How long does roof underlayment last?
Short answer. Covered by shingles or metal, roof underlayment generally lasts as long as the roof above it, about 20 to 30 years on a Georgia architectural shingle roof and longer under metal when a quality synthetic or high-temperature membrane is used. Under tile, the underlayment often wears out before the tile does, and uncovered underlayment lasts only as long as its sun exposure rating, which ranges from days for felt to months for many synthetics.
By type
- Asphalt felt: fine under shingles when covered quickly; dries out and wrinkles when exposed.
- Synthetic: woven or spunbond plastic sheets that are tear resistant, lighter, and usually rated for weeks to months of sun exposure. Check the label.
- Self-adhered membrane: rubberized asphalt or butyl sheets that seal around nails. Used at eaves, valleys and penetrations, or over a whole roof as a premium detail. High-temperature versions are made for metal and tile.
Under different roofs
Shingles: the underlayment is replaced along with the shingles, so it rarely becomes the weak link if it was installed well.
Metal: metal can outlast cheap underlayment, and heat under dark panels is intense, so high-temperature synthetics or membranes are the usual choice for a long-life roof.
Tile: tile can last 50 years or more, while felt beneath it often needs replacing far sooner. A lift-and-relay restores the underlayment and reuses the tile.
What shortens its life
- Long exposure before the roof covering goes on.
- Flashing leaks that keep it wet.
- Attic condensation wetting the deck from below.
- Wrinkles and tears from foot traffic during installation.
When it gets replaced
On a shingle roof, underlayment is not replaced by itself. When shingles are replaced, fresh underlayment goes on with them over the repaired deck; reusing the old layer is not good practice. See synthetic underlayment vs felt and ice and water shield in Georgia.