Basically, the tile on your roof is a major defense against the elements, but the
underlayments also play a crucial role. They provide a secondary level of protection directly on top of your roof deck. Underlayments can provide longevity and improve the performance of your roof, so you want to make sure you choose the correct type for your roof.
There are a variety of “peel and stick” roofing underlayments available on the market now.
To name just a few of the benefits of using them rather than #30 felt or #90 slate are:
No smelly hot asphalt is used
Cleaner to install
Offers a slip resistant surface