Consider installing felt under a metal roof

Metal roof tiles: classic look - modern material

Large-volume steel roof tile elements enable quick assembly.
Photo: Luxmetall

When it comes to metal roofs, one first thinks of large sheet metal elements with a trapezoidal profile or standing seam design. But small-scale optics are now also possible: with roof tile sheets that are shaped like classic roof tiles.

The advantage of such steel or aluminum roof tiles compared to conventional clay or concrete products is primarily the very low weight of the metal roofing. The sheets, which are usually only 0.5 mm thick, weigh about 5 kg per square meter on the roof structure. According to the action group for steel roofing tiles, concrete or clay roofing products weigh ten times as much in the same area.

Weight advantages

The low weight is an advantage above all if you want to energetically renovate existing roofs with over-rafter insulation. Often the old roof trusses are not resilient enough to support thick layers of insulation in addition to the roofing. So they would have to be reinforced or completely renewed at great expense. This can often be avoided with roof tiles made of steel - or the even lighter aluminum. The additional weight of the insulation material is compensated for by the light covering. The builder can look forward to an insulated roof with a classic pan look - just made of metal. It is even easier if the existing building to be renovated has a lightweight old roofing - made of bitumen or fiber cement, for example. Then insulation and metal roof tiles can often even be applied directly to the existing roof.

Price level

Roof-on-roof installation saves time and money because the old roofing does not have to be removed and disposed of. Speaking of costs: The bottom line is that the use of metal roof tiles usually saves money, but that does not mean that the material itself is fundamentally cheaper than concrete roof tiles or clay tiles. It is difficult to say in general about the prices, especially since the differences depend not only on the material, but also, for example, on the manufacturer's brand, the type of roof tile (different sizes and areas of application, with or without a fold) or the surface coating (colors, engobes, glaze, Protective layers). If one compares roof tiles of the same type, it can be put simply that the steel products are usually a little more expensive than concrete pans and a little cheaper than clay tiles. Aluminum pans, on the other hand, are more expensive than steel products.

Material properties

Multi-layer structure of a steel roof tile made by Luxmetall.
Graphics: Luxmetall

Metallic roof tiles are not only light but also very durable. This applies in particular to the metal aluminum, which does not rust. But the steel profiles are also galvanized and are therefore corrosion-resistant. In any case, the metal core never gets onto the roof unprotected. Regardless of whether steel or aluminum: The pans are always protected by a multi-layer surface finish (see graphic). The outer layer usually consists of weather-resistant polyester plastic and is available in a wide variety of colors - both in matt and glossy versions. The surface is usually very smooth. This has the advantage that dirt, but also moss and lichen hardly find a hold on the metal roof tiles.

Possible drawbacks

Steel and aluminum are “cold” materials with high thermal conductivity. So they are less heat-insulating than clay or concrete. However, this disadvantage is hardly significant if insulation materials are already installed below the roofing. The thermal insulation that is common today also ensures that another alleged disadvantage of metal roofs has lost its importance: In rain or hail, the resulting drum noises on the roof skin are certainly louder than on clay or concrete roof tiles, but the insulation layer not only protects against heat loss, but also attenuates the sound transmission inside the building.

There are also solutions for the frequently discussed problem of condensation water. It is clear that water vapor condenses relatively quickly on a cool metal surface. It is particularly problematic if a dripping film of moisture forms on the underside of the roof tiles. To counteract moisture problems, roof coverings must be ventilated. DIN 41083 prescribes a ventilation cross-section of at least 2 cm between the roof tiles and the insulation or the underlay. This is to ensure that moisture is quickly removed from the roof structure. In addition, the industry also offers special metal roof tiles, which are coated on the underside with a water-absorbing felt material.

processing

In addition to their low weight, the greatest advantage of modern metal roof tile systems is that they are very easy and quick to assemble. The industry offers pan trays up to eight meters in length, which can be easily cut to size as required. The width of the elements is about one meter. In other words: the roofer does not have to lay each pan individually, but can achieve very rapid work progress with the large-volume sheets.

Metal roof tiles do not require their own substructure. They can easily be attached to the existing roof structure. In contrast to clay tiles or concrete roof tiles, however, they are firmly screwed to the rafters and battens. This is possible because the metal sheets cannot break even under higher wind loads. So you can say that metal roof tiles are particularly storm-proof.


You can find more on the subject of roofs in the overview


About the author Roland Grimm has been a freelance journalist based in Essen since February 2013 and regularly writes specialist articles for Building material knowledge. Before that, he was a specialist editor at the industry magazine for around six years Building materials market and also editor-in-chief and, from 2010, editor-in-chief of the trade journal building materials practice. Contact: freelance [email protected]

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