Underlayment is the layer between your roof decking and your shingles. You never see it once the roof is done, but it is your roof's backup defense against water. If wind lifts a shingle or rain blows sideways, the underlayment is what keeps water out of your attic.
Felt Underlayment
Felt, sometimes called tar paper, has been used for decades. It is made from a paper or fiberglass mat saturated with asphalt. It comes in two common weights, often called #15 and #30.
- Pros: lower cost, familiar to every roofer.
- Cons: heavier, tears more easily, can wrinkle when wet, and can dry out and become brittle in high heat. Felt should not be left exposed for long before shingles go on.
Synthetic Underlayment
Synthetic underlayment is made from woven or spun polymers like polypropylene or polyethylene. It has become the standard on most new roofs.
- Pros: much stronger and more tear-resistant, lighter, lies flat without wrinkling, offers better water resistance, and holds up better if left exposed for a short time.
- Cons: costs more than felt. Some products can be slippery to walk on, especially when wet or dusty, though many have textured surfaces.
Ice and Water Shield
This is a separate product: a self-adhering rubberized membrane that seals around nails. In Houston, it is commonly used in valleys, around chimneys, skylights, and pipe penetrations, and along low-slope areas, where leaks are most likely. Some roofers also use it along the eaves.
Which Is Better for Houston?
For most Houston homes, synthetic underlayment is the better choice. It stands up to high attic temperatures, resists tearing during installation, and protects better if a storm rolls in before the shingles are finished. Many shingle manufacturers' upgraded warranties also require their own synthetic underlayment as part of a complete system.
What to Ask Your Roofer
- What underlayment are you using, and what brand?
- Where will you install ice and water shield?
- Does the underlayment meet the shingle manufacturer's warranty requirements?
If an estimate does not mention underlayment at all, ask. See how to read a roofing estimate.
JD Roofing Solutions uses quality synthetic underlayment on our roof replacements. See our Products & Brands page or call 832-295-3277.
