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GAF Home Additions & ADU: The Los Angeles Owner’s Guide
A GAF home addition or ADU in Los Angeles typically runs $53,100 to $153,400 installed, and most projects take 16 to 30 weeks from permit submittal to final inspection. We stock GAF-rated roofing, underlayment, and weatherization components for additions and ADUs, and we can start the framing and roofing phase as soon as your city permit is approved. Most owners call us after a contractor disappears mid-framing, after a first-roof leaks in the first winter rain, or when a city inspector flags non-compliant work and the original crew won’t answer the phone.
Which GAF Models This Applies To
GAF doesn’t sell a single “home addition” product. What matters on an addition or ADU is the GAF roofing system you spec: Timberline HDZ or UHDZ architectural shingles, Camelot II for a heavier profile, or TPO membrane if your ADU roof is low-slope. The compatibility question that trips up owners is this: GAF’s warranty depends on using the full system, not just the shingle bundle. That means GAF underlayment (Deck-Armor or Tiger Paw), GAF starter strips, GAF ridge cap shingles, and GAF ventilation. Mix a GAF shingle with off-brand felt and the manufacturer warranty shrinks, sometimes to nothing. We spec the complete system because a partial warranty is a warranty in name only. As an independent contractor, Bradford Remodeling is not affiliated with GAF. We buy GAF materials through authorized distributors, which keeps the warranty structure intact without pretending to be a factory arm.
Styles & brands we work with
Signs Your GAF Home Additions & ADU Is Failing
- Water staining at the ceiling-to-wall transition of the addition. This usually means the flashing at the new roofline was lapped wrong, or the crew reused flashing from the old roof. Water follows the seam, and the stain shows up in the addition’s corner first.
- Roof shingles lifting at the ridge of the new addition within the first year. Ridge cap shingles need proper nailing and often get rushed on punch-out day. In Los Angeles, Santa Ana winds find loose ridge caps fast.
- Doors or windows in the new space binding within months of completion. The addition’s foundation settled differently than the original house, or the framing wasn’t dried in level. Binding is a framing and foundation issue, not a hardware issue.
- Drywall cracks at the seam where the addition meets the original house. Some degree of settling is normal, but cracks wider than a paint line in the first year suggest the connection detail wasn’t properly flashed or isolated.
- The ADU feels damp or smells musty even in dry weather. Underslab vapor barrier or crawlspace venting was skipped. In Los Angeles, where most people assume “it never rains so moisture isn’t a problem,” this is exactly the failure that shows up later.
See the difference
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After
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After
Before
AfterReplacement Cost & What’s Included
A full GAF-roofed home addition in Los Angeles runs $53,100 to $153,400, depending on square footage, foundation work, and whether the addition includes plumbing. A detached ADU runs higher, $106,200 to $259,600, because the foundation, utility trenching, and kitchen or bath rough-in all start from zero. Here’s the line item breakdown for the roofing component specifically, which is where GAF product selection lives:
- GAF Timberline HDZ shingle roof on a new addition or ADU: $9,440 to $23,600 depending on roof area and pitch.
- GAF TPO membrane for a low-slope ADU roof: $8,260 to $17,700.
- GAF Deck-Armor underlayment with full system components: included in the roof line; we don’t bid it separately.
- Framing and dry-in (substrate prep, flashing, ventilation): $11,800 to $35,400 depending on complexity.
The number we give you before work starts includes parts, labor, permits, and the written 365-Day Done Right Promise. If the roof fails inside that year, we return and correct it at no charge. No change orders at the door. No re-quote after demo. That’s The Garrison Standard: a written price before any work starts, every time.
DIY or Call Us?
Roofing an addition is not a weekend project, and neither is the framing under it. The dangerous parts are height work, framing loads, and weatherizing a new roof plane correctly. A fall from a second-story addition roof is the kind of injury that ends careers and lives. We’re not saying you can’t inspect. You can. Check for lifted shingles after wind events, look at the ceiling for water stains, and photograph any visible gaps at the seam where the addition ties into the original house. But once you’re talking about stripping shingles, pulling flashing, or re-framing a wall, you need a trained crew. If you’ve got a failing addition roof and want it done right the first time, call (903) 568-7222 for a free estimate. A live person answers, not a voicemail tree.
FAQs
A properly installed GAF Timberline HDZ roof on a Los Angeles addition lasts 25 to 30 years, though the real variable is the underlayment and flashing, not the shingle itself. Los Angeles roofs die young from UV beating and Santa Ana wind, not from rain. With the full GAF system and proper ventilation, 25 years is a reasonable floor. Call (903) 568-7222 for an inspection if your addition roof is past year 20.
Sometimes, yes. If the failure is localized, a flashing repair or a ridge cap replacement can solve the problem for a few hundred dollars. If the underlayment was skipped or the sheathing is rotting, patching won’t hold. We’ll tell you which one you have, with a written price either way.
A typical addition re-roof in Los Angeles takes 3 to 5 working days from tear-off to final inspection, assuming the framing beneath is sound and the weather cooperates. If framing repair is needed first, add 1 to 2 weeks depending on scope.
We stock common GAF accessories, starter strips, and ridge cap shingles for service calls on existing additions and ADUs. Full roof system materials are ordered per project from local Los Angeles distributors so the shingle lot numbers match and the warranty stays intact.
Written by Curtis Lane, Owner, Bradford Remodeling at Bradford Remodeling, serving Los Angeles and nearby areas.
