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Tamko Home Additions & ADU: The Los Angeles Owner’s Guide
A Tamko home addition or ADU project in Los Angeles typically runs $53,100 to $153,400 installed, depending on square footage, foundation work, and whether you’re building a detached unit or an attached bump-out. Most LA homeowners reach out to us after a smaller remodel has exposed a structural problem, or when an existing addition starts showing water intrusion at the roofline where the new framing ties into the original house. A failing addition rarely announces itself with a bang. It’s a slow leak, a hairline crack in the stucco, a door that suddenly sticks.
That’s the moment to get eyes on it. We stock common Tamko-compatible building materials on our trucks and can typically assess the condition of your addition or ADU within a few days of your call. Sawyer Remodeling is an independent contractor and not affiliated with Tamko, but we work with their product lines because they hold up in California’s dry-heat-and-rain cycling better than most budget materials we’ve pulled out of walls over the years.
Key Takeaways
- Installed cost range in Los Angeles: $53,100 – $153,400 for a full home addition; ADU construction runs $106,200 – $259,600.
- Biggest failure points: roof tie-ins, flashing at the addition wall line, and stucco cracking from improper curing in dry heat.
- Lifespan reality in LA: a properly flashed addition should go 30 – 50 years; a badly flashed one will show damage in 3 – 5.
- Sawyer Remodeling: independent, not a Tamko dealer, but we install and repair additions built with Tamko materials every season.
Which Tamko Models This Applies To
Tamko doesn’t make “home additions” as a single product. What you’re likely dealing with is a remodel or addition built using Tamko roofing, waterproofing, or flashing components, or an ADU structure where Tamko underlayment and moisture-barrier products were specified by the original contractor. The part that matters most in LA isn’t a model number, it’s the flashing system where new framing meets old stucco or shingles.
Here’s the compatibility gotcha we see regularly: Tamko’s self-adhered flashing and underlayment products come in a narrow temperature window for proper adhesion. In Los Angeles, that means an installation done in August behaves differently than one done in January. If the original installer didn’t account for surface temperature at the roof-wall junction, the membrane can peel back within a few years even though the product itself is sound. That’s not a Tamko defect. That’s an installation-temperature issue we fix by removing the failed section, cleaning the substrate, and re-flashing with a primer-matched membrane at the correct temperature range.
What we look for when you call about a failing addition: the original building plans or permit packet (which list material specs), the condition of any visible flashing at rooflines and window heads, and the age of the structure. A 2010 addition in Silver Lake will have different flashing details than a 2022 ADU in Woodland Hills. Both matter.
Styles & brands we work with
Signs Your Tamko Home Addition & ADU Is Failing
- Water staining at the ceiling line where the addition meets the original house. This almost always points to failed flashing at the transition point. The original roofline was cut into, and if the tie-in wasn’t layered correctly, water tracks sideways before it shows up as a stain.
- Hairline stucco cracks running diagonally from window corners. In LA’s dry summers, stucco cures fast. Without proper control joints at addition-to-house intersections, the new wall moves independently of the old structure and cracks the skin.
- Doors or windows that stick in the addition but not in the main house. Framing has settled. This happens when the addition’s foundation wasn’t tied to the original with proper rebar doweling, and the two structures drift at different rates.
- Peeling paint or soft drywall near the baseboards of an exterior wall. This is a moisture-barrier failure, often where Tamko or similar underlayment was terminated too high or not lapped correctly at grade. Water wicks up behind the wall and shows itself at floor level first.
- A musty smell that comes and goes with rain. Intermittent smell means water is getting in and drying out between storms. You won’t always see the stain. The smell is the signal.
See the difference
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AfterReplacement Cost & What’s Included
In Los Angeles, a full home addition runs $53,100 to $153,400. An ADU, which is a separate living unit with its own kitchen and bath, runs higher at $106,200 to $259,600 because of utility runs, foundation work, and separate meter requirements. A garage conversion sits between them at $35,400 to $94,400.
If you’re not building from scratch but repairing a failing section, the math changes. A flashing repair at the roofline junction typically falls in the $700 – $3,000 range depending on access and how much of the surrounding roofing has to come up. Stucco crack repair with proper expansion-joint installation runs $500 – $2,500 per wall section. Those are the kind of numbers you should get in writing before work begins, and that’s exactly what we provide under The Relay Visibility Guarantee: a written price before any tool is picked up, live arrival tracking, and before-and-after photo updates. Our 365-Day Done Right Promise says if it’s not right, we make it right, in writing.
DIY or Call Us?
Here’s the honest split. You can safely inspect the visible parts of your addition without us: look at the flashing where the roofline meets the wall, check for cracked caulk at window heads, walk the perimeter and eyeball the stucco for diagonal cracks. Write down what you see. Take photos. That’s genuinely useful when you call.
What I’d caution against is pulling up roofing or cutting into stucco yourself. The tie-in point between an addition and the original structure carries roof load and water load simultaneously. Get the layering wrong and you’ll double the repair cost. If the project involves roof access on anything higher than a single story, leave it to a pro. Luca Romano has been working Los Angeles rooflines for over two decades, and the most expensive repairs we’ve done at Sawyer Remodeling are the ones that started as a weekend DIY attempt. Good work doesn’t need a sales pitch, it just needs to be done right. Call (254) 272-5876 and we’ll walk the property with you.
FAQs
A properly built addition in LA should last 30 to 50 years before major structural intervention, assuming the flashing and foundation work were done correctly at the original build.
Yes. Most failure points, flashing at the roofline, stucco cracks from settling, and moisture-barrier gaps at grade, are repairable without tearing down the structure. The repair cost depends on how long water has been running unchecked. Call (254) 272-5876 for a free inspection and written estimate.
Most flashing and stucco junction repairs take 2 to 4 working days in Los Angeles, assuming weather cooperates and no hidden structural damage surfaces once we open the wall.
We stock common Tamko-compatible underlayment and flashing materials on our trucks, and we can match most existing product lines or specify an approved equivalent for your project. We also work with materials from KraftMaid, Cambria, and Silestone for interior finishes.
Sawyer Remodeling is part of the Relay Home Co. family of independent local businesses. We answer our phones with a live person around the clock, and every job gets a written price before work starts. If your LA addition is showing its age, call (254) 272-5876 and we’ll schedule a walkthrough. The estimate is free, and the number we write down is the number you’d pay.
Written by Luca Romano, Owner, Sawyer Remodeling at Sawyer Remodeling, serving Los Angeles and nearby areas.
