A flat roof is a flat, multi-layered structure that serves as an alternative to the classic roofs commonly found in Polish cities and rural areas. This type of roof is usually placed directly above the top floor of a building, creating a flat roof without an attic. The use of this solution also means that the rooms on the top floor have a consistent height without the loss of space that occurs with standard sloping roofs. However, it should be noted that a flat roof can also serve as a terrace or a garden. In the case of this type of construction, the load-bearing structure is a floor (usually horizontal), and any slopes are achieved by introducing a shaping layer.

Are flat roofs a novelty?

Contrary to what some may think, flat roofs are not a new solution. Investors successfully used them in the 1970s and 1980s. They were particularly popular among those who valued simplicity and low cost of roof construction. However, property owners began to notice the drawbacks of this solution, which eventually led to a decline in the popularity of flat roofs. Nowadays, they are experiencing a kind of renaissance as the technology of their construction has significantly improved due to better materials, resulting in higher quality, durability, and aesthetics.

Functions of flat roofs in single-family homes

A flat roof in a single-family property serves two functions simultaneously:

It acts as a ceiling over the top floor of the building,
It functions as the roof of the building.

However, in order for a flat roof to fulfill its intended tasks properly, it is crucial to use materials of appropriate quality. Practical skills of professionals who construct such roofs are also important. Therefore, it is best to entrust the construction of a flat roof (as well as other roof structures) to experienced specialists who have successfully completed many similar projects. A properly constructed flat roof will have sufficient strength to withstand various loads associated with strong winds, which are not uncommon in our geographic region, as well as snow accumulation or excessive heat during the summer season. Additionally, a well-executed construction will protect the house from heat loss and mechanical damage that may occur during long-term use.

Investors who choose comprehensive house construction with New-House can rely on professional support in administrative matters as well as all necessary construction works to create a single-family property. This means that we also take care of professional and art-compliant installation of a flat roof if you want such a structure to crown your house. We have a team of experienced specialists and modern technological facilities, which allows us to carry out even the most demanding roof projects. We have been operating in the single-family construction industry continuously since 1991. So if you are interested in building a house that will not consume your time, we are at your disposal.

Where can flat roofs be used?

Flat roofs are most commonly chosen by investors opting for modern-style single-family homes because this type of structure works perfectly with slight slopes of up to a maximum of 20 degrees.

In addition to minimalist single-family construction, flat roofs are also used in:

Multi-family housing,
Industrial construction,
Public utility buildings.

Types of flat roofs – classification based on construction

Non-ventilated flat roofs – solid roofs

This type of flat roof consists of tightly laid layers, which are additionally protected with thermal insulation material such as mineral wool boards, polystyrene boards, or polyurethane foam. Solid flat roofs can be either flat or sloped.

Ventilated flat roofs – channel roofs

In this case, the layer arrangement is similar to that used in solid flat roofs, with the difference that small channels are created in the substrate during construction, effectively preventing moisture from affecting the insulation material.

Ventilated flat roofs – double-layer roofs

In this type of flat roof, there is a space between two roof membranes, allowing external air to flow in and providing proper ventilation to the construction.

Classification of flat roofs – based on usage:

Utility flat roofs designed exclusively for human use – examples include terraces,
Utility flat roofs designed for the movement of passenger cars and trucks,
Non-utility flat roofs with limited access solely for checking the condition and performing maintenance of the roof covering,
Green flat roofs designed for intensive use with high vegetation requiring intensive care,
Green flat roofs designed for extensive use with low vegetation that requires minimal maintenance.

What materials are used for flat roof construction?

In practice, the construction of a flat roof consists of an efficient combination of several layers, where the lower layer, usually the load-bearing one, is made of reinforced concrete. However, it should be noted that it can also be made of concrete, wood, steel trapezoidal sheets, or wood-like materials. The most commonly used materials for insulation are mineral wool, mineral wool granulate, polyester and polyurethane foam boards, or expanded polystyrene. Additionally, a membrane can be used to protect against moisture, a layer of concrete covered with bitumen, or an air gap over which the proper roof covering is applied.

Fire resistance of flat roofs

Detailed requirements regarding the fire resistance of materials that can be used as building coverings can be found in the Regulation of the Minister of Infrastructure of April 12, 2002, on technical conditions to be met by buildings and their location (Journal of Laws No. 75, item 690, amendment Journal of Laws No. 109/2004, item 1156).

Investors should pay particular attention to the following part of the mentioned regulation: The covering of a building with an area larger than 1000 m² should be non-flammable, and its load-bearing part should be made of non-combustible materials. In the case when combustible thermal insulation is installed inside or on the load-bearing part, the fire resistance class of that part should not be lower than E15.

Insulation of a flat roof

In our geographic region, proper insulation of a flat roof is a crucial issue. The correct insulation is essential for both the thermal comfort of residents, especially those who spend a lot of time on the top floor of the house, and the ongoing operating costs of the property during the autumn and winter seasons. Rising prices of energy resources used for heating buildings make this aspect significantly more important, so it should not be overlooked.

Methods of flat roof insulation and the materials used for this purpose largely depend on the type of construction. For example, a concrete flat roof is best insulated with cellulose wool, while for a ventilated flat roof, rock wool granulate is recommended.

As for the method of insulating a flat roof, the most commonly used approach is machine-blown installation of the chosen insulation material. This method allows for a significant reduction in the entire process while not compromising the building's structure, ensuring safe use of the flat roof for years to come.

Advantages and disadvantages of flat roofs

Advantages of flat roofs:

Lower construction costs compared to sloping roofs,
High resistance of the roof to strong winds,
The possibility of lowering the roof construction and the entire building to the maximum,
No attic space,
The possibility of using the roof for additional purposes, e.g., as a green terrace,
The ability to increase the thermal insulation layer in the roof structure,
Increased roof covering area with a slight slope,
Effective prevention of moisture buildup,
Easy access to the roof, allowing for quick maintenance work and necessary repairs.

Disadvantages of flat roofs

Problems with snow buildup,
Diffusion, condensation, and water vapor removal issues,
Reduced protection of the thermal layer against adverse external factors.

Flat roofs, with the help of young designers who do not associate them with the uniform architecture of the 1970s, are regaining popularity. Their appeal is also influenced by various advantages and investors' preference for simplicity and minimalism. All of this contributes to the fact that clients of New-House are increasingly opting for flat roof constructions.