GAF Underlayment & Deck Repair Nationwide

GAF Underlayment & Deck Repair: The San Antonio Owner’s Guide

If your GAF roof is leaking or showing signs of deck rot, you’re likely looking at underlayment or deck repair that typically runs $850 to $2,800 in San Antonio depending on how much decking needs replacement. We stock GAF-compatible underlayment and decking materials on our trucks and can usually start the repair within 24 to 48 hours of your call. Most San Antonio homeowners discover the problem after a heavy storm when water spots appear on the ceiling, or when a roofer doing a routine inspection finds soft decking beneath the shingles. The underlayment is the waterproof barrier between your shingles and the wood deck, and when it fails, the deck rots from the top down. Here’s exactly what to expect, what it costs, and how we fix it right the first time.

Call (361) 209-8857

Key Takeaways:

• GAF underlayment and deck repair in San Antonio typically runs $850 to $2,800 installed
• We write your price before any work starts: the number on the page is the number on the invoice
• Every repair is covered by our 365-Day Done Right Promise in writing, including a free second visit if the repair fails
• We stock GAF Deck-Armor, Tiger Paw, and FeltBuster products, plus quality decking materials, on our trucks
• Crestview Roofing Co San Antonio is an independent service provider, not affiliated with GAF

Which GAF Models This Applies To

GAF makes three main underlayment products you’ll find on San Antonio roofs, and each one pairs differently with specific shingle lines. GAF Deck-Armor is the premium breathable synthetic underlayment that goes under GAF Timberline HDZ, Timberline UHDZ, and Grand Sequoia shingles. It has a 50-year limited lifetime warranty when installed as part of a GAF system. GAF Tiger Paw is a high-grip synthetic underlayment designed for steep-slope applications, and FeltBuster is the synthetic option that replaced traditional 15-pound felt in most GAF system installs. If your roof is 10 to 15 years old and you have any of the Timberline series shingles, odds are one of these three products is what’s underneath.

One compatibility gotcha San Antonio homeowners should know: GAF’s system warranties only apply when the underlayment, shingles, and accessories are all installed together by a GAF-certified roofer. Mixing GAF shingles with an off-brand underlayment voids the system warranty even if the individual products perform fine. When we spec a repair, we match the underlayment to whatever GAF shingle line is on your roof: Timberline HDZ gets Deck-Armor or Tiger Paw depending on slope, and we document everything with photos so you have a record. For decks, we use CDX plywood or OSB rated for roofing that meets San Antonio building code, typically 7/16-inch to 5/8-inch depending on rafter spacing.

Signs Your GAF Underlayment & Deck Repair Is Failing

• Water stains on ceilings or walls: This is the most common first sign. Water penetrating the underlayment travels down the deck, follows a rafter, and drips at the lowest point, which is rarely directly under the leak.
• Soft or spongy spots when walking the roof: Rotted decking loses structural integrity. If a section of the roof feels like it bounces or gives slightly underfoot, the wood beneath the underlayment has likely been holding moisture for months or years.
• Granules in gutters paired with curling shingles: Shingle failure exposes the underlayment to direct UV and weather. Once the shingle barrier breaks down, the underlayment becomes the last line of defense and degrades faster.
• Visible sagging between rafters: On steep-slope sections typical of San Antonio ranches and two-story homes, a dip between rafters means the deck has lost rigidity. This is past a simple overlay: the section needs to be cut out and replaced.
• Mold or mildew odor in attic: Trapped moisture under a failing underlayment creates the warm, damp conditions where mold grows. San Antonio’s summer humidity accelerates this: a small leak can turn into full deck rot in a single season.

Replacement Cost & What’s Included

In San Antonio, underlayment and deck repair pricing breaks down into three bands. A small repair, one sheet of decking or less with underlayment replacement, typically runs $850 to $1,400. A mid-size repair covering a 10-foot by 10-foot section, usually a valley or a chimney area, runs $1,400 to $2,100. A larger repair with multiple deck sheets or a full roof-plane underlayment replacement runs $2,100 to $2,800 or more depending on square footage. Every quote includes labor, materials, disposal, and the written price before any work starts. No change orders, no “we found more damage once we opened it up” surprise.

What drives the range in San Antonio specifically: roof slope and access. Steep-slope roofs in areas like Alamo Heights or Terrell Hills take longer and require fall protection, which adds labor. Two-story homes add time. Deck replacement cost also depends on rafter spacing: homes built in the 1960s and 1970s often have 24-inch rafter spacing, which requires thicker 5/8-inch decking instead of the standard 7/16-inch, and that’s a real material cost difference. Every repair is covered by our 365-Day Done Right Promise in writing, included with every job.

DIY or Call Us?

What you can safely check yourself: look at your ceiling for water stains, check the attic for damp insulation or daylight showing through the deck, and clear your gutters so water drains properly. That’s diagnosis, not repair. What you should not do is strip shingles off your roof and replace decking yourself. Roof deck replacement means working at height, cutting out structural material, and reinstalling waterproofing that has to hold against San Antonio’s spring storms and 100-degreeAugust heat. One wrong step on a rotted section of deck and you’re through the attic ceiling. One misaligned underlayment seam and you’ve got a leak that rots the new deck within a year. This is the part of the roof system where a mistake compounds silently for years before you see it. Call (361) 209-8857 and we’ll get you a written quote the same day.

How Long Does GAF Underlayment Last in San Antonio?

GAF Deck-Armor and Tiger Paw are warrantied for 50 years in a system install, but real-world lifespan in San Antonio runs 25 to 30 years before replacement. That’s because San Antonio’s climate is harder on roofing than the national average: UV index spikes in summer, hail events in spring, and high humidity that keeps moisture against the underlayment longer than in drier climates. FeltBuster typically lasts 15 to 20 years in our market. The underlayment fails before the shingles will visually show it: by the time you see shingle damage, the underlayment beneath has often been compromised for years.

Can My GAF Underlayment Be Repaired Instead of Replaced?

If the failure is localized: a section around a nail pop, a small tear near a pipe boot, or a single sheet of rotted deck: yes, a repair is viable and we do them regularly in San Antonio. If the underlayment is failing across multiple roof planes or the deck rot spans more than 10% of the roof surface, patching creates weak seams and becomes more expensive long-term than a targeted replacement. We’ll show you photos of what we find and give you an honest recommendation. If a repair makes sense, the underlayment replacement for that section typically runs $500 to $900, and deck replacement adds $120 to $160 per 4-by-8 sheet depending on thickness. Call (361) 209-8857 for an exact quote after an inspection.

How Long Does the Swap Take?

Most underlayment and deck repairs in San Antonio take 1 to 2 days from start to finish. A single deck sheet with underlayment replacement is usually a same-day job when weather allows. Larger sections, multiple sheets, or steep-slope work can add a day. We show up with materials loaded based on your roof’s measurements, so there’s no trip back to the supply house mid-job. You’ll get before-and-after photos of the repaired section and a digital invoice texted to you when the work is done. Call (361) 209-8857 for an exact quote, and we’ll schedule your repair around the forecast.

Do You Stock GAF Underlayment & Decking on the Truck?

Yes. We stock GAF Deck-Armor, Tiger Paw, and FeltBuster on our service trucks, along with 7/16-inch and 5/8-inch CDX plywood and OSB decking rated for roofing. We also carry underlayment materials compatible with Owens Corning and CertainTeed systems when a roof has mixed-brand shingles, which happens more often than you’d think on San Antonio homes that had partial repairs done over the years. We’ll match the underlayment to your existing GAF shingle line and document the match with photos before and after the repair. Call (361) 209-8857 to schedule your free estimate.

Will the Price Change Once You Open the Roof?

No. Our written price is the price, and that’s the point of The Relay Visibility Guarantee. We measure, we quote, and we honor the number. If we open the roof and find more damage than the original scope, we stop, show you photos, and write a separate quote for the additional work before we touch it. You approve everything in writing before we proceed. Every promise we make goes in writing, because a handshake doesn’t keep water out. Call (361) 209-8857 for a free estimate and we’ll put the price on paper before any work starts.

Contact Crestview Roofing Co San Antonio for GAF Underlayment & Deck Repair

If your GAF roof is leaking, sagging, or showing signs of deck rot, call (361) 209-8857 and we’ll schedule a free estimate. You’ll get a written price before any work starts, before-and-after photo documentation, and a 365-Day Done Right Promise covering every repair in writing. A live person answers 24/7, so you won’t sit through a voicemail loop. We serve San Antonio and the surrounding communities, including Alamo Heights, Terrell Hills, Stone Oak, and the greater Bexar County area.

Written by Dylan Pace, Owner, Crestview Roofing Co San Antonio at Crestview Roofing Co San Antonio, serving San Antonio and nearby areas.