Detect And Eliminate Hail Damage

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-11-26 11:39

When the second heavy hailstorm swept across Lossburg and the surrounding area in 2015, painter Jürgen Rehfuss from Loßburg-Betzweiler was clear: "That is causing trouble!" Has the same wooden windows and facades been caught again as two years ago? The premonition was confirmed a few days later. The hail damage was considerable.

Bernhard Linck

A wooden facade was particularly remembered. The storm had swept over the apartment building, damaged one side of the facade by hailstorms, then turned and worked two more sides. "It looked like sandblasted, the hail must have come down so thickly and violently," recalls Jürgen Rehfuss. The damage to this facade alone amounted to 14,000 euros.

If insurance policies were still accommodating in 2014 after the first hail event, things looked different in 2015. Now we took a closer look, depending on the age of the components, there were deductions. In one case, the customer was even terminated after repeated damage. In total, in 2013 and 2015 alone 80 customers of the Rehfuss painting company were affected by the hailstorm, with only two damage to plastered facades, with all the others suffering from wooden components. "So of course you get plenty of experience in recognizing and eliminating hail damage," reports Rehfuss. "Here in the Black Forest we have a reasonable fear of hail. Hail-resistant wooden surfaces and coatings would therefore be very welcome,”the master painter continued.

Although the Black Forest region is particularly prone to hailstorms due to its geographical location, the experiences of Rehfuss are not an isolated case nationwide. Hail damage is increasing not only on motor vehicles, but also on buildings. At the end of July and the beginning of August 2013, several hailstorms in Lower Saxony and Baden-Württemberg resulted in losses that had not previously occurred on this scale. According to estimates by the Gesamtverband der Deutschen Versicherungswirtschaft eV (GDV), this was 2.7 billion euros - more than the record floods in 2002 and 2013 or the hurricane Kyrill caused in 2007. (Source: Climate Service Center Germany)

find solutions

For the Deutsche Amphibolin-Werke (DAW), this is reason enough to find solutions for coated wooden surfaces in cooperation with other coating material manufacturers and renowned research institutes. The head of the research project "Hail-resistant wood coatings" has Gerhard Grüll from Holzforschung Austria.

He defines the objective as follows: “Together we are looking for solutions for the 'coating and wood' system to improve hail resistance. This is not just limited to the coating, but also to the wood surface itself. This should also be optimized so that an overall better hail resistance is achieved.

Classification

In contrast to Germany, there is a hail register in Switzerland and Austria. It classifies building materials with regard to their resistance to hail. The classification is based on bombarding the surfaces with a hail gun. Ice balls with a diameter of 10 to 50 millimeters are shot onto the surface of the building material. The facade materials are fired at a 45 degree angle. The result is classified in hail resistance classes from 1 to 5 (HW 1 - 5). The value HW 3 means, for example, that the surface survives a bombardment with an ice ball with a diameter of 30 millimeters without damage. There is therefore a recognized method for simulating and evaluating hail damage in these countries. The research project intends to build on this.

However, it is not quite that simple: the method is certainly a suitable method for roof tiles. But does it also provide differentiated results for the development of coating materials on wood? There are currently still discussions about whether and how this method can really be used in practice for wooden surfaces. The varied building material with its different surface hardness and the inhomogeneous structure of early and late wood has its pitfalls. Fortunately, one can assume that a laboratory-made ice cream scoop is a test size comparable to a hailstone. A realistic impact energy can also be calculated using an existing formula. However, the practical surface temperature at the time of the bombardment can already be discussed again. In addition, the process is very complex and hardly suitable for everyday development work in the paint manufacturers' laboratories. A simpler test method is also needed. In this way, one wants to judge at the laboratory stage whether shelling with the ice cannon in a test institute is promising. There are experiments with falling balls and pushing devices, always striving to get as close as possible to the “natural event of hail”.to get as close as possible to the “natural event of hail”.to get as close as possible to the “natural event of hail”.

Detect the damage

What is hail damage anyway? At first it mostly shows up on wooden surfaces as a dent with a circular crack in the coating. In the months after, graying and blue staining occur at the impact point due to water ingress. But even a dent without a cracked coating or consequential damage can already be a defect in terms of insurance. Who likes a window with the surface of a golf ball? The term “hail-resistant” must therefore be defined even more precisely for wooden surfaces. Ideally, there should be no dent from the hailstones. Solutions for this can be constructive measures such as aluminum covers, for example on the horizontal surfaces of windows. This is already standard for newer windows, but can also be retrofitted for older windows. In addition, the forward-looking selection of harder types of wood in particularly vulnerable areas, at high altitudes or on unprotected sides of the building should be taken into account. Oak is much more resistant than pine and spruce. These are certainly effective, but only complementary measures. Therefore, one of the objectives of the project is to modify the wooden surface to a higher surface hardness. But special impregnations to reduce water absorption are also being tested. This is intended to prevent consequential damage. For this reason, extensive laboratory tests and outdoor exposure with various processes and products are currently being carried out. Oak is much more resistant than pine and spruce. These are certainly effective, but only complementary measures. Therefore, one of the objectives of the project is to modify the wooden surface to a higher surface hardness. But special impregnations to reduce water absorption are also being tested. This is intended to prevent consequential damage. For this reason, extensive laboratory tests and outdoor exposure with various processes and products are currently being carried out. Oak is much more resistant than pine and spruce. These are certainly effective, but only complementary measures. Therefore, one of the objectives of the project is to modify the wooden surface to a higher surface hardness. But special impregnations to reduce water absorption are also being tested. This is intended to prevent consequential damage. For this reason, extensive laboratory tests and outdoor exposure with various processes and products are currently being carried out. For this reason, extensive laboratory tests and outdoor exposure with various processes and products are currently being carried out. For this reason, extensive laboratory tests and outdoor exposure with various processes and products are currently being carried out.

At the very beginning

Basic research is still carried out here as well. However, it is already agreed that acrylic dispersion coatings are more suitable than alkyd resins due to their better elasticity or impact resistance. These become increasingly harder over the years as a result of post-crosslinking and are therefore more brittle. Thick-layered, elastic coatings are generally better armed against hailstorms than thin-film glazes. But they have other physical advantages. You won't be able to sacrifice all other important properties to hail resistance. In the end, a reasonable compromise will bring the solution. These could be specially equipped coating films that are reinforced with nano-cellulose fibers and / or equipped with microcapsules. This is also currently being experimented with. These thousandths of a millimeter capsules in the coating film break open when they hit a hailstone and release an impregnating liquid at the point of injury. However, it is also conceivable for post-crosslinking substances to escape, which "self-heal" the coating film at the damaged area. Of course, this has to happen in the right place at the right time. Work is currently ongoing on this. The research project "Resistance to wood coatings against hail" is still at an early stage. However, there are already promising approaches that give hope that coated wooden components will become largely hail-resistant or at least more hail-resistant in the not too distant future.