4 factors guarantee a 25-year service interval
When you renovate or build new, make sure you get a proper roof. If the roof is correctly designed and implemented, it will last the next 25 years without maintenance. Do these 4 things to make your roof last.
1. Don’t get fancy with the design
The designer should not get too fancy with the roof, but it should be as intact and unpretentious a whole as possible. Water, snow and any ice should be able to reach the ground safely through the force of gravity alone. This principle applies to all roofing materials, not just sheet metal. If the designer’s signature has to be put somewhere, they must know how to do it on the roof while respecting building physics and the laws of nature. Potential problems should not be created deliberately.
2. Choose a normally glossy roofing sheet
A high-quality, normally glossy painted roofing sheet requires little maintenance, even though manufacturers’ instructions often contain quite extensive lists of maintenance requirements. They are generally written because of warranty terms.
Snow and water wash a normally glossy sheet metal roof for free, and separate cleaning measures are hardly needed. The area around a chimney in use, from the chimney to the eaves, should sometimes be washed if you burn rubbish in the stove. And of course, the roof should otherwise be washed too if, for example, debris from trees accumulates on the roof or snow guards prevent the roof from being cleaned by falling snow.
If the paint surface of a sheet metal roof is so-called normally glossy (gloss 30-50), the lichen and moss growth typical of tile and felt roofs is fairly rare. Dull or matt-finished roofing sheets behave more like concrete tiles.
The dullness of the paint surface (matt-finished, fully matt) indicates that the surface is micro-rough, making it easy for impurities to stick to it. Water, snow or even a person may not necessarily be able to wash a matt-finished roofing sheet clean.
3. Use roofing screws that comply with regulations
There are many painted roofing screws manufactured by different suppliers on the market whose life cycle is not as long as that of roofing sheet metal. The problem is not so much the threaded body of the screw, for which 12 microns of electro-galvanising is sufficient if the roof does not leak and is properly ventilated.
The problem with screws currently in use is inadequate coating on the head, which does not correspond to the coating of the sheet metal being fastened. The heads of poorly coated screws exposed to the weather rust prematurely, and the screws must be replaced long before the sheet metal needs maintenance. Therefore, they do not meet building product regulations and are not approved, even though some manufacturers claim otherwise.
The use of stainless steel screws cannot be recommended on any roofs other than roofs made of stainless steel, and there are few of them. You can read more about the problems caused by stainless steel screws in the blog I wrote earlier.
When you use screws that comply with building regulations, you can be carefree for one generation.
4. Touch up scratches immediately
High-quality sheet metal does not rust if the paint surface has not been scratched down to the zinc. An intact, high-quality polyurethane-based paint surface lasts one generation without maintenance painting, generally considered to be 25 years. The thicker and more resistant to handling the paint coating is, the better it withstands both time and handling. The thicker the coating is for the climate to wear down, the longer the coating lasts. Quite logical. This, of course, assumes that the coating is not associated with any sudden death like PVC Plastisol, which I briefly discussed in the previous blog.
Sheet metal also does not rust from scratches if the scratches are properly touch-painted immediately after the scratch occurs, before they get dirty. Since scratches are more likely to occur during installation, it is worth investing in an inspection and touch-up painting after installation.
Scratch inspections and touch-up painting should be carried out every few years if people walk on the roof, for example to drop snow. Those who drop snow are a dangerous group for the durability of the roof, and unfortunately often for themselves as well.
Touch-up painting is easier if any scratch is easily visible. That is why the smartest sheet metal suppliers still use a fairly bright yellow, easily visible primer. The colour does come for free, though, if the market’s best corrosion inhibitor, strontium chromate, is used. Some sheet metal suppliers have switched to less distinguishable grey primers so that customers would get the impression of a product resistant to scratching. It is rather dishonest game, but it does increase sheet metal sales because of faster rusting.
The durability of the roof is therefore largely dictated during the design and installation stages. If the roof is designed to function rather than become a marvel of Cubist architecture, a good roofing sheet and roofing screws that comply with regulations are chosen, and the installation is commissioned from skilled installers, it is carefree to live under the roof.