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CertainTeed Underlayment & Deck Repair: The San Francisco Owner’s Guide
If your CertainTeed underlayment has torn, wrinkled, or started letting water through, or if the plywood decking beneath it has rotted or delaminated, we stock and install CertainTeed-compatible underlayment and deck repair materials across San Francisco, with most jobs completed in one to two days. Installed pricing for underlayment replacement and deck repair in San Francisco typically runs $4.50 to $9.00 per square foot depending on deck damage, roof pitch, and whether we’re matching DiamondDeck, RoofRunner, or WinterGuard underlayment. Most owners discover the failure the same way: a ceiling stain after the first real rain of the season, granules collecting in a gutter, or a roofer’s inspection photo showing plywood that’s gone soft under a seam. Travis Oakley and our crew have pulled back enough CertainTeed underlayment in this city to know exactly what fails first, and it’s rarely the membrane itself, it’s usually the deck and the seam details around it.
Which CertainTeed Models This Applies To
CertainTeed’s underlayment line splits into three families, and the repair path depends on which one is on your roof. RoofRunner is the synthetic entry point, a polypropylene sheet that goes down fast but isn’t rated for long-term exposure. DiamondDeck is the high-performance synthetic with better tear resistance and slip grip, and it’s what we most often install on San Francisco re-roofs. WinterGuard is the self-adhered ice-and-water barrier CertainTeed specifies for eaves, valleys, and penetrations, and in San Francisco’s fog-soaked microclimates we see it spec’d more aggressively than the manufacturer minimums. The compatibility gotcha most owners hit: CertainTeed warranties require underlayment to be installed over decking that meets specific dryness and fastener standards, and if the deck has rotted, the underlayment warranty is void no matter how good the membrane was. That means deck repair isn’t an add-on, it’s the prerequisite. For decking, we match CertainTeed’s own recommendations: 1/2-inch or 5/8-inch CDX plywood or OSB rated for the rafter spacing, with H-clips at panel edges per San Francisco code. We’re an independent contractor, not a CertainTeed affiliate, which means we match the spec honestly without pushing a brand line.
Styles & brands we work with
Signs Your CertainTeed Underlayment & Deck Repair Is Failing
- Ceiling stains or drips in interior corners and around skylights. Water is getting past the underlayment at a seam or penetration, and the deck below is already wet. By the time paint bubbles, the plywood has usually been absorbing moisture for weeks.
- Wrinkled or lifted underlayment visible at the eaves or rakes. Synthetic underlayment that wasn’t fastened to the manufacturer’s pattern can flutter and tear in San Francisco’s winter wind, exposing the deck underneath. DiamondDeck and RoofRunner both have specific fastener schedules, and skipping them is the most common install failure we correct.
- Granules in the gutter or downspout. CertainTeed shingles shed granules as they age, but a sudden heavy load usually means the shingle above the underlayment has worn through, and the membrane is now doing the waterproofing job alone. That it’s holding is good. That it’s now the only barrier is not.
- Soft spots or visible sag in the roof plane. This is deck failure, not underlayment failure. Rotted plywood delaminates and dips between rafters, and no membrane, CertainTeed’s included, can bridge a deck that’s lost its structural grip.
- Mold or musty smell in the attic after heavy fog or rain. San Francisco’s fog cycle means decks that get wet once may never fully dry. Trapped moisture under a still-intact underlayment rots the plywood from below, and the smell is your first warning that the deck needs to be opened and inspected.
Replacement Cost & What’s Included
For San Francisco homeowners, here’s the range we quote on paper, before any work starts. Underlayment-only replacement over sound decking runs $4.50 to $6.50 per square foot installed, including tear-off of the old membrane, new CertainTeed-compatible underlayment, fasteners, and full clean-up. When deck repair enters the picture, which it does on roughly 40% of the CertainTeed roofs we open in this city, the combined job runs $6.50 to $9.00 per square foot, covering the rotted panel replacement, new underlayment, and the necessary H-clips and fasteners. What drives the range: roof pitch (steeper Victorians near Alamo Square cost more than low-slope Sunset District flats), how many panels of decking need to come out, and whether we’re peeling back one layer or two. Parts and labor are never separated into vague bundles, you’ll see them as line items. Every underlayment and deck repair we do is backed by our 365-Day Done Right Promise: in writing, for one full year, with a free return visit if anything fails.
See the difference
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AfterDIY or Call Us?
Here’s the honest split. An owner can safely do one thing: look in the attic on a dry day and check for water staining on the underside of the deck, especially around penetrations and at the eaves. That tells you if water has already gotten through. But pulling back underlayment means standing on a roof, and on San Francisco’s steep pitches and fog-slick surfaces, that’s a fall risk no homeowner should take on a weekend. The other problem is the repair itself: underlayment only works if the deck below is dry, fastened to spec, and sound, and assessing that correctly takes a trained eye and a moisture meter, not a hammer. If the deck’s rotted, patching the membrane on top just hides the problem for another season. If you’re seeing any of the signs above, call (831) 318-8819 and we’ll do a full inspection with the deck opened and measured properly.
FAQs
CertainTeed’s synthetic underlayments like DiamondDeck and RoofRunner are rated for 30-plus years when kept dry and installed to spec, but in San Francisco the real lifespan depends on the deck and the seams. Fog condensation, long wet seasons, and wind-driven rain at the eaves all shorten the practical life, and we typically see underlayment failing in 15 to 20 years here, almost always at seams, valleys, and penetrations before any field failure. Call (831) 318-8819 and we’ll tell you honestly what’s left in yours.
Small tears around a single penetration can sometimes be patched with a self-adhered CertainTeed-compatible membrane, but if the tear is in a seam, valley, or extends more than a few feet, the right fix is to replace the affected sections entirely. Underlayment is a system, not a patchwork, and water will find every seam you leave behind. We’ll tell you where repair pencils and where replacement is the only honest answer.
Most San Francisco jobs take one to two days depending on how much decking needs to be pulled, whether the shingles above can be saved or need to come off, and the roof pitch. We stage materials the day before, show up in uniform, and leave the site clean the same day we finish. You’ll get a written timeline with your written price.
Yes. Our trucks carry DiamondDeck and RoofRunner synthetic underlayment, WinterGuard self-adhered membrane, coated fasteners, H-clips, and both 1/2-inch and 5/8-inch CDX deck panels. We also stock compatible materials from GAF and Owens Corning, so if your roof has a mixed-brand history, we can match what’s already up there instead of forcing a brand change.
Call for a Free Estimate
If you suspect underlayment or deck failure, call Brennan Roofing Co San Francisco at (831) 318-8819. Travis Oakley or one of our crew will schedule a free inspection, put the price in writing before any work starts, and stand behind the repair for a full year. A good roof shouldn’t need to be talked about, it should just hold.
Written by Travis Oakley, Owner, Brennan Roofing Co at Brennan Roofing Co San Francisco, serving San Francisco and nearby areas.