GAF Underlayment & Deck Repair in San Antonio, TX

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

GAF underlayment and deck repair in San Antonio typically runs $1,800-$4,200 for a full section replacement, with most jobs completed in a single day using GAF-approved materials. We stock GAF FeltBuster synthetic underlayment, TigerPaw premium breathable underlayment, and CDX/plywood decking on every truck, and our crews carry the full GAF accessory catalog for same-day completion on standard repairs. Most San Antonio homeowners discover the problem after a hard rain: water stains spreading across the ceiling, shingles that look fine from the street but are riding on saturated, crumbling decking underneath.

Call (833) 756-5022

Which GAF Models This Applies To

GAF underlayment and decking aren’t tied to a single shingle line - they’re the foundation layer beneath Timberline HDZ, Timberline UHD, Timberline AS II, Royal Sovereign, and every other GAF system sold in San Antonio. What matters is matching the underlayment class to your existing roof assembly and local code. San Antonio falls under IRC 2018 with Texas amendments, which requires underlayment on all shingle roofs and ice barrier protection at eaves - though our freeze events are rare, the code stands.

Here’s how to identify what you’ve got: peel back a lifted shingle tab at the eave and look for the printed roll edge. FeltBuster shows a black synthetic weave with “GAF” repeat-printed; TigerPaw carries a gray non-woven surface with the paw logo. Traditional #15 felt is organic, tears easily when wet, and has no printed branding. For decking, we measure thickness at the roof edge - 7/16″ OSB was common in 1990s San Antonio builds, but 1/2″ or 5/8″ plywood holds fasteners better in our expansion-contraction cycles. We won’t install over rotted 7/16″ OSB; we’ll sister in proper 1/2″ CDX or full 5/8″ replacement per the span rating.

OEM GAF underlayment versus quality aftermarket: we use GAF-branded rolls for warranty-registered systems because GAF’s Golden Pledge and System Plus warranties require it. For older roofs out of warranty, we specify Polyglass TU Plus or similar ASTM D226/D4869 compliant synthetics that match GAF’s permeance and tear specs at a lower material cost - but we never substitute without writing it on the estimate. Cecil Hargrove makes that call personally on every job.

Signs Your GAF Underlayment & Deck Repair Is Failing

• Water stains on the ceiling that grow after every rain. The underlayment has torn at a valley or penetration, and water is running across the decking until it finds a joint. In San Antonio’s spring storm season, one compromised seam can channel gallons into your attic before the shingles ever show damage.
• Soft spots when you walk the roof, or visible sag between trusses. This is decking delamination - the glue in OSB or the plys in plywood have separated from repeated wet-dry cycles. Our summer heat bakes moisture into the attic, then a September thunderstorm soaks it again; that expansion and contraction destroys decking from underneath while shingles look intact.
• Shingle tabs that lift or crack in straight lines. When decking swells, it pushes nails upward; when it dries and shrinks, the nail pops slightly. The shingle fastener loses grip, and wind gets underneath. We see this pattern especially on north-facing slopes in Terrell Hills and Alamo Heights where morning dew lingers.
• Granules collecting in gutters but shingles appear aged evenly. The shingles aren’t failing - they’re sliding on a deck that’s too soft to hold fasteners. The nail heads work through the mat, granules wash free, and the real problem stays hidden until someone climbs up and presses a foot to the surface.
• Musty attic smell that peaks after rain, even without visible leaks. The underlayment is breathing moisture into the attic space instead of blocking it. GAF TigerPaw is designed to 16 perms; failed felt or torn synthetic spikes to 40+ perms, and humid attic air becomes a mold risk in San Antonio’s shoulder seasons.

Replacement Cost & What’s Included

What moves the price: deck accessibility (steep pitches in Monte Vista or Olmos Park add labor), how many sheets need replacement versus full redeck, and whether we’re matching existing GAF accessories or upgrading the system. We price by the square and by the sheet, not a mystery lump sum. The number on your estimate is the number on your invoice.

Every underlayment and deck repair carries our 90-Day Done Right Promise - written, no paperwork runaround, no arguing. If a seam lifts or a sheet squeaks, we come back and make it right. We’re also authorized GAF installers, so if your repair ties into a warranty-registered roof, we document with photos for your GAF file. We’re independent - not affiliated with GAF corporate - but we play by their rules when we’re protecting your coverage.

DIY or Call Us?

There’s an honest line here. A homeowner can safely check attic decking from inside - press a screwdriver to the rafter bays near stains; if it sinks past the tip, you’ve got rot. You can also photograph underlayment roll labels from a ladder if you’re comfortable at eave height. What we don’t recommend: walking a compromised deck, removing shingles to expose underlayment, or cutting decking without knowing rafter spacing. We’ve seen DIYers step through 3/8″ decking in Castle Hills and worse, fall through a rotted valley.

Deck repair means working at height on a surface that may not hold your weight. Our crews wear fall protection, carry pneumatic decking nailers that seat fasteners to manufacturer spec, and know which GAF underlayment overlaps require 4″ versus 6″ seams per slope pitch. The savings on a DIY underlayment swap rarely cover the emergency room visit. If you’re unsure, call (833) 756-5022 - a live person answers, and we’ll send a technician to photograph what you’ve got and talk through whether it’s a repair year or a replacement year.

FAQs