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I'm trying to choose between various roofing materials (cement tile, metal, asphalt shingles) for a re-roof, all of which come with certain guaranteed lifespans. But it is my general impression that it is the lifespan of the underlayment that governs the life of the roof. If the underlayment is brittle from age, then (as happens frequently here in rainy season), the roof is bound to leak regardless of the asthetic covering (tile, shingle, etc.). If the underlayment gets brittle at 15 years, it doesn't matter if the metal is guaranteed for 50, water will find its way in. Our 20 yr old cement tile roof is structurally sound, but the underlayment is now cracked and the roof is leaking and needs replacing entirely. Am I correct about the underlayment vs. roofing lifespan? Thanks in advance for your answer!
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Using concrete tile as an example, it is porous and absorbs water to up to 10% of its weight and as such this product relies on the underlayment to keep the roof weather tite. Same with wood shingles.
Underlayment serves two purposes. All these types of systems including th metal are "Hydro Kinetic" roof systems which rely on the downward and controlled movement of water to "shed" the water.
The underlayment is there to principally act as a condensation barrier however introduce severe wind driven rain and or ice daming and you could get also some backup of moisture into the system.
There are better longer life underlayments. Consult with your manufacturer.
7/24/2006
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7/25/2006
Or copy this URL: https://www.metalroofing.com/spirit/comment/8393/find/