.

Finally, the fifth step involves thoroughly inspecting the completed work. This is where the basement layout comes to life, whether it's a game room, a bathroom, or any other livable space. Special attention is paid to the quality of finishes, thus ensuring the satisfaction of the occupants of the renovated basement.

In summary, effectively managing a basement renovation project requires a methodical approach, from defining objectives to final inspection. Each step, coordinated with qualified professionals, contributes to the success of a renovation project that fully optimizes the basement space.

How to choose a qualified architect for basement renovation?

Basement renovation works require the expertise and skills of our architects. Indeed, only professional architects can offer you a satisfying result at all levels.

When selecting qualified contractors for a basement renovation project, caution and diligence are essential, especially in the context of basement remodeling. The first step is to conduct thorough research using resources such as personal recommendations, online reviews, and specialized platforms. This allows you to identify professionals experienced in renovating your basement, highlighting previous achievements and specific skills.

Ceiling height and basement complexity require contractors with specific expertise. Experienced floor tilers, seasoned carpenters, and qualified bathroom installers are essential to ensure an optimal result. Choosing competent contractors in these specific areas contributes to the success of the basement renovation project.

The basement renovation site also requires the coordination of different skills, including kitchen designers, companies specialized in terraces and conservatories, as well as experts in painting and wall coverings. Make sure to choose professionals whose experience covers all the work required for basement remodeling, ensuring consistency in project implementation.

An important aspect when selecting qualified contractors is verifying licenses and insurance. This not only ensures the legitimacy of the company but also provides protection in case of incidents during the renovation works. An entrepreneur with these qualifications demonstrates commitment to quality and safety, crucial elements for a successful basement renovation project.

In conclusion, selecting qualified contractors for basement renovation requires a methodical and attentive approach. Thorough research, verification of specific skills, and assurance of licenses are essential steps to ensure the success of the basement remodeling project.

Mathieu Amara

Mathieu Amara

Graduated in political science, I have always been passionate about renovation and construction work.

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