How to Convert Your Attic Step by Step ?

Focus on Key Points to Verify for Step-by-Step Attic Conversion

Before engaging a specialized company, you must verify whether your attic is suitable for conversion. For this, several points need to be examined before starting the project.

Minimum Geometric Characteristics

First, if the ceiling height is insufficient, you won't be able to convert your attic. It should be at least 1.8 meters to be considered habitable. Additionally, a roof slope greater than 35° is required, with 45° being ideal. The nature of the framework also plays a role. If it is a traditional type and the available space is sufficient, the conversion won't present major difficulties.

However, in a trussed structure, the type of trusses used (wood or metal) determines the feasibility of the operation. In any case, your house's frame must not encroach on the floor. Moreover, since the latter will support the weight of the conversion, it must be load-bearing and stable enough. Consider the insulation materials, furnishings, and any partitions. Thus, reinforcement may be necessary depending on the nature of the existing floor.

Municipal Policies

You'll also need to inquire about your municipality's policies. Check if the local urban development plan (PLU) allows you to carry out such a project. Additionally, ensure from the outset that the future construction complies with the current urban planning regulations.

The third-party recourse right is, among other things, an essential point to consider. Your neighbors have two months from the date of posting the declaration or permit to contest the work (especially if the operation involves creating a window overlooking a neighboring house or apartment). Furthermore, if you live in a condominium, it's mandatory to inform the homeowners' association of such a project.

The Steps to Convert Your Attic 

When considering converting your attic, it's highly advisable to inquire with the town hall of your municipality. There, you'll find all the information regarding the formalities to follow and the assistance available to you for this operation.

In principle, if the area to be converted is between 5 and 20 square meters, a prior declaration of works (DP) is required. However, you'll need a building permit if the area exceeds 20 square meters (40 square meters when the municipality has a PLU). Moreover, the intervention of an architect is imperative for an area exceeding 170 square meters.

Works Required for Attic Conversion

There are several operations to carry out to convert your attic into comfortable and functional living space.

Access to the Attic

In most cases, unconverted attics have nothing more than a simple hatch for access. If you intend to convert them, you'll need to establish access that is both safe and easy. Additionally, it should allow for the easy transportation of furniture in and out. In this case, the choice of stairs depends primarily on the intended use of the space after conversion, particularly its level of traffic.

If it's a room you occasionally visit (for example, a playroom or a guest bedroom), a narrow staircase will suffice. However, for heavily frequented rooms, such as the living room, bedroom, or bathroom, you'll need a sufficiently wide model. In any case, if space is lacking on the lower floor for adding a real staircase, a ladder or a retractable staircase should be preferred.

Priority to Insulation

Insulation can be carried out either from the inside or from the outside.

Interior Insulation

Interior insulation is less expensive. However, it results in a loss of space due to the thickness of the thermal insulation. First, ensure that the roof covering is perfectly waterproof. Then, apply two crossed layers of insulation. To better protect the insulation from moisture, the roof should be covered with a waterproof membrane on the inside and a rain screen on the outside.

In terms of insulation, you can choose between glass wool, rock wool, expanded polystyrene (EPS), polyurethane foam, thin insulation, etc. These products all have good performance. The difference mainly lies in their ease of installation and cost.

Rock wool and glass wool are the most common and the most expensive. Moreover, they comply well with the new thermal and acoustic regulations. Available in rigid and semi-rigid panels, or flexible rolls with or without a vapor barrier, these mineral-based insulations adapt well to various dimensions between the rafters and joists.

For finishing, it's possible to cover the rigid face with paper or paint it. Polyurethane and expanded polystyrene foams in the form of rigid panels have very high thermal and acoustic performance. Lightweight and rigid, they cut easily with a standard tool, such as a jigsaw or handsaw. Moreover, they are non-compressible and comply with the latest insulation requirements. However, these products are expensive.

Exterior Insulation

This option allows for optimal insulation. It is ideal if you wish to preserve the available space in your attic. Unfortunately, external thermal insulation is only possible as part of a major project, which could include a complete roof renovation. Therefore, if you are planning to renovate your house's roof, consider insulating your convertible attic from the outside. However, note that this type of operation should be entrusted to a specialist in the field.

Regardless of the technique used, remember that attics can only be habitable when properly insulated. This operation aims to ensure a comfort level similar to that of other rooms in the house, both in winter and summer. At the same time, you reduce heat loss through the roof (about 30%), thereby achieving energy savings and reducing heating costs.