CertainTeed Underlayment & Deck Repair Nationwide

CertainTeed Underlayment & Deck Repair: The Jacksonville Owner’s Guide

We stock CertainTeed-compatible underlayment and repair roof decking throughout Jacksonville, and most underlayment repairs in this market run $1,400 to $2,900 installed depending on how many squares come off and what the deck looks like underneath. Deck repair, where we cut out rotted or water-damaged sheathing and replace it before new underlayment goes down, typically adds $4 to $6 per square foot of damaged deck. Most owners find out they need this work two ways: a leak shows up on the ceiling after a hard Jacksonville rain, or a roofer doing a shingle replacement pulls back the old felt and finds the deck has been getting wet for years without anyone knowing.

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Here’s what that looks like in practice. Water gets past a failed shingle or a dried-out flashing detail, soaks into the underlayment, and sits against the plywood deck. Florida heat and humidity keep that moisture active. The deck starts to swell, then delaminate, then rot. By the time you see a stain on the ceiling, the underlayment has already failed and the deck beneath it is usually compromised in at least a few spots. That’s the repair most CertainTeed owners in Jacksonville are actually dealing with, not just a new roll of felt.

Key takeaways:

• We install CertainTeed-compatible underlayment and repair decking, with written pricing before any work starts
• Installed underlayment replacement in Jacksonville runs roughly $1,400 to $2,900 for most homes
• Deck repair adds about $4 to $6 per square foot of damaged sheathing we cut out and replace
• We stock CertainTeed underlayment products on our trucks, along with compatible lines from GAF and Owens Corning
• Every job carries the 365-Day Done Right Promise in writing, with a free return visit if anything fails within the year

We’re an independent Jacksonville roofing contractor, not a CertainTeed dealer or affiliate. That means we can tell you plainly which CertainTeed product fits your roof and which aftermarket option does the same job for less, without a sales quota attached to one brand.

Which CertainTeed Models This Applies To

CertainTeed splits its roofing underlayment into three main lines, and they’re not interchangeable. The baseline is RoofRunner, a synthetic underlayment that comes in 10-square and 20-square rolls and is rated for standard shingle applications. The mid-tier is DiamondDeck, which is thicker, walkable, and includes a slip-resistant surface. The high-performance option is WinterGuard, a self-adhering ice and water shield that sticks directly to the deck and seals around fasteners. For Jacksonville, WinterGuard matters less for ice and more for our wind-driven rain and the low-slope sections of roofs in neighborhoods like San Marco or Ortega, where water sits longer than it should.

The compatibility gotcha is this: CertainTeed’s high-end shingle warranties often require specific underlayment to keep the warranty valid. If your roof has Landmark or Presidential Shake shingles, the fine print may name DiamondDeck or WinterGuard by product. It’s worth checking the original install documentation before someone slaps generic felt over it. If you don’t have the paperwork, we can identify what’s on your roof during a repair estimate.

For the deck itself, the repair material is standard: exterior-grade CDX plywood or OSB rated for roofing, matched to the existing thickness (typically 1/2-inch or 5/8-inch). CertainTeed does not manufacture decking, so the brand calculation is about the underlayment above the deck, not the deck board itself. We stock both plywood and OSB repair panels on the truck, along with RoofRunner, DiamondDeck, WinterGuard, and compatible underlayment from GAF and Owens Corning.

Signs Your CertainTeed Underlayment & Deck Repair Is Failing

• Water stains on ceilings or walls after rain. This is the classic tell. By the time water shows through drywall, it has already passed the shingles, saturated the underlayment, and likely damaged the deck. The question is never whether the underlayment failed, only how much deck came with it.
• Soft spots when walking the roof. A deck that flexes or feels spongy underfoot is rotted. Plywood delaminates, OSB swells and crumbles, and neither recovers. If a roofer can push a section down with one hand, it’s getting cut out and replaced.
• Visible dark staining or mold at the roof’s edge. Look up at the eave from a ladder. Dark streaks along the fascia or drip edge usually mean water has been running under the shingles and sitting against the deck edge. That’s underlayment failure, not a cosmetic issue.
• Shingles lifting or blowing off in specific patches. Shingles fasten through the underlayment into the deck. When the deck rots, the fasteners lose their grip. If you’re losing shingles after every summer thunderstorm, the deck beneath is usually the reason.
• Attic heat is worse than it used to be, or you smell mildew up there. A failed underlayment lets moisture into the roof assembly, and once moisture is in the Florida heat, mildew shows up quickly. This is the early warning most owners miss because they don’t go in the attic often.

If you’re seeing any two of these together, plan for deck repair as part of the underlayment job. We never quote underlayment replacement without pricing the deck work we can see, and we walk you through what’s visible versus what we’ll confirm once the shingles come off.

Replacement Cost & What’s Included

Here are the Jacksonville price ranges in dollars, based on what we’re currently seeing on jobs across the city.

• Underlayment replacement only (no deck repair): $1,400 to $2,900 installed, depending on roof size and which CertainTeed product goes down. That’s the full cost, including tear-off of the old underlayment, disposal, and labor.
• Deck repair (cut out and replace damaged sheathing): $4 to $6 per square foot of damaged deck, added on top of the underlayment price. Most homes need between 40 and 120 square feet replaced once the shingles come off, so expect $160 to $720 added.
• Full deck redeck (major rot or code-triggered replacement): $3.50 to $5 per square foot of roof area for all-new sheathing. This is a different scope of work than spot repairs and gets its own written quote.
• Underlayment on a full roof replacement: $0.60 to $1.10 per square foot depending on the product tier. This is relevant if we’re already replacing shingles and you want DiamondDeck or WinterGuard installed at the same time instead of RoofRunner.

What’s included in our number: labor, materials, delivery, removal and disposal of whatever we take off, and a written line-item price before any work starts. The price we put on paper is the price it stays. No change orders when the crew shows up with an excuse about “unforeseen conditions” and a new number. If we find more deck damage than the quote covered, we stop work, show you the problem, and give you a new written number before proceeding. That’s the Garrison Standard, and it’s the same on every job we run in Jacksonville.

Every underlayment and deck repair carries the 365-Day Done Right Promise in writing. If it’s not right, we make it right within one year, at no charge. No fine print, no argument.

DIY or Call Us?

The honest answer on underlayment replacement is this: a full underlayment swap means pulling every shingle off the section, and deck repair means cutting into a structural component of your roof. This is not a weekend project on a Jacksonville roof in August, and I’ve been doing this long enough to know where a homeowner without shingle experience starts losing material and the job both. Travis Oakley here. If you want to inspect before you call, grab a ladder and look at your roof’s edge for the dark staining mentioned above. That’s a safe check anyone can do. Getting onto a wet or steep roof to peel back underlayment is where the line is. Falls from residential roofs put more roofers in Florida hospitals than any other injury, and we’d rather you not join that statistic.

Here’s what we bring instead. Background-checked, uniformed technicians you can identify before they climb on your roof. The right CertainTeed product matched to what you have. And a written price before we pull the first shingle. If you’re unsure whether you need underlayment work at all, we’ll inspect and tell you straight, then put whatever does need doing in writing. Call (904) 719-6346 for a free estimate.

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