When it comes to applying a metal shingle, slate or mechanically-fastened tile roof, you need an underlayment that will increase the protection of your investment. Fulfill that need with CertainTeed's MetaLayment. Clogged gutters, high winds and ice dams cause water to accumulate on lower sloped roofs which can cause damage. It is waterproof, does not rip and seals around nails driven through it. MetaLayment can combat these elements.