Service life
We have our assumptions about how long things should last. We hope that love would last forever and that the dishwasher would never break down. For many things, such as buildings, indicative service lives have been defined in industry standards (SFS-EN 1990+A1+AC). For example, residential buildings should last 50 years, and the fastening of a metal roof should last as long as the building.
Indicative design service life
| 15–30 | Agricultural and similar buildings |
| 50 | Residential buildings and other conventional structures |
| 100 | Monumental buildings and other civil engineering projects |
The best modern steel roofing materials last without maintenance for as long as 20–30 years if scratches caused during installation are immediately touched up with repair paint after installation. A sheet metal roof is also easy to repaint for maintenance, in which case the required 50 years is easily reached. With more extensive maintenance, a sheet metal roof can last as long as 100 years. This already requires roofing screws and other accessories to be just as durable as the roofing sheet.
When talking about building materials made of steel, the greatest threat to their durability is corrosion, or deterioration. Corrosion is generally understood as rusting, which can be seen with the naked eye. Corrosion can also cause changes in physical or mechanical properties that cannot be detected with the naked eye, such as a decrease in the metal’s toughness.