The primary guarantee is provided by the material supplier.
Depending on application, Tata Steel Colorcoat® branded products (Colorcoat Prisma® and Colorcoat HPS200 Ultra®) are available with either the Confidex® Guarantee (for industrial and commercial projects) or Confidex® Home Guarantee. This is the market leading pre-finished steel guarantee.
SSAB offers a more general guarantee with their pre-finished steel products.
Depending on the location and application, good quality pre-finished steel products can have a 50 year life span. Tata Steel talks about period to repaint decision, which effectively means if the steel roof is repainted at specified intervals (usually every 25 years or more) it should last forever.
A workmanship guarantee is available from the installer and Vertix® Systems recommends customers asking for an insurance backed guarantee. Alternatively, you can get a latent defect insurance policy for the whole building. NHBC or Premier are providers of such insurance policies.