When people picture a roof, they picture shingles or metal panels — the part you can see from the street. But underneath that visible layer sits a material that does a huge amount of the actual work of keeping water out of a house: the underlayment. In Dallas, Fort Worth, Plano, Frisco, Arlington, Irving, McKinney, and the rest of North Texas, the underlayment layer takes a beating that most homeowners never think about until a hailstorm or a wind event exposes a weak spot. This page covers what underlayment actually is, how it holds up in our specific climate, and how the two common options — synthetic underlayment and asphalt-saturated felt — compare.
Roof underlayment is the water-resistant barrier installed directly on the roof deck, underneath the shingles, metal panels, or tile. It's not the primary waterproofing layer in the way homeowners often assume — shingles are meant to shed the vast majority of water — but it's the backup system that protects the plywood or OSB decking when wind drives rain up under a shingle tab, when ice or debris compromises a seam, or during the window between tear-off and re-roofing when the deck is exposed.
Two main families are used on North Texas roofs today. Asphalt-saturated felt, sold in 15 lb and 30 lb rolls, has been the standard for decades and is still installed on a lot of homes because it's inexpensive and familiar to many crews. Synthetic underlayment, made from woven or non-woven polypropylene or polyethylene with a coated surface, has become the more common choice on newer installs and re-roofs because it's lighter, tougher, and more consistent from roll to roll. A third product, self-adhered rubberized asphalt membrane, is typically used only in targeted areas — valleys, eaves, and around penetrations — rather than across the whole roof, because of its cost.
Underlayment choice matters more here than in milder climates because of what North Texas roofs are actually exposed to. This region sits inside what insurers and roofers sometimes call "hail alley" — the DFW metro sees some of the highest hail frequency in the country, and a severe hailstorm can crack, bruise, or fully dislodge shingles, temporarily leaving the underlayment as the only thing standing between the deck and the weather until repairs happen. A synthetic underlayment's higher tear strength and better resistance to UV exposure give it a real edge here: if shingles are compromised and a roof sits exposed for days or weeks waiting on insurance adjusters and material availability (common after a widespread hail event), synthetic holds up noticeably better than felt, which degrades faster with sun exposure and can wrinkle or tear underfoot.
Straight-line wind and the occasional derecho are the other major factor. North Texas gets fast-moving thunderstorm lines with wind gusts strong enough to lift shingle edges and drive rain sideways under them. Underlayment with a higher fastener-holding capacity and tighter overlaps reduces the odds of water tracking across the deck and reaching the interior ceiling. Felt, when it gets wet before shingles go over it — not unusual on a multi-day tear-off in unpredictable spring weather — can wrinkle permanently, creating a rippled surface that telegraphs through the finished roof and creates channels where wind-driven water can pool.
Then there's the heat. Summer roof deck temperatures in North Texas regularly exceed 150°F, and the daily swing between a scorching afternoon and a cooler night puts every roofing material through constant expansion and contraction — what roofers call thermal cycling. Felt becomes brittle faster under sustained heat exposure, especially if any part of it is exposed longer than intended during installation delays. Synthetic underlayments are generally rated for longer UV exposure windows (often 90 to 180 days depending on the product) and tolerate the heat cycling with less embrittlement over the life of the roof.
One more regional wrinkle: North Texas sits on expansive clay soil, and the foundation movement that follows wet-dry cycles can transmit subtle stress into the structure above, including roof framing. That movement doesn't destroy underlayment, but it's one more reason to use a product with some flexibility and tear resistance rather than the most brittle option available.
Synthetic underlayment's advantages are real: it's lighter (easier and safer to carry up a ladder and across a hot roof), stronger against tearing, more slip-resistant when installers are walking the deck, and more tolerant of sun and moisture exposure during construction delays. The downside is cost — synthetic typically runs somewhat more per square than felt, and on a full re-roof that difference adds up, though it's usually a modest fraction of total project cost.
Felt's real advantage is upfront price and long-established familiarity — most roofing crews have installed it for years and know its quirks. Its downsides are the ones described above: faster UV degradation, wrinkling when wet, and lower tear strength. Felt isn't a bad product when installed correctly and covered promptly, but it leaves less margin for the kind of installation delays and severe weather that are common here.
Underlayment isn't a serviceable component on its own — it's not something you maintain the way you'd clean gutters or trim tree limbs. Its practical lifespan is tied to the roofing system above it. A properly installed synthetic underlayment under asphalt shingles will generally outlast the shingles themselves, which typically run 20 to 30 years in this climate depending on product quality and hail exposure. Felt's functional life under an intact shingle roof is similar, since it's shielded from UV once shingles are on, but if a roof section loses shingles in a storm, felt degrades within weeks of direct exposure while synthetic buys more time. The real maintenance point is indirect: keeping the shingle layer intact through timely hail and wind-damage repairs is what protects the underlayment underneath it. When Alpine Exteriors inspects a roof after a storm, we're often checking whether the underlayment is still doing its job even where shingles were damaged.
For most North Texas homeowners, the practical decision is synthetic versus felt on a re-roof, since that's the choice made at installation and rarely revisited afterward. Felt remains code-compliant and is still a workable choice on a budget-conscious project, particularly on a roof less exposed to hail (steeper pitches, less tree cover) or where the homeowner plans a shorter ownership horizon. Synthetic is the stronger choice where hail exposure is significant, where a roof might sit partially exposed during a storm-driven repair queue, or where the homeowner wants the added margin during the roof's working life. Neither product is a waterproofing guarantee by itself — proper installation, correct overlaps, and quality shingles above it matter as much as which underlayment is chosen.
Underlayment alone typically isn't what insurers price into wind/hail premiums or deductibles — that's driven more by the shingle or panel class (impact-resistant Class 4 products can sometimes qualify for a discount) and by the overall roof condition. That said, a roof with quality underlayment is less likely to suffer interior water damage after a hail event, which can matter at claim time.
No — underlayment sits under the entire shingle or panel field, so replacing it requires removing what's above it. It's addressed as part of a re-roof, not as a standalone repair.
Given how much hail and wind North Texas sees, we generally recommend it, but it's a legitimate trade-off decision — felt is still a functional, code-approved product, and the price gap is usually smaller than homeowners expect relative to total project cost.
We use self-adhered membrane selectively in valleys and around penetrations on many roofs, not as a full-roof product — it's less about ice here and more about giving vulnerable, high-water-flow areas extra protection against wind-driven rain.
If your roof is due for replacement, or you're not sure what's happening underneath your shingles after a recent storm, Alpine Exteriors can inspect the deck and underlayment condition and walk you through the honest trade-offs for your specific roof and budget. We serve homeowners across Dallas, Fort Worth, Plano, Frisco, Arlington, Irving, McKinney, and Denton. Contact us for a straightforward roof assessment.