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CertainTeed Home Additions & ADU: The Los Angeles Owner’s Guide
A CertainTeed-specified home addition or ADU in Los Angeles typically runs $53,100 to $153,400 fully installed, and the right contractor should be able to walk your property, spec the CertainTeed product lines, and price the whole job in writing before you commit. Most homeowners discover they have a CertainTeed compatibility issue when a failed underlayment, roof flashing point, or siding transition detail starts showing water staining, or when an ADU they bought with plans specifying CertainTeed roofing and siding needs repair work and the original installer is gone. We see this regularly across LA: a detached ADU goes up, the CertainTeed roof membrane or exterior product was matched wrong to the structure, and now the homeowner needs someone who actually knows how CertainTeed systems tie together.
Which CertainTeed Models This Applies To
CertainTeed product lines that intersect with home additions and ADUs in Los Angeles focus on the exterior envelope: Landmark and Presidential roof shingles, WinterGuard waterproofing underlayment, CertaSeal ridge vents, MemBrain vapor barriers, and their siding profiles. The compatibility gotcha most owners miss is this: CertainTeed’s warranty system works as a complete integrated system, not individual products. If your ADU or addition calls for CertainTeed Landmark shingles but the underlayment underneath is a different brand or was installed over an unconditioned space without the right vapor strategy, the product itself isn’t “failing.” The install details were wrong. We have walked homes where the CertainTeed material was fine and the flashing transition at the new wall-to-roof intersection was the actual leak source.
How to identify what you have: look for the CertainTeed stamp on the shingle underside, check your original build paperwork for the specific product line (Landmark vs. Presidential matters for slope and exposure), and measure your roof pitch. For siding, CertainTeed’s Cedar Impressions and Board & Batten profiles have distinct shadow lines you can compare visually. When a part is truly failed and needs replacement, we spec OEM CertainTeed for anything still under warranty and recommend it even out of warranty when the rest of the system is CertainTeed. Mixing brands mid-system is how you void the remaining coverage. Sawyer Remodeling is an independent contractor and not affiliated with CertainTeed, but we install and repair their products regularly across Los Angeles.
Styles & brands we work with
Signs Your CertainTeed Home Additions & ADU Is Failing
- Water staining on the ceiling of your ADU near the wall line. This almost always traces back to a failed or improperly lapped underlayment at the roof-to-wall transition, not the shingle itself. CertainTeed’s WinterGuard needs to extend up the wall a minimum specified distance, and when it doesn’t, this is exactly where the leak shows.
- Shingle granule piles in your gutters or at downspout ends. Granule loss is normal at end-of-life, but on an ADU under 10 years old it signals poor ventilation. Los Angeles heat plus a sealed-up unconditioned attic space cooks shingles from the underside, and CertainTeed products age faster when the ridge vent or CertaSeal detail wasn’t installed by the books.
- Visible daylight in the addition’s attic space. If you can see light through the roof deck from inside, the Underlayment or decking has a genuine gap or rot point. That’s not a repair-when-convenient situation. That’s a water intrusion path actively working on your framing.
- Siding that feels soft or spongy near the bottom edge. CertainTeed polymer siding handles moisture well, but if the starter course was set too close to grade or the weep drainage behind the panel was blocked, water wicks up and breaks down the substrate. The panel itself may be fine; what’s failing is the drainage detail behind it.
- Peeling paint or bubbling at the junction of the addition and the original house. When a new structure ties into an older LA home, the flashing and expansion detail at that seam is the first thing to fail. The CertainTeed product you chose is likely not the problem; the transition was never detailed properly.
See the difference
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AfterReplacement Cost & What’s Included
For Los Angeles home additions and ADUs, the full installed range of $53,100 to $153,400 covers the structure itself with CertainTeed-specified roofing, siding, underlayment, and vapor management. A roof-only replacement on an existing ADU lands between $9,440 and $23,600. Siding replacement on a 400 to 600 square foot addition runs $4,130 to $12,980. What moves the number: the roof pitch and access, whether the existing sheathing is rotted, how much flashing detail exists at the wall-to-roof transitions, and whether we’re pulling a permit (in the city of Los Angeles, any structural or roofing change triggers LADBS review, and we pull permits on everything). Every estimate from us is a written line-item price before work starts. If the job scope doesn’t change, the number doesn’t change. And the 365-Day Done Right Promise applies after closeout: if something wasn’t done right, we make it right.
DIY or Call Us?
You can safely check your own roof penetrations, look for granule accumulation in gutters, and run a hose at the wall-to-roof transition while someone watches inside the ADU for water – that’s practical diagnostics. What you should not DIY is any work on the roof itself, any removal of siding that exposes the drainage plane, or any attempt to re-flash a roof-to-wall intersection. Los Angeles has specific code requirements for fire-rated construction in the hillside and urban-wildland interface zones, and CertainTeed products have manufacturer-mandated install details that affect warranty. We get a phone call at (254) 272-5876 at least once a month from someone who tried a roof repair themselves, got the underlayment lap backwards, and turned a $500 flashing fix into a $9,000 re-roof. Saving money on labor doesn’t mean much when you pay for it twice. If you want to know what you’re looking at before committing, call us and describe what you see. We’ll tell you honestly whether it’s urgent or can wait.
FAQs
A properly installed CertainTeed Landmark asphalt shingle roof lasts 22 to 28 years in Los Angeles, while the Presidential line can push past 30. The real variable is attic ventilation: LA’s heat, especially in the Valley and inland zones, shortens lifespan dramatically when the ridge vent or intake is undersized. If your ADU attic isn’t vented to CertainTeed’s spec, assume the lower end of that range. Call (254) 272-5876 and we can inspect your ventilation setup and give you an honest remaining-life estimate.
Yes, if the failure is localized: a single flashing point, one torn shingle, or a specific underlayment lap that opened up. Repairs in Los Angeles run $470 to $2,125. If you’re seeing failure in multiple spots or granule loss across the roof’s surface, patching is throwing money away. The honest answer depends on what we find. Call us for a free estimate and we’ll tell you which camp your roof falls into.
A targeted repair, such as re-flashing a wall transition or replacing a few shingles, takes half a day to a full day. A complete ADU re-roof runs 2 to 4 days depending on the roof size and whether the sheathing needs to be replaced. Siding replacement on an addition takes one to two days. We schedule work on specific days, not windows – you get a live arrival time and photo updates through The Relay Standard, so you’re never wondering where we are.
We keep common CertainTeed Landmark shingle bundles, WinterGuard rolls, ridge vent sections, and flashing materials on our trucks for repair calls. Specialty products like Presidential shingles or specific siding profiles may need to be ordered, which adds 3 to 5 business days. If your ADU or addition has an uncommon CertainTeed product we don’t carry, we’ll tell you the lead time before you owe us a dollar. Alongside CertainTeed, we also regularly install KraftMaid cabinetry, Cambria and Silestone countertops when projects call for them.
Written by Luca Romano, Owner, Sawyer Remodeling at Sawyer Remodeling, serving Los Angeles and nearby areas.
