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Tamko Underlayment & Deck Repair: The San Francisco Owner’s Guide
We stock and install Tamko-compatible underlayment and deck repair materials across San Francisco, with most underlayment repairs running between $450 and $1,400 installed depending on how much decking needs to come up. We keep Tamko TW Metal and Tile underlayment, composite deck boards, and replacement plywood sheathing on our trucks, so a lot of jobs get finished in one visit. Most San Francisco homeowners discover the problem the same way: a leak stain on the ceiling after a wet winter, or a soft spot underfoot when someone walks the roof during gutter cleaning. The underlayment did its silent job for years, and now it’s asking for attention.
If you have a Tamko roof and you’re seeing water where it shouldn’t be, this page covers what fails, what it costs to fix in San Francisco, and what a proper repair actually includes. Birchbark Roofing is an independent roofing contractor and not affiliated with Tamko, but we work with their underlayment and deck systems regularly and know how they behave in this climate.
Key Takeaways
- Most Tamko underlayment repairs in San Francisco fall between $450 and $1,400 installed, depending on deck damage beneath.
- Tamko TW Metal underlayment is a self-adhering membrane, while the Tile version is a polyester-reinforced sheet, and mixing them up is a common mistake.
- We carry OEM Tamko underlayment and quality equivalents, and we match the product to the slope and existing system rather than guessing.
- Deck repair means cutting out rotted sheathing and replacing it, not just patching over the top. Patching fails fast in San Francisco fog.
- Every Birchbark job includes a written price before work starts and a 365-Day Done Right Promise.
Which Tamko Models This Applies To
Tamko makes two underlayments that show up on most San Francisco roofs: TW Metal and TW Tile. TW Metal is a self-adhering, rubberized asphalt membrane meant for metal roofing and areas that catch a lot of water, like valleys and eaves. TW Tile is a polyester-reinforced mechanically attached sheet designed under tile and shake. They are not interchangeable. TW Metal comes in 36-inch by 66-foot rolls with a split release liner, and TW Tile comes in 48-inch by 250-foot rolls that need cap nails or staples on a specific schedule. If a previous installer used TW Tile where the slope called for a self-adhered membrane, that is usually the first thing that fails.
For deck repair, the compatibility question is simpler: the sheathing under a Tamko roof is standard plywood or OSB, and what matters is thickness. Most San Francisco homes built before 1980 used 1×6 or 1×8 board sheathing, especially the older Victorians in the Mission and Noe Valley. Newer construction typically has 15/32-inch or 19/32-inch plywood. You do not want a repair crew nailing a 19/32-inch patch into a roof framed for 15/32-inch sheathing without shimming, because the patch will sit proud and telegraph through the underlayment. We measure before we quote, and the written estimate reflects the actual deck condition we find, not a guess from the ground.
OEM versus aftermarket matters less for Tamko decking than for underlayment. The deck boards themselves are standard lumber, and we use CDX plywood rated for roof sheathing. For underlayment, we prefer OEM Tamko when the warranty on the roof system is still active. If the warranty is expired, a quality self-adhered membrane from a brand like GAF or CertainTeed meets or exceeds the same ASTM standards at a similar price. Either way, you will see the exact product named on your written estimate before we start.
Styles & brands we work with
Signs Your Tamko Underlayment & Deck Repair Is Failing
- Water stains on ceilings or walls after rain – This is the most common signal in San Francisco, where wind-driven rain pushes water sideways. Underlayment that has aged out or was installed wrong lets moisture through at seams and nail penetrations, and the stain is the first visible proof.
- Soft or springy roof deck when walked on – If a roofer weighs 180 pounds and the plywood flexes more than a quarter inch, the decking has lost structural strength. In San Francisco’s damp microclimates, like the Sunset and Richmond districts, we regularly find sheathing rotted from years of slow leak exposure that never showed up inside the house.
- Curling or lifting underlayment at roof edges and valleys – Self-adhered membranes like Tamko TW Metal can lose their bond over time, especially where the roof gets blasted by salt air and UV. Once the edge curls, water walks right underneath.
- Mold or mildew smell in the attic – Underlayment failure lets moisture into the attic space, and San Francisco’s foggy summers keep that moisture around long enough for mold to start. The smell is often strongest in the morning before the sun burns it off.
- Gaps between shingles or tiles that seem wider than they were** – When the deck beneath is moving or rotting, fasteners loosen and the roofing material above shifts. The visible gap is a symptom of deck movement, not the cause.
None of these signs fix themselves, and in San Francisco’s climate, delay usually means more deck replacement than the original repair would have required.
See the difference
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After
Before
After
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AfterReplacement Cost & What’s Included
For a Tamko underlayment repair on a typical San Francisco home, you are looking at $450 to $900 when the decking underneath is sound. If the deck is compromised, which is common in older Richmond and Sunset district houses where the original sheathing is over 60 years old, the job runs $700 to $1,400 installed. The spread depends on how many sheets of plywood or linear feet of board sheathing need replacement, whether the roof has multiple layers to strip, and how steep the slope is.
| Scope | Typical Price in San Francisco |
|---|---|
| Underlayment repair only, flat or low slope | $450 – $700 |
| Underlayment repair with 1-2 sheets of deck replacement | $600 – $900 |
| Underlayment plus extensive deck replacement (3+ sheets) | $900 – $1,400 |
| Underlayment replacement for the full roof | $3,000 – $8,000 depending on roof size and layers |
Every Birchbark estimate includes labor, materials, debris hauling, and a written breakdown of the line items. No change orders. No “we found extra damage” surprises. Erik Lindgren walks every slope and writes down exactly what he finds before a number ever reaches you. That is how we have always run estimates, because a price without a job site inspection is just a guess wearing a nice shirt.
DIY or Call Us?
You can safely check a few things from the ground or a ladder: look for curling underlayment at the eaves, check for soft spots by pressing a broom handle into the deck (gently, without walking a roof you do not know), and note where interior stains line up with roof penetrations. What you should not do is pull up roofing material and attempt a deck repair yourself. Roof sheathing is structural, a fall from even a single-story San Francisco roof is a life-changing injury, and cutting deck boards without properly supporting the rafters beneath is how people end up in emergency rooms. Add the fact that most San Francisco homes have two or more layers of old roofing, and a DIY repair turns into a bigger mess very quickly.
If the roof is walkable and you just want to know what you are dealing with before you spend money, call us at (831) 228-3330. We will send someone out, assess the deck and underlayment, and give you a written price before a single shingle moves. That is just how the job starts.
FAQs
Tamko underlayment typically lasts 15 to 25 years in San Francisco, with the shorter end of that range applying to foggy western neighborhoods like the Sunset and Richmond where persistent moisture ages materials faster. The deck underneath should last 40-plus years if the roof stays watertight. Call (831) 228-3330 for an inspection if your roof is over 20 years old.
Small areas of failing underlayment can be repaired by removing the roofing material above, splicing in new underlayment with proper overlap, and reinstalling the roofing. If the damage covers a large area or the deck below is soft, a full section replacement is the honest fix. We will tell you which one applies after a roof inspection, and you will see it in writing before any work begins.
Most underlayment and deck repairs in San Francisco take one to two days, depending on how much decking needs replacement and how many layers of old roofing have to come off first. We protect the inside of your home with shoe covers and drop cloths on every visit, and we photograph the completed clean-up before the crew leaves.
Yes, we stock Tamko TW Metal and TW Tile underlayment, plus CDX plywood for deck replacement, on our trucks for most San Francisco service calls. If your roof requires a specific Tamko product we do not have on board, we source it the same day and finish the job as scheduled.
If you are dealing with a Tamko underlayment or deck problem in San Francisco, call Birchbark Roofing at (831) 228-3330 for a free estimate. A live person answers, we send a uniformed, background-checked technician to your home, and you get a written price before anything gets touched.
Written by Erik Lindgren, Owner, Birchbark Roofing San Francisco at Birchbark Roofing San Francisco, serving San Francisco and nearby areas.