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Tamko Home Additions & ADU: The San Jose Owner’s Guide
If you’re planning a home addition or ADU in San Jose and you’re researching Tamko building products, you’re likely trying to figure out whether the materials already on your house (or specified for your new build) will hold up, what they’ll cost to install, and who can actually do the work. At Penhallow Remodeling San Jose, we install and build additions and ADUs that incorporate Tamko roofing, waterproofing, and decking products, with full home additions typically running $53,100 – $153,400 and ADU construction ranging from $106,200 – $259,600 depending on square footage, foundation work, and finish level. Most owners discover a Tamko-related failure the hard way: a roof leak that appears after the first heavy winter rain, a deck board that cracks under a patio chair, or flashing that pulls away from a new bump-out wall. Sometimes it’s not a failure at all; it’s the moment you realize your original contractor never actually installed the Tamko underlayment you paid for.
Which Tamko Models This Applies To
Tamko makes a broad line of residential building materials, but for San Jose additions and ADUs, you’re almost always dealing with one of three product families: Heritage or Elite asphalt shingles, TW-60 or TW-40 underlayment, and EverGrain composite decking. The compatibility gotcha most homeowners run into is mismatch: the Heritage line has a different exposure profile than Elite, and if your addition’s roofline doesn’t match the existing slope (common in San Jose ranch homes where a bump-out has a lower pitch than the original roof), you need the right underlayment spec, not just the right shingle. We identify the product by looking at the original packaging or the printed code on the underside of a shingle or deck board. For underlayment, the print pattern on the membrane tells us which TW series you have. When it comes to OEM versus aftermarket: Tamko’s proprietary products don’t have many true aftermarket equivalents, and where a generic substitute exists (like generic peel-and-stick underlayment), we’ve found the OEM version holds up better in California’s UV-heavy dry season followed by sudden winter downpours. We won’t talk you into a substitution unless we’ve seen it perform over at least five San Jose seasons.
Styles & brands we work with
Signs Your Tamko Home Additions & ADU Is Failing
- Granule loss on shingles near the addition’s roofline. If you see a streak of grey or black pebbles in your gutter every time it rains, the shingle surface is breaking down. Granule loss accelerates fast once the underlying asphalt is exposed to San Jose’s summer sun, and it’s a sign the shingle has maybe two seasons left before it cracks.
- Dark stains or soft spots on the ceiling where the addition meets the original house. This almost always means the transition flashing, the metal piece that connects old roof to new roof, wasn’t lapped correctly. Water wicks underneath during the first real storm, and the stain appears weeks later, usually in the corner of the room where the bump-out wall meets the existing exterior wall.
- Underlayment peeling or bubbling visible at the eaves. Walk outside and look up at the roof edge just after a rain. If you see the underlayment lifting away from the fascia board or blistering in the top coat, it’s failing. This happens when a contractor used a non-Tamko underlayment that doesn’t bond to Tamko shingles the way the matched system does.
- Deck boards (EverGrain) flexing more than they did last year. Tamko’s composite decking needs joist spacing of 16 inches on center or less. If the original framing was spaced wider, the boards get bouncy, then they crack at the fastener line. That bounce is your warning that a board is about to split.
- Musty smell inside the ADU after it’s been closed up for a week. Not always visible, but always telling. It means moisture is getting past the wall or roof barrier, which for a Tamko system usually points to tape or flashing that failed at a penetration: a vent, a dryer box, or the mini-split line set. The problem is water, but the source is a gap.
Replacement Cost & What’s Included
If this is a Tamko-related repair on an existing addition or ADU, rather than a full new build, the cost is far smaller than the full project ranges above. Replacing a section of Tamko shingles and the underlying flashing at a transition line in San Jose typically runs $470 – $2,125 depending on how much decking underneath has rotted. Replacing failed underlayment on a small ADU roof (400 – 600 square feet) lands around $2,300 – $4,700 with tear-off and disposal. Full re-roof of a 750-square-foot ADU with Tamko Heritage shingles: $9,440 – $23,600. What drives the range is access (a second-story addition on a steep pitch costs more in labor and safety equipment), how much decking has to be replaced, and whether the original contractor left us a surprise under the old shingles. We’ve opened roofs in Willow Glen and found the previous crew had skipped the underlayment entirely. Every one of our numbers is written, line by line, with parts and labor separated, and we hand it to you before we touch anything. The work carries our 365-Day Done Right Promise: if something fails inside a year, we come back and fix it at no charge, in writing.
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AfterDIY or Call Us?
For Tamko shingles and underlayment, there’s a line. You can safely do a visual check: walk the perimeter, look at the roof edge, check the gutter for excessive granules, and look at the corners of ceilings inside the addition for stains. That’s your job if you want to catch a problem early. But do not get on a ladder and attempt to peel back shingles, pull up failed flashing, or re-adhere underlayment on a second-story roof. That work means working at height on a surface that’s already compromised, and the fall risk is real. We’ve also seen homeowners use roofing cement from a hardware store to “fix” a transition leak, which seals the water in and turns a $500 flashing repair into a $4,000 sheathing replacement. If you see signs of failure, call (669) 274-2362 and we’ll put a background-checked technician on your roof. The inspection is free.
FAQs
Tamko Heritage shingles typically last 20 to 25 years on a San Jose addition, but that depends on attic ventilation and whether the roof gets afternoon sun on the west side. Poorly ventilated additions where heat builds up in the attic can shorten that to 12 to 15 years. Call (669) 274-2362 and we’ll inspect your roof and tell you honestly what’s left in it.
Yes, in small sections, if the problem is limited to one area and the rest of the membrane is still bonded. But if the peeling is widespread, patching is throwing money away. We’ll give you a straight answer either way, with photos. Call (669) 274-2362 to schedule a free inspection.
A flashing repair or small shingle replacement takes one day, a full ADU re-roof takes two to three days, and a full addition roof with tear-off usually runs three to five days depending on weather and size. You’ll get a fixed arrival window before we start, not a “sometime next week.” Call (669) 274-2362 for a written estimate with a date on it.
We keep the most common Tamko shingle colors, underlayment, and flashing on hand for San Jose jobs, and anything we don’t have on the truck we can typically get from our local supplier within two business days. We also work with KraftMaid cabinetry, Cambria and Silestone countertops when the addition includes a kitchen or bath. Call (669) 274-2362 and a real person will answer, tell you what’s in stock, and get you on the schedule.
Get a Written Tamko Repair or Addition Estimate in San Jose
If you’ve got a failing Tamko roof on your addition, a leak in your ADU, or you’re planning a new build and want the materials done right the first time, we’ll give you a written number before any work starts. No verbal ballpark that changes at the door. No crew showing up without a fixed scope. You’ll get the real price, the real timeline, and a guarantee in writing. Trevor Nash built this company on the idea that a homeowner who understands the job is a homeowner who stays calm. Give me the real problem and I’ll give you the real number. Call Penhallow Remodeling San Jose at (669) 274-2362 for a free estimate.
Written by Trevor Nash, Owner, Penhallow Remodeling San Jose at Penhallow Remodeling San Jose, serving San Jose and nearby areas.
