IKO Underlayment & Deck Repair Nationwide

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

We stock and install IKO-compatible underlayment and decking repair materials across San Antonio, with most deck repair and underlayment replacement jobs running between $450 and $1,800 depending on how much of the roof deck has failed. The work typically takes one to two days once we expose the damaged area. Most San Antonio homeowners discover they have an underlayment or deck problem two ways: either through a ceiling stain that appears after a heavy spring storm, or when a different roofing crew lifts shingles for an unrelated repair and finds the decking underneath has started to rot.

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What catches people off guard is how far the damage can travel before it shows up inside the house. Water gets past the shingles, soaks into the underlayment, and sits against the OSB or plywood deck. By the time a stain appears on the ceiling drywall, the deck in that area is usually past the point where you can just patch the top layer. In San Antonio’s climate, where we get intense UV exposure, long dry stretches followed by sudden downpours, and plenty of wind-driven rain, underlayment failure tends to accelerate faster than in milder climates. The freeze-thaw we occasionally get in winter stresses seams too.

Key Takeaways:

• IKO underlayment failures almost always show up first as deck rot, not as visible shingle damage.
• Most San Antonio repairs range $450 – $1,800 installed, with a written price before we start.
• We stock synthetic underlayment and decking materials on the truck that are compatible with IKO systems.
• Every repair carries our 365-Day Done Right Promise in writing.

Which IKO Models This Applies To

IKO’s underlayment line spans several products that show up across different roof systems: Armourbase, StormShield, GoldShield, and their standard 15-pound and 30-pound felt. In San Antonio, the most common IKO underlayment we find on existing roofs is either a basic felt product on older homes or Armourbase synthetic on homes reroofed in the last 15 years or so. The decking underneath is usually CDX plywood or OSB, and IKO’s system requirements specify a minimum deck thickness of 3/8-inch plywood or 7/16-inch OSB for most shingle applications.

Here’s the compatibility gotcha most people don’t know: IKO’s warranty documentation requires the underlayment to match the shingle system’s wind and fastener specifications, not just be “roofing felt.” If a previous roofer laid standard felt under an IKO shingle system that called for Armourbase or StormShield, you can end up with a warranty gap and premature underlayment breakdown. We see this regularly in San Antonio neighborhoods like Alamo Heights and Terrell Hills, where homes built in the 80s and 90s have had multiple patch jobs over the years, each one potentially using whatever underlayment happened to be on the truck that day.

When we repair decking and underlayment on an IKO roof, we match the repair to what IKO’s system calls for, not just what’s cheapest to lay down. For older IKO felt systems, a quality 30-pound felt can be a correct match. For newer synthetic systems like Armourbase, we use an IKO-compatible synthetic underlayment so the repair area performs the same as the surrounding roof. Aftermarket equivalents are perfectly fine here as long as they meet the same ASTM standards and don’t void the shingle warranty. We stock both felt and synthetic on our trucks, so the decision is made based on what’s actually on the roof, not what we feel like selling that day.

Signs Your IKO Underlayment & Deck Repair Is Failing

• Water stains on ceilings or walls after rain. This is the most common first sign. It means water has already penetrated the underlayment and is traveling along the deck before finding a gap in the ceiling. By now the deck under that spot is almost certainly compromised.
• Spongy or soft spots when walked on. If the roof feels like it gives underfoot, the deck has lost structural integrity. OSB in particular swells and delaminates once it gets wet, and it never regains strength after drying.
• Shingles lifting or curling at the edges in one concentrated area. When IKO shingles lose their bond in a specific zone but not across the whole roof, it’s often because the underlayment beneath has wrinkled or the deck has moved due to moisture. The shingles are the symptom, not the cause.
• Granules collecting in gutters unusually fast. IKO shingles shed granules as they age, but when the underlayment below has failed and allowed trapped moisture, the shingles degrade from the underside too, accelerating granule loss. You’ll see it concentrated near ridges and valleys.
• Musty attic smell or visible mold on the underside of the decking. If you go into the attic after a rain and the underside of the roof deck looks dark or stained, the underlayment is no longer keeping moisture out. This is the clearest sign that the repair needs to happen now, not next season.

Replacement Cost & What’s Included

For San Antonio homes, IKO-compatible underlayment replacement with deck repair typically runs between $450 and $1,800 installed. The range is driven by how many sheets of decking need to come out and how much underlayment has to be peeled back and replaced to meet code overlap requirements. A simple underlayment patch with no deck replacement runs on the lower end, around $450 to $700. A larger deck failure where we’re replacing multiple sheets of OSB or plywood, installing new underlayment with proper overlap, and then re-installing IKO shingles to match runs $1,200 to $1,800 or more if the damage is extensive.

Every quote we give is a written price before we start, and the number on that page is the number on the invoice. No change orders for “unexpected rot” after we’ve already opened the roof, and no material upcharges once we’re on site. The labor and materials are itemized. Our 365-Day Done Right Promise covers the repair for a full year in writing: if anything fails within 365 days, we come back and fix it at no charge, no negotiation.

DIY or Call Us?

You can safely check a few things from the attic side without getting on the roof. Look at the underside of the decking with a flashlight after a hard rain. Press on suspicious spots. If the OSB or plywood has dark staining or feels soft, you have your answer. That’s worth knowing before you call anyone, because it tells you the repair is real and not just a shingle issue.

What you should not do is pull up IKO shingles and start cutting out underlayment yourself. The moment you lift shingles around a damaged section, you’re exposing the roof system to water intrusion if you don’t get it sealed back correctly the same day. Underlayment overlaps have code requirements in San Antonio, and getting them wrong creates a leak path that’s worse than what you started with. Deck repair means cutting structural material and fastening it to spec. And any roof work on a San Antonio steep-slope home carries serious fall risk. This is one of those jobs where watching a few videos doesn’t get you close to code. If you’d rather have us look at it, call (361) 209-8857 and we’ll give you a written estimate before anything happens.

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