In principle, a distinction is made in roof construction between flat roof and pitched roof. The main criterion for this classification is the roof pitch. However, there is a transitional area: for example, a roof with a pitch of 7° or more is referred to as a pitched roof according to the DIN standard. In such a case, however, to speak of a pitched roof would certainly be inappropriate.
Flat roof structure
Flat roofs are a popular and practical design feature of modern architecture. They can be greened, walked on and extended relatively easily by adding roof extensions. In addition, the calculation of the statics, which is quite complex for a rafter roof, for example, is comparatively simple. To prevent sliding snow, you can install snow guards for metal roofs.
The usual roof structure of a flat roof is as follows:
1 – edge profile
2 – edge wedge
3 – Gravel fill (can also be implemented as a roof structure with a green roof)
4 – gapless waterproofing of the roof
5 – thermal insulation
6 – vapor barrier
7 – leveling layer
8 – reinforced concrete ceiling
9 – masonry
Roof construction for pitched roofs
The construction of a roof is based on many calculations concerning statics and material properties. These must be carried out individually for each roof. Nevertheless, there are only 2 basic forms of roof construction: rafter roof and purlin roof. In addition, there is the collar beam roof, which is an extended form of the rafter roof.
The rafter roof consists of a succession of stable beams (rafters), of which the opposite ones are connected to each other at the ridge. Thus, triangles are formed with the ceiling below. The eaves absorb the majority of the load forces, which is why stable connections must be constructed in the eaves area. You can read about the other functions of eaves here.
Valley beam roof
The collar beam roof is a further development of the rafter roof. Here, a transverse beam is inserted per pair of rafters, on which the rafters are additionally supported. In this way, a wider roof structure can be realized. Need to install snow guards on the roof for corrugated metal roofs.
The maximum width and pitch of the roof must be calculated individually for each building, depending on the floor area of the house, the materials used and the calculated load from wind, snow and the dead weight of the roof structure. A specialist is required for this. If you would like advice on roofing work or would like to make an appointment with an expert, you can search for specialist companies in your immediate vicinity here on saferoofexperts.com. The professional will also be happy to provide you with a no-obligation quote for roofing work.
The purlin roof is the most common roof construction for pitched roofs. Here, in addition to the purlins running across the rafters (ridge purlin, middle purlin and foot purlin), there are vertical stems that support the roof truss. Purlin roofs can be realized in comparatively large widths and shallow pitches, which is why they are so frequently used in house construction.
Depending on the shape and size of the house, several roofs – even of different shapes – can be combined. If two roof surfaces meet in a valley, a valley rafter provides the stable connection.
Different forms of roof construction
Roof shapes are very diverse. Thus, in addition to the flat roof, there are various pitched roof structures. The basic types are as follows:
- Gable roof
- Hipped roof
- Pitched roof
- Tent roof
- Mansard roof
In addition, there are modified forms such as the trapezoidal roof or the crippled hip roof. If different roof shapes are combined, care must be taken to ensure a seamless finish, especially in the area of the ridges that form the outer edges of roof surface joints. If there is no proper connection of insulation, insulation layer and roofing, thermal or cold bridges may occur.
Roof construction with and without rear ventilation
Another distinctive feature of the roof structure is the type of layering of load-bearing and insulating elements. A distinction can be made here between cold roofs (double-skin), warm roofs (single-skin) and inverted roofs (single-skin).
Cold roof (ventilated roof)
In the case of a cold roof, the roof structure consists of two shells enclosing a layer of air. This creates a chimney effect, known as rear ventilation. It ensures that moisture is transported away and cannot lead to moisture and mold damage. In addition, the installation of a sub-roof can also increase the rain resistance of the roof structure. You may also need to install standing seam snow guards on your roof.
Warm roof (non-ventilated roof)
Single-skin roofs do not have rear ventilation. As a substitute, a vapor barrier is installed from the inside, which ensures that moist room air condenses in front of the insulation layer and does not enter the roof structure in the first place.
There are many things to consider, especially when insulating roofs. If work is not done carefully, penetrating moisture can quickly cause serious damage to the insulation layer or the roof structure. For this reason, all types of roofing work – regardless of the roof structure – are always the responsibility of a certified roofer. In addition to roofing and cleaning, this professional will also perform work such as green roofing, replacement or renovation of your roof ridge, or installation of photovoltaic systems.
Inverted roof (non-ventilated roof)
The inverted roof is a variation of the warm roof in flat roof constructions. In such a construction, which is also single-skin, the insulation layer is placed above the roof waterproofing. It is therefore the last layer to the outside, which reduces the thermal stress on the roof cladding, which usually forms the outer finish of a roof, and thus increases the service life of the roof. In addition, better access is possible in case of repair work. Inverted roofs can be realized since the development of weather-resistant insulation materials. Keep your roof clean with the Karcher K7 pressure washer.
If you would like to find out more about how roof repairs Auckland works and how it is constructed, saferoofexperts.com has everything you need to know about the subject.
The first decision to be made when building a new roof is: flat or pitched roof? The latter can be roughly divided into rafter and purlin roofs. And here, too, there are differences in the external shape of the roof. So anyone planning a new roof should consult a roofer for advice on all the options and their specific properties!