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Owens Corning Home Additions & ADU: The San Diego Owner’s Guide
If you’re planning an Owens Corning home addition or ADU in San Diego, the full installed cost typically runs $53,100 to $153,400 depending on square footage, foundation type, and utility connections. Mason Remodeling Co San Diego works with Owens Corning insulation and roofing systems throughout every addition we build, and we deliver a written line-item price before any work starts. Homeowners usually reach out after realizing their existing home can’t accommodate a growing family, an aging parent, or a rental-income opportunity, and they want to know exactly what it costs before committing.
Owens Corning’s role in an addition or ADU isn’t a single “part” that fails. It’s the insulation, roofing underlayment, and attic ventilation systems that keep the new space comfortable and protected. San Diego’s coastal moisture and inland heat make these systems work hard, and when corners get cut on insulation or roof decking, you feel it within the first summer or winter.
Which Owens Corning Products Apply
Owens Corning doesn’t manufacture a “home addition” product line. What you’re actually selecting is a combination of Owens Corning building products that go into the addition or ADU: batt and blown-in insulation (specific R-values determined by California’s Title 24 energy code), attic ventilation (ridge vents, intake vents), and in most San Diego additions, Owens Corning roofing shingles or underlayment tied into the existing roofline.
The compatibility question that matters most is: what is already in your home, and how does the new construction tie into it? If your existing roof is Owens Corning Duration shingles, the addition’s roof plane should match or be deliberately contrasted. If your attic currently has R-38 blown-in fiberglass and the addition only gets R-19, you’ll feel the difference in the room directly below. We check the existing product labels during our estimate. The product code is printed on the shingle wrapper edge and stamped into the insulation facing, which tells us exactly what was installed before.
For the OEM versus aftermarket decision: Owens Corning insulation has a limited lifetime warranty only when installed by an Owens Corning-certified contractor and registered with the manufacturer. Off-brand insulation may cost 15 to 20 percent less at the supply house, but the failure mode in San Diego is what lands in the walls. Owens Corning’s fiberglass batts resist the moisture-driven settling we see in homes near Mission Bay and Ocean Beach, where salt air and humidity work their way through the building envelope. We stock Owens Corning on the truck and quote it as the default.
Styles & brands we work with
Signs Your Home Addition or ADU Is Failing
Before calling us, look for these issues in the structure you already have or the one you’re considering:
- Hot rooms in the new addition, especially in July through September. This usually means insulation was compressed during installation, leaving air gaps at the top plates or around outlets. A thermal camera reads it in minutes.
- Mold or mildew smell in the ADU’s closet or bathroom wall. Improperly sealed sheathing or missing insulation at the floor rim lets San Diego’s coastal air find its way inside and condense. We see this most often in garage conversions near Point Loma and Pacific Beach.
- Shingles lifting or granule loss on the addition’s roof within five years of construction. Often caused by inadequate attic ventilation. Owens Corning shingle warranties assume proper airflow, and without ridge and soffit vents working together, the roof cooks from underneath.
- Higher utility bills than expected after the addition is complete. California Title 24 requires specific insulation values, but a lot of unpermitted additions skip the inspection that enforces it. We’ve corrected R-13 walls where R-21 was required, and the homeowner noticed the difference on the next SDG&E bill.
- Rattling windows or drafts near the new construction’s junction with the old wall. The transition point between old framing and new framing is rarely flashed and insulated correctly on cheaper jobs, leaving a six-inch gap that leaks conditioned air year-round.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
For a full Owens Corning-insulated home addition in San Diego, budget $53,100 to $153,400. An ADU with foundation, kitchenette, and bath runs $106,200 to $259,600, depending on whether it’s attached, detached, or a garage conversion (garage conversions range $35,400 to $94,400 in San Diego County).
Here is how the numbers break down for the Owens Corning-related scope within an addition or ADU:
- Owens Corning batt insulation (walls and ceiling, R-15 to R-38): $1,180 to $4,720 depending on square footage and cavity depth
- Attic ventilation package (ridge vent, soffit vents, baffles): $590 to $1,770
- Owens Corning roof decking and underlayment on the new roof plane: $2,360 to $9,440
- Owens Corning Duration shingles on the new roofline (if applicable): $7,080 to $17,700
Every quote from Mason Remodeling Co San Diego includes the full parts price, labor, permits, dump fees, and the 365-Day Done Right Promise: if it isn’t right within a year of completion, we fix it at no cost.
DIY or Call Us?
Replacing the Owens Corning insulation or reworking the roof on an existing addition is not the place to save money. The work involves crawl spaces, attic rafters, and in the case of roof systems, heights and tear-off that can injure you fast. If your interest is checking what is already there, you can certainly peel back a piece of trim and see whether insulation fills the cavity or leaves a void. You can also walk the attic and look for gaps at the soffit line. That’s about as far as we’d encourage anyone to go.
What goes wrong with DIY is what we get called to fix: batts shoved in too tightly (compressed R-value drops by up to 30 percent), or ventilation added without understanding intake-to-exhaust ratio, which creates negative pressure that pulls more moisture into the attic. “Tell me what’s broken. I’ll tell you what it takes.” That’s Isaac Pruett’s rule, and it applies every time we open up a wall in San Diego. Call (619) 673-9302 for a free estimate, and we’ll tell you exactly what’s in the walls and what it’ll cost to make it right.
FAQs
How long should Owens Corning insulation last in a San Diego addition?
Owens Corning fiberglass insulation should last the life of the structure when installed correctly and kept dry, which means 30-plus years in San Diego’s climate. What shortens it is moisture or rodent activity, common in older crawl spaces and garages. We also work with KraftMaid and Cambria products in built-out ADU spaces, and the same airtight-installation standard applies.
Can a failing addition be repaired instead of rebuilt?
In most cases, yes. The repair usually involves opening the affected wall or ceiling, removing compromised insulation, sealing the air gaps, and reinstalling Owens Corning batts at the correct R-value. The cost runs roughly $945 to $3,540 per affected room in San Diego depending on wall size and whether retexturing is required. Call (619) 673-9302 and we’ll quote it room by room.
How long does an Owens Corning insulation replacement take?
For a standard ADU or single-room addition, one day for removal and reinstallation, plus half a day for drywall repair depending on how much we had to open. Larger whole-addition retrofits run two to three days. The written estimate includes a schedule so you know exactly when we arrive and when we’re done.
Do you stock Owens Corning insulation on the truck?
Yes. Our crews carry Owens Corning batts in the most common R-values for San Diego additions (R-13, R-15, R-21, R-38) and we source specialty sizes from our supply partners within one business day. For Silestone or Cambria surfaces in the finished ADU, we special-order and schedule delivery to align with the build.
Written by Isaac Pruett, Owner, Mason Remodeling Co San Diego at Mason Remodeling Co San Diego, serving San Diego and nearby areas.
