Why should you choose a pitched instead of a flat roof?

Wutte Weingut covered with Tondach clay roof tile © Alexander Schleissing
Are looking for a suitable roof construction for you newly constructed house? The following information helps you to make the right choice and provides a compact overview.

Wienerberger pitched roof solutions –“Everything from one source”

Roof solutions by Wienerberger include roof tiles, fittings and also technical components like underlays, storm fixation systems, snow retention systems, insulation, etc.

Besides the two main brands Koramic in Western Europe and Tondach in Eastern Europe, we provide Sandtoft and Keymer roof tiles in the UK, ZZWancor clay roof tiles in Switzerland and high-end plain tiles from Aléonard in France. Keymer and Aléonard both stand for long history and tradition, Keymer are genuine handmade British clay roof tiles.

Under the quality brand of Koramic, Wienerberger provides individually tailored solutions for all common requirements, that is
  • insulation systems installed on top of the rafters
  • diffusion-open underlays
  • a great variety of durable Tondach roof tile models
  • ridge / hip solutions
  • ceramic and non-ceramic accessories
  • as well as a wide range of different services
The roof solutions are combined as individual “packages”, which allow roof constructions according to European building regulations in the refurbishment and new construction segment through to the implementation of a passive house standard.

Pitched roof vs. flat roof

The roof as the upper termination of a building is executed in different ways depending on the angle of the roof pitch. When does one speak of a pitched roof?
  • Pitched roof: inclination angle of 15° to 70°
  • Low-pitched roof: 8° to 15°
  • Flat roof: < 8°
According to a study by TU Wien a house with a pitched roof is 12.5% more compact than a house with a flat-roof providing same living space. This makes the building more effective thermally, as it reduces the surface of the walls in contact with the outside world. Pitched roofs are especially common in areas with wet and changing weather conditions, whereas flat roofs are more popular in dry, hot areas.
Wienerberger has designed special regional products for low-pitched roof solutions. For a roof pitch between 10°and 15°, Wienerberger offers technically advanced roof tiles, fittings and accessories. These system solutions provide absolute resistance against severe weather conditions.
Pitched roofs have a firmly secured place in modern architecture. Their versatility makes them ideally suited for the implementation of innovative design solutions, resulting in the desired futuristic-looking rooftops that reflect the modern world.

Pitched roof has advantages over flat roof

A study by TU Wien (Vienna University of Technology)
A study in Austria has shown that the costs for the roof as a building component (roof covering and substructure) are cheaper for pitched roofs than for flat roofs in terms of both the initial investment (production) and over the life cycle (50 years).

Advantages of a pitched roof at a glance:
  • reduced CO2 emissions (up to 16%)
  • creation of additional space
  • freedom from maintenance
  • durability respective reusability of elements
  • lower lifecycle costs over 50 years (up to 16%)
  • lower production costs

Environmental influences
  • Wind & storm
    At a pitched roof, wind forces break at the ridge. The suction power on the downwind side is only little. Small-format roofing materials are easily lifted by wind and drop back into their original position. At a flat roof, on the contrary, the wind current applies behind the ridge and generates a negative pressure, which lifts roofs like the wing section of an aeroplane.
  • Increasing frequencies of extreme weather events, as a consequence of climate change, challenge building structures. The structural stability of pitched roofs, however, allows the roof to withstand heavy loads resulting from snow or hail. Steep pitched roofs don’t have to be freed from snow manually. Clay roof tiles achieve hail resistance class HW4 (Ø 40mm).
    Reference: Hagelprüfungen IBS Linz, 2014 (AT), http://www.hagelregister.at
  • Pitched roofs guarantee fast water drain, water runs “away” from and out of the building without any water barriers. So there is no risk of water damages. Easy and simple collection of usable rain water is possible.
    Reference: Lebenszyklus unterschiedlicher Dachkonstruktionen, Forschungsbereich für Industriebau und interdisziplinäre Bauplanung, TU Wien, 2014 (AT)
  • Sound protection
    Noise has a fundamental impact on the comfort in buildings; even more so in urban areas, where traffic can be dense. A well-designed and executed pitched roof provides excellent acoustic insulation thanks to its combination of sound-absorbing materials. A pitched roof allows the owners to sleep soundly even in heavy rainfall. 
    Reference: Lebenszyklus unterschiedlicher Dachkonstruktionen, Forschungsbereich für Industriebau und interdisziplinäre Bauplanung, TU Wien, 2014 (AT)
  • A pitched roof significantly improves the thermal efficiency of a building thanks to the natural ventilation underneath the top roof layer. This ensures optimal indoor comfort both in winter and summer.

Why has a pitched roof so many advantages?

Economic benefits
  • Costs
    The costs for the building component “roof” (roof cladding and sub-structure) are lower for a pitched roof regarding both the purchase price and over the lifecycle (50 years). Running expenses are also relatively constant. Only after a period of 30 years, the need of renovation arises.

  • Repairs
    The roof cladding materials can be replaced easily and without complications.
  • With pitched roofs, the subsequent creation of living space beneath the roof can be done without the need of elaborate and expensive annexes or attachments. By fitting skylights into a pitched roof, it will also be possible to let sunlight in and create a warm and light-filled living space under the roof.
    Reference: Lebenszyklus unterschiedlicher Dachkonstruktionen, Forschungsbereich für Industriebau und interdisziplinäre Bauplanung, TU Wien, 2014 (AT)
  • Power generation on the roof
    Photovoltaic & solar installations can be integrated into the roof surface area and adopt the function of the roof cladding.
    Reference: Lebenszyklus unterschiedlicher Dachkonstruktionen, Forschungsbereich für Industriebau und interdisziplinäre Bauplanung, TU Wien, 2014 (AT).
  • Environment
    As compared to a building with a flat roof, a house with a pitched roof saves approx. 26 tons of CO2 over a 50-year lifecycle. This equals 200,000 km travelled by car.

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