IKO Underlayment & Deck Repair Nationwide

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

If your IKO shingles are buckling, leaking, or showing dark stains at the eaves, the problem usually isn’t the shingle itself – it’s what’s underneath. We stock and install IKO-compatible underlayment and deck repair materials across San Antonio, with most deck repairs running $850 – $2,400 depending on how much sheathing has to come out and whether we’re replacing the underlayment at the same time. Same-day deck assessment is standard for us. The giveaway is almost always visible from the attic: water staining on the plywood, soft spots you can feel, or daylight showing through the roof deck.

Call (254) 276-4369

What surprises most San Antonio homeowners is how fast a small underlayment tear becomes a deck problem. The underlayment is the waterproof membrane between your IKO shingles and the plywood deck. When it fails – usually from age, a bad seam, or storm-driven rain getting under the shingles – water sits on the deck. In San Antonio’s heat-and-pour cycles, that trapped moisture rots plywood faster than people expect. By the time you see a stain on the ceiling, the deck under that spot is often already compromised.

Which IKO Models This Applies To

We work on the full IKO lineup you’re likely to find on San Antonio roofs: the Cambridge architectural series, Dynasty, Nordic, and the older Marathon lines that are still fighting the good fight across Alamo Heights and Terrell Hills. The underlayment compatibility question comes down to what was installed originally. IKO roofs installed before roughly 2015 often used 15-lb felt. Newer IKO systems are frequently paired with synthetic underlayments – IKO’s own StormShield, or a compatible synthetic like GAF FeltBuster or CertainTeed RoofRunner. When we repair a deck section, we match the underlayment class, not necessarily the brand, because mixing materials under IKO shingles matters more than the label on the roll.

Here’s a compatibility gotcha we see regularly in San Antonio: if your IKO roof is still under the manufacturer’s wind warranty, the repair has to use an underlayment that meets IKO’s current installation specs, or the warranty paperwork gets messy. Aftermarket synthetics almost always meet spec at a lower price than the OEM roll. We’ll tell you straight which is which when we quote it.

Mercer Roofing Co San Antonio is an independent service provider and not affiliated with IKO. We stock IKO-compatible materials, not IKO-branded underlayment, unless a warranty claim specifically requires it.

How to tell what you have: peel back a shingle tab at the eave line and look at the material under it. Felt looks like tar paper. Synthetic looks like woven plastic sheeting, often with a brand name printed on it. That takes ninety seconds and tells us most of what we need to know before we even climb up.

Signs Your IKO Underlayment & Deck Repair Is Failing

• Water staining on ceilings or attic rafters. This is the classic late-stage symptom. By the time water reaches the ceiling, it has already passed through the underlayment and soaked the deck. The stain tells us roughly where the breach is, but the rot spreads outward from there.
• Shingles that look wavy or buckled. IKO architectural shingles should lie flat. When the deck underneath swells from moisture, shingles ripple or lift. In San Antonio, where we swing from 100-degree days to overnight downpours, deck movement is common and it will not correct itself.
• Soft spots when walking the roof. If a section of roof feels spongy underfoot, the plywood underlayment is failing. This is a deck replacement, not a patch job. The soft area is always bigger than the visible damage.
• Granule loss concentrated in one area rather than evenly across the roof. Uniform granule loss means the shingle is simply aging. Concentrated loss in a patch usually means moisture is getting underneath and breaking down the shingle’s asphalt layer from below.
• Dark streaks or moss at the roof edges and in valleys. Water lingers in these areas longer, so when underlayment is compromised there, the deck stays wet. In San Antonio’s humidity, that constant damp invites organic growth that further holds water against the wood.

None of these symptoms reverse themselves. The underlayment is a wear item, and once the deck plywood is compromised, the fix is removal and replacement of that section – not a coating, not a caulk line, not a spray treatment.

Replacement Cost & What’s Included

For San Antonio homes, here’s what we quote most often:

The range is driven by how many sheets of decking have to come out, roof pitch, access (two-story on a San Antonio pier-and-beam adds setup time), and whether the repair sits in a valley or around flashings, which takes more cutting and sealing care. You get a written price before any work starts, every time. That number includes tear-out, new plywood, new underlayment seamed correctly, deck fastening, and haul-away. No change orders, no “we found more once we got in there” surprises – we quote what we see and honor it.

Every repair carries our 365-Day Done Right Promise: if it’s not right within a year, we make it right. That’s in writing, on every job. Grant Whitlock will tell you the same thing on the phone: a roof shouldn’t be something you worry about – that’s our job.

DIY or Call Us?

There’s a safe middle ground here. You can absolutely check your attic for water stains, feel for soft spots from below (do not walk a suspect roof), and peel back a shingle tab at the eave to identify your underlayment type. Those checks cost you nothing and help us quote more accurately.

The repair itself is not a weekend project, and it’s not just about skill – it’s about your safety. Working on a roof deck means working at height, on a surface that may already be compromised. A soft deck that gives way under your weight is a fall risk. Underlayment replacement also has to be seamed and flashed correctly or you’ve built the next leak into the roof on purpose. If the deck is soft, do not walk it at all. Let a trained crew with proper harnesses and fall protection handle the repair. Call (254) 276-4369 and we’ll schedule a deck assessment.

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