CertainTeed Underlayment & Deck Repair Nationwide

CertainTeed Underlayment & Deck Repair: The Los Angeles Owner’s Guide

We stock and install CertainTeed-compatible underlayment and replace rotted or failed roof decking across Los Angeles, with most deck repair jobs running $1,400 to $3,200 installed depending on how many sheets come out. We carry CertainTeed’s RoofRunner, DiamondDeck, and WinterGuard lines on the truck, so most underlayment replacements happen in a single visit. The way owners usually find us: a ceiling stain in the hallway, granules washing into the gutter, or a roofer from another company telling them the deck plywood is soft under the shingles and the whole system needs rework.

Call (213) 521-8272

Which CertainTeed Models This Applies To

If your home has CertainTeed shingles, the underlayment beneath them is almost always a CertainTeed product too, because CertainTeed’s warranty language rewards using their full roofing system. The three underlayment lines we install most in Los Angeles are RoofRunner (a synthetic felt replacement), DiamondDeck (a high-traction synthetic used under tile and steep-slope), and WinterGuard (a peel-and-stick ice and water barrier that matters most in canyon and hillside homes where wind-driven rain sneaks under the eaves). Here’s a compatibility gotcha we see regularly: DiamondDeck has a slip-resistant coating on one side, and if an installer lays it coating-side down, the shingles can’t key into the surface properly. We fix that mistake at least twice a month in Silver Lake and Mount Washington. As for OEM versus aftermarket, CertainTeed’s synthetic felt is quality stuff, and for Los Angeles UV and heat exposure we recommend staying with the OEM or a direct-equivalent synthetic rather than a big-box budget felt, which bakes brittle in five to seven years of Valley sun. The honest exception: if the decking itself is what failed, the plywood brand matters far less than the grade, and we use CDX exposure-1 plywood at minimum, often upgraded to OSB rated for roof sheathing on flatter decks.

Signs Your CertainTeed Underlayment & Deck Repair Is Failing

• Ceiling stains that grow after rain. Underlayment is your roof’s second line of defense. When a stain appears below a roof that’s only eight or ten years old, the underlayment has usually been compromised by heat-warped deck seams or old-style felt that finally cracked open.
• Wavy or sagging shingle lines visible from the curb. That’s not just an aesthetic issue. When decking gets soft, the shingle field loses its flat plane, and water starts pooling instead of shedding.
• Granules in the gutter that smell like asphalt. CertainTeed shingles hold their granules well, but when the deck flexes beneath them, the shingle mat cracks and the granule bond fails early. If you’re seeing heavy granule loss before year ten, the shingles are telling us the deck is moving.
• A musty smell in the attic after Santa Ana winds. Wind-driven dust and moisture both travel through a failed underlayment seam. In Pasadena and Eagle Rock, where Santa Anas hit hardest, we see underlayment that’s been sandblasted at the eaves and rakes long before the field fails.
• Soft spots you can feel when walking the roof. If a homeowner can feel the deck give underfoot, we treat that as an active leak risk, not a future one. By the time you can feel it, the plywood core is usually shot.

Replacement Cost & What’s Included

In Los Angeles, underlayment-only replacement on a typical 1,800-square-foot roof runs $900 to $1,700. When deck repair enters the picture, the total usually lands between $1,400 and $3,200, with the biggest variable being how many 4-by-8 sheets of plywood or OSB have to come out and whether we’re re-nailing the whole field or just the affected sections. Our price is written down before any work starts, every time. That written price includes material, labor, haul-away of old decking and felt, re-nailing where needed, and the underlayment itself. Every deck repair and underlayment replacement is covered by our 365-day written guarantee: if anything we touched fails within a year, we return and fix it at no cost. No fine print, no change orders halfway through the job.

DIY or Call Us?

There’s a safe middle ground here. You can check your attic for daylight coming through the deck seams, and you can look for the signs above from the ground or a ladder. What we don’t recommend is pulling shingles and underlayment yourself. Working on a roof in Los Angeles means working on slopes that run steeper than they look from the curb, and a torn-off underlayment section with exposed deck is a fall hazard and a leak hazard if the weather turns before you can re-cover it. If you want to know whether it’s a repair or a full re-roof, call us at (213) 521-8272. One of our technicians will inspect it and tell you straight whether you need a patch, a deck repair, or the full system, and you’ll get the price in writing before any work starts.

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