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CertainTeed Home Additions & ADU: The Los Angeles Owner’s Guide
If you’re planning a home addition or ADU in Los Angeles and want CertainTeed materials specified into the build, we can help you scope it, price it, and get it permitted. A full home addition in Los Angeles typically runs $53,100 – $153,400, while a detached ADU generally lands between $106,200 and $259,600 depending on size, foundation work, and finish level. Most owners reach out when their existing addition is showing framing, siding, or drywall failures, or when they’ve been told their CertainTeed-specified plans won’t pass inspection without corrections. We walk the site, identify what’s actually failing, and give you a written number before any work starts.
Which CertainTeed Models This Applies To
CertainTeed doesn’t manufacture “home additions” as a single product, but their material lines show up throughout additions and ADUs across Los Angeles: CertainTeed drywall, insulation, WeatherBoards fiber cement siding, and their roofing shingles are the usual suspects. What matters for compatibility is which product line you have. If your addition is sided with WeatherBoards, the 7/16″ lap profile takes different flashing and trim than the vertical panel line. If the drywall inside is CertainTeed’s M2Tech or SilentFX, the fire-rating and sound specs matter when you’re tying into an existing wall assembly. The practical step is to find the product label on an exposed edge or in your original permit documents; if you can’t locate it, we can identify what’s installed during the estimate. One gotcha we see often in Los Angeles: additions built before 2010 used CertainTeed materials that are now discontinued, which means an “identical” match often requires a modern equivalent with slightly different thickness or profile. We’ll tell you before we quote whether a true match exists or whether you’re looking at a close-equivalent substitution.
Styles & brands we work with
Signs Your CertainTeed Home Additions & ADU Is Failing
- Visible siding swelling or buckling near the bottom course. In Los Angeles, sprinkler overspray and soil moisture wick into fiber cement if the clearance to grade is under 6 inches. Once the lower boards swell, water moves behind them and into the framing.
- Drywall cracks running diagonally from window and door corners. This usually means the addition settled or the header was undersized for the span. In older ADUs around neighborhoods like Leimert Park and Mid-City, we see this where a garage was converted without upgrading the original header.
- Musty smell or darkened insulation in the attic knee walls. CertainTeed fiberglass batts lose R-value when they get damp, and the vapor barrier detail on California additions often gets installed backward. The symptom is a room that won’t hold temperature and a smell that won’t go away.
- Roof shingle granule loss concentrated where the addition ties into the main house. That transition valley is where most water intrusion starts. CertainTeed shingles carry a solid warranty, but the flashing detail where two roof planes meet is only as good as the installer who did it.
- Interior walls that feel damp or paint that bubbles along the ceiling. This often traces to the addition’s roof venting. If the original builder skipped proper intake vents, the CertainTeed decking under those shingles is steaming and delaminating, and you’ll see it at the ceiling first.
See the difference
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AfterReplacement Cost & What’s Included
For a failing addition or ADU in Los Angeles, the scope determines where you land in that $53,100 – $153,400 range. A siding replacement on a small ADU with framing repair might run $8,000 – $20,000. Full interior remediation with drywall replacement, insulation, and refinishing on a larger addition can run $40,000 – $80,000. A complete tear-down and rebuild of a poorly done addition lands at the top of the range. What drives the number: the amount of framing that’s rotted or undersized, whether electrical and plumbing need to be brought to current code, and how much of the CertainTeed material can be salvaged versus replaced. Every quote includes labor, materials, debris hauling, and permits. You get the written price before we start, and the number on day one is the number on the final invoice. No change orders for work we scoped correctly.
DIY or Call Us?
You can safely check a few things yourself: look for visible siding damage at the base of the walls, check that gutters are clear and downspouts route water at least three feet from the foundation, and inspect the attic for signs of damp insulation. What you shouldn’t do is remove siding, cut into drywall seams, or attempt any structural repair on a failing addition. Once you open a wall cavity, you’re liable for whatever you find, and if the framing is compromised, you’re now dealing with load-bearing issues. That’s the line where a homeowner should stop and a licensed contractor should take over. If you’re seeing the signs above, call us at (213) 277-6578 and we’ll do a full assessment. The estimate is free, and you’ll know exactly what you’re dealing with before you spend a dollar.
FAQs
A properly built addition or ADU using CertainTeed materials should last 50 – 80 years for the structural framing, 30 – 50 years for the siding, and 20 – 30 years for the roofing depending on sun exposure and maintenance. What shortens that lifespan in Los Angeles is water intrusion at the transitions and poor original flashing work, not the CertainTeed materials themselves. If you’re seeing signs of failure at year 10 or 15, the issue is almost always the original installation, not the product. Call (213) 277-6578 and we’ll pinpoint what failed and what it’ll take to correct it.
Yes, in most cases. If the framing is sound and the problem is isolated to siding, flashing, or drywall, a targeted repair gets you another 20 – 30 years. Where rebuilds become necessary is when water has been moving through the wall for years and the studs and bottom plates are rotted or termite-damaged. We’ll open a small inspection area during the estimate and tell you honestly which path you’re on. The assessment is free, and you’ll have a written price either way.
A siding and flashing repair on a small ADU can be done in 3 – 7 working days. A full interior remediation with drywall, insulation, and refinishing usually takes 2 – 4 weeks. A complete rebuild of a failed addition can run 8 – 16 weeks depending on permitting and scope. We give you a real arrival window and a written schedule before we start, and we hit it. Call (213) 277-6578 to get a timeline for your specific project.
We keep common CertainTeed drywall and insulation products in our supply rotation, and we order siding, roofing, and specialty materials per project so you’re getting fresh stock with full manufacturer warranty. We also work with KraftMaid cabinetry, Cambria and Silestone countertops, and other recognized brands, so the finish materials in your addition or ADU carry their own manufacturer warranties alongside our 365-Day Done Right Promise. If anything we install fails inside that guarantee period, we come back and make it right at no charge, in writing, on every project.
Written by Trevor Nash, Owner, Penhallow Remodeling Los Angeles at Penhallow Remodeling Los Angeles, serving Los Angeles and nearby areas.
