CertainTeed Underlayment & Deck Repair Nationwide

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

We stock and install CertainTeed-compatible underlayment and deck repair materials across San Antonio, with most deck repairs running between $350 and $1,400 installed depending on the damaged area’s size and whether we’re replacing rotted decking, failed underlayment, or both. We typically complete deck and underlayment repairs the same day we start, and we carry CertainTeed RoofRunner, DiamondDeck, and WinterGuard materials on our trucks. Most San Antonio homeowners discover the problem after a leak shows up on the ceiling, or when they climb into the attic and spot water staining on the underside of the roof deck. By the time you see the stain, the underlayment has usually been breached for weeks.

Call (254) 276-4369

Which CertainTeed Models This Applies To

CertainTeed makes several underlayment products, and they are not interchangeable. RoofRunner is their synthetic underlayment, sold in 250-foot rolls, and it’s what we install under most CertainTeed shingle systems in San Antonio, including Landmark, NorthGate, and Grand Manor lines. DiamondDeck is the peel-and-stick ice and water shield, and WinterGuard is the higher-temperature version rated for metal roofs and areas where the deck gets hotter than 140 degrees. If your roofer used felt paper instead of a synthetic underlayment, that is not a CertainTeed product at all, and it fails much faster in San Antonio’s heat cycle. The compatibility gotcha we see constantly: CertainTeed’s warranty language expects their underlayment to be fastened with plastic cap nails or staples, and a lot of San Antonio roofs have plain roofing nails driven through the material, which compromises the water barrier at every penetration point. If you still have the roll label, check the product name and the ASTM number printed on it. If not, a quick attic look tells us what type is up there.

Signs Your CertainTeed Underlayment & Deck Repair Is Failing

• Water stains on ceilings or walls after a San Antonio downpour. This usually means the underlayment has torn or the decking has rotted enough that water is getting past the shingles and sitting on the wood. Stains don’t appear until water has been moving through the deck for a while.
• Soft or spongy spots on the roof deck. Walkable only from inside the attic, but if you can press a screwdriver handle into the decking and it gives, the plywood or OSB is rotted. Deck rot in San Antonio is almost always from long-term underlayment failure, not a single storm.
• Shingles lifting or buckling along a ridge or valley. When the deck moves or swells, shingles follow. Buckling in a valley is often the first visible sign that decking underneath has swollen from trapped moisture.
• Granules accumulating in gutters faster than normal. Shingles wear faster when the deck beneath them flexes. If you’re cleaning grit out of your gutters every month, the deck under those shingles is telling you something.
• Damp or musty smell in the attic after rain. Underlayment that has reached the end of its life lets moisture through even when the shingles look fine from the ground. A musty attic in a dry climate like San Antonio means water is getting in.

Replacement Cost & What’s Included

For underlayment replacement and deck repair in San Antonio, homeowners should expect to pay between $350 and $1,400 for a typical rotted-deck section with new CertainTeed underlayment installed. A small repair involving one sheet of decking and a few feet of underlayment starts around $350. Larger sections, ridge line damage, or work requiring rafter repair push cost toward the upper end. Steep pitches and two-story homes add labor. Every price we quote at Mercer Roofing is written, line by line, before any work starts, so you know the exact cost of materials, labor, and disposal. The workmanship is covered by our 365-Day Done Right Promise: if the repair isn’t right within a year, we make it right at no charge, and a free second visit is included if the repair fails.

DIY or Call Us?

You can safely check your attic for water stains and press on the decking from below to find soft spots. That’s about where DIY should stop. Removing shingles, cutting out rotted decking, and installing new underlayment means working on a roof surface, often on a pitch, and doing it wrong leaves your home exposed to the next San Antonio storm. A bad underlayment seam or a poorly fastened deck patch will leak, and by the time you see the damage, the repair costs more than calling us would have in the first place. We’ve also seen homeowners pull shingles and discover the deck condition is much worse than expected, with no way to safely button the roof back up for the night. If you want to know exactly what’s going on up there, call (254) 276-4369 and we’ll send a technician to inspect it. The estimate is free.

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