Bratex modular roof tiles part 1

.First Bratex modular metal roof tile was launched in 2015 under the Scandinavia product brand. What is the concept of a modular product?.

The overall concept of the product is based on:

• a properly constructed product that solves the known problems of conventional metal roof tiles,
• short sheets of metal roof tiles, so that they can be easily moved,
• delivery of the product on a euro pallet, so that loading can be carried out even in a passenger car with a cargo space,
• product packaging in the form of polystyrene spacers, which divide the batches into layers of about 120 kg,
• sheets with the repetition of shades to obtain the same shade on the roof after purchasing the missing sheets.

Bratex Scandinavia modular metal roof tile

Scandinavia modular roof tile belongs to the group of system metal roofing tiles that have features and solutions unavailable for ordinary conventional metal roofing tiles, such as:

• durability,
• technical correctness,
• functionality,
• aesthetics.

Steel as the most important construction material

Steel is the most important construction material on Earth. Steel sheet (so-called steel core) for roofing is first protected on both sides with zinc and varnished to ensure its durability and aesthetics.

On the top side of the metal sheet, a primer and decorative varnish with a total thickness of 25-50 microns are used, of various durability, quality and technology.

On the underside of the sheet, an ordinary epoxy varnish with a thickness of 10-12 microns is used, the purpose of which is to protect the underside zinc coating from the formation of zinc hydroxide stains when the product becomes damp or wet. Epoxy varnish does not protect the material against the external environment (susceptibility to degradation, UV radiation, aggressive chemical compounds).

Sheet metal construction layers

That is why the basic issue regarding maintaining the good condition of the metal sheet is to ensure free drainage of water, regardless of whether it is a metal roof tile or a gutter system.

Ordinary conventional metal roof tiles are cut to any length (up to 7-8 meters long). Such a sales model allows, in most cases, to lay one sheet along the entire length of the rafters and thus there is no transverse connection of the sheets. The exceptions are roof penetrations, i.e. chimneys or windows, in which a transverse connection must appear. Conventional metal roof tiles are cut with a straight knife, similarly to trapezoidal sheet. The vertical and horizontal profile of the knife (height and width) is adapted to the wave shape of the metal roofing tile. The beginning of the sheet before the first embossing is usually about 3 cm long.

There are also metal tiles called "modular", but not having the characteristics of a modular product, which are offered in short sheets and cut along the wave with a shaped knife (sometimes called a 3D knife, i.e. three dimensions: height, width and depth). Unfortunately, in most cases, just before the first embossing of the sheet, there is also a beginning of 3-5 mm.

The beginning of the sheet, whether it is 3 mm or 3 cm long, is where the water is capillary drawn when there is a transverse connection. If the roof is covered with, for example, two hundred sheets, there are 200 potential places where water with impurities is sucked.

The main issue to consider with roofing consisting of cross-joined sheets is their resistance to weather conditions. The context of durability does not refer to the quality of the material used for production, but to the technical solutions used in the roofing sheet.

The problem of rainwater retention

The key issue for us was to solve the problem of capillary suction of rainwater between the transverse joints of the sheets. Many roofs in Poland, even those in the vicinity of the building on which the modular metal roof tile was installed, are heated by burning coal or wood. Combustion products of these fuels, after escaping through the chimney, settle on the roof slope, as well as on the adjacent roofs, these are aggressive sulfur compounds. Then, during rain and wind, a mixture of water and aggressive sulfur compounds gets between the joints of the metal roof tiles.

In the case of longitudinal connections (from the bottom of the roof, i.e. the eaves to the top of the roof, i.e. the ridge), water suction usually does not occur, because the connections are well fitted and water does not get into this space, and even if the sheets have retention grooves, through which water can flow. Capillary grooves are also present, their function is to stop water from being drawn in.

At transverse connections (the line of overlapping the upper sheet with the lower one) of conventional metal roofing tiles and roofing tiles called "modular", water with impurities gets between the connections due to the capillary suction of water. The phenomenon can be compared to dripping water on a slide and partially applying another slide to it. The rising of the applied water and its distribution on the surface will be observed. This phenomenon occurs if we do not stop the rising water.

It depends on the design and solutions of the modular metal roof tile whether water with impurities will remain between the sheets of the metal roof tile or will flow out freely. Residual water with impurities between the sheets starts the degradation of the underside of the sheet protected with ordinary epoxy varnish.

Our company already at the beginning of 2013 together with the technical laboratory of the steelworks SSAB in Sweden, has started research into designing a solution that eliminates the risk of capillary suction of water and impurities when the sheets are joined crosswise. One of the stages was the analysis of hundreds of sheet metal samples at the Bohus-Malmön research station. The station was built more than 40 years ago and thousands of samples have been exposed in this area, exposed to the aggressive effects of the marine environment and partly to UV radiation.

The analysis of water flow behavior, technical possibilities of production and the obtained functional features of the product led to the design of a breakthrough solution for metal roof tiles.

Bratex Anti-Cap is a feature of all Bratex system metal roofing tiles, which fully solves the problem of capillary suction of water between the transverse joints of the sheets, which occurs in conventional metal roofing tiles and in the so-called "modular" metal roofing tiles.

Bratex Anti-Cap is a structure of the first embossing of a metal roofing tile with the following characteristics, which together make up the final effect:

1. The first embossing is cut along the wave and instead of the beginning it has the so-called dripping edge preventing the rising and retreating (at low roof slopes) of water flowing down between the sheet joints.
2. The first rib is 2 millimeters lower than the other ribs. System modular metal roof tiles have a nominal embossment with a height of 35 mm, and hybrid 30 mm. Thus, the first Bratex Anti-Cap rib has a height of 33 and 28 mm, respectively. With such proportions, the upper sheet that covers the lower sheet does not create conditions for capillary suction of water with impurities and for its retention between the sheets.
3. The first embossing is tilted a few degrees towards the roof slope, creating a ventilation space at the connection point. The ventilation space ensures that during a downpour and wind, every drop of water with impurities that gets between the transverse joints of the sheets will flow out and the transverse connection will be ventilated. In addition, the deflected first rib ensures the outflow of condensed water vapor on the underside of the sheets, the drops of which did not fall on the membrane and got between the ribs of the sheets (between the transverse connection).

Bratex Anti-Cap

Bratex Anti-Cap means maintaining the best condition of system sheets of metal roof tiles, because:

• prevents water from being sucked between the sheets,
• prevents water stagnation between the ribs,
• provides ventilation of transverse overlaps.

Thus, Bratex Ant-Cap is part of the warranty, not only issued by the roof tile manufacturer, but also by the steelworks, and this applies only to the manufacturer, one of the always present conditions of which is "ensuring free water outflow".

Presentation of further features of our system modular metal roof tiles i hybrid we will present in the next articles.