How much does underlayment cost?
Short answer. Underlayment is one of the cheaper layers of a roof, and its cost depends on type: asphalt felt is the least expensive, synthetic underlayment costs somewhat more but is lighter, stronger and more weather-resistant, and self-adhered ice and water barrier costs the most and is used in critical areas rather than everywhere. On a full replacement, upgrading underlayment adds relatively little to the total.
The types, from least to most expensive
- 15 lb and 30 lb asphalt felt. The traditional choice. Inexpensive, but it tears more easily, can wrinkle when wet, and degrades if left exposed.
- Synthetic underlayment. Woven or spun polypropylene or polyethylene. Tear-resistant, light, safer to walk on, and tolerant of longer exposure before shingles go on. Now the most common choice on Georgia reroofs.
- Self-adhered ice and water barrier. A rubberized asphalt membrane that sticks to the deck and seals around nails. Used in valleys, around chimneys, skylights and walls, at low-slope sections, and at eaves where the code or manufacturer requires it.
- High-temperature membranes. Self-adhered products rated for the heat under metal roofing.
Where underlayment cost shows up
Because underlayment goes on only when the old roof is off, its cost is part of a replacement price. On insurance estimates it may appear as its own line per square or be bundled into the shingle line. Ice and water barrier is often a separate line by the square foot or square.
Where it is worth spending more
- Valleys, which carry the most water on any roof.
- Around chimneys and along sidewalls.
- Low-slope sections between 2 and 4 in 12, where code requires double coverage or a membrane.
- Eaves on mountain homes prone to ice dams.
What to ask your roofer
Which underlayment brand and product will be used, where ice and water barrier goes, and whether those products qualify for the shingle manufacturer's system warranty. Compare options in synthetic underlayment vs felt and ice and water shield in Georgia.