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IKO Home Additions & ADU: The West Covina Owner’s Guide
IKO home additions and ADU projects in West Covina typically run $45,000 to $130,000 for a full addition, with detached ADUs landing between $90,000 and $220,000 depending on size, site access, and finish level. We handle the whole scope: foundation, framing, roofing (using IKO-compatible underlayment and flashing details), electrical, plumbing, drywall, and finishes. The reason most owners call us isn’t a single “part” that failed in the traditional sense. It’s usually a sequence: they find water staining at a roof-to-wall intersection on an existing addition, notice the stucco pulling away at the corner, or discover the permit was never finalized on an unpermitted conversion they bought into. The “part” that fails is almost always the integration point, and that’s exactly what this page helps you sort out.
Which IKO Models This Applies To
IKO manufactures roofing and waterproofing products, not structural framing systems, so when we talk about IKO home additions and ADU work in West Covina, we’re talking about the roofing and weatherproofing layer that ties the new structure to the old one. The IKO product lines that matter here are their asphalt shingle lines (Cambridge, Dynasty, Nordic, Royal Estate), their underlayments (ArmourGard, GoldShield), and their ice-and-water shield products. The compatibility gotcha most homeowners miss: an addition roof must tie into the existing roof plane with the same or better underlayment class, and in West Covina’s hot summers, IKO’s ARMA-compliant shingles need proper attic ventilation or you’ll cook the sheathing in five to seven years. If your addition or ADU was built before roughly 2015, it may have older IKO Marathon or discontinued lines on it, and matching those exactly is a parts problem: the color granules fade differently than current production runs, so a patch job will show. We’re an independent service provider and not affiliated with IKO, which means we can source the current IKO product or a quality aftermarket equivalent and tell you honestly which one makes sense for your roof plane.
Styles & brands we work with
Signs Your IKO Home Additions & ADU Is Failing
- Water staining at the roof-to-wall junction. This is the number one failure we see on additions in West Covina. The flashing that should bridge the old roof plane and the new wall either wasn’t installed correctly or has pulled away after a few seasons of thermal expansion. The stain is the symptom; the failed flashing is the cause.
- Granule loss in the gutters near the addition. IKO shingles shed granules over time, but if you’re seeing a heavy concentration of granules in one downspout after the first five years, the shingles on that new roof plane are degrading faster than they should. Usually that’s an attic ventilation issue cooking them from underneath.
- Stucco cracking at the addition’s outside corners. A properly tied addition moves as one structure. If you’re seeing vertical cracks at the corner where the new wall meets the old, the foundation or framing connection is shifting. This is a structural issue, not a cosmetic one.
- Doors or windows in the addition that stick seasonally. A little movement is normal in California’s dry-wet cycles, but if a door in the new room jams every winter and frees up every summer, the header or the foundation is moving more than it should be.
- Musty smell in the ADU after rain. That’s trapped moisture in the wall cavity or under the floor. On unpermitted conversions especially, we find missing vapor barriers and incorrect IKO underlayment detailing that let water in and then hold it there.
See the difference
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After
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After
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AfterReplacement Cost & What’s Included
For IKO home additions and ADU work in West Covina, installed pricing runs from $45,000 for a small bump-out or single-room addition up to $130,000 for a larger multi-room addition. Detached ADUs start at $90,000 and can reach $220,000 once you factor in separate utility runs, site work, and a full kitchen and bath. What drives the range: the square footage, whether you’re tying into an existing roof plane or building a standalone structure, the condition of the existing foundation, and the finish level you want inside. We write a line-item price before any work starts, so you’ll see exactly what’s allocated to framing, roofing, electrical, plumbing, finishes, and permits. No change orders, no surprises at the end. Every completed project carries a written workmanship warranty, plainly stated with what’s covered and for how long.
Key Takeaways:
- Full addition in West Covina: $45,000 – $130,000; detached ADU: $90,000 – $220,000
- Written line-item price before any work starts, on every project
- Permits pulled by us, inspections passed, final sign-off in your hands
- 365-Day Done Right Promise covers workmanship for a full year from completion
DIY or Call Us?
There are a few things you can safely check yourself before calling anyone: look for visible water staining at the roof-to-wall junction, check the gutters for heavy granule accumulation, and note whether doors stick seasonally. Those observations will save time on the phone. What you shouldn’t do is get on a ladder and start pulling shingles or flashing to “see what’s under there.” Roof work on a sloped plane, especially a tie-in with a living space below, is dangerous. We’ve seen homeowners make a small flashing issue into a serious water intrusion by loosening the wrong course of shingles. If the addition or ADU roof is leaking, call (707) 760-7579 and we’ll send someone out to look. The estimate is free.
FAQs
An IKO asphalt shingle roof on an addition in West Covina should last 20 to 30 years if the attic is properly vented and the flashing details were done right. Poor ventilation is what shortens that to 10 to 15 years in this climate, because trapped heat bakes the shingles from the underside and accelerates granule loss and curling. Call (707) 760-7579 if you want us to check your venting; a quick attic inspection tells us a lot.
It depends on what’s failing. A flashing issue at the roof-to-wall junction can often be repaired for a few hundred to a couple thousand dollars, including removing and re-bedding the affected shingles. If the shingles themselves are losing granules across a large area or curling, patching buys you a year or two at most. We’ll tell you straight which situation you’re in, with photos, before quoting anything.
A standard single-room addition in West Covina takes roughly 10 to 16 weeks from permit approval to final walkthrough. A detached ADU with its own utilities typically runs 14 to 24 weeks. The permit phase here adds time that many owners don’t plan for, and we pull every permit ourselves so there are no surprises with the city’s review timeline. Call (707) 760-7579 for a realistic schedule for your specific scope.
We stock IKO-compatible underlayment, flashing materials, and common shingle colors on the truck, but we order the specific IKO shingle line and color to match your existing roof per job. That’s the only way to get a color and profile match that doesn’t look like a patch. We also work with KraftMaid, Cambria, and Silestone for the interior finishes on your addition or ADU, and we’ll walk you through those options in the showroom before you commit to anything.
Schedule your free estimate today. A live person answers every call, 24 hours a day, 7 days a week. Call (707) 760-7579 and we’ll set up a time to walk the property, talk through your options, and get you a written price. You should know what you’re getting before we ever pick up a tool.
Written by Isaac Pruett, Owner, Mason Remodeling Co West Covina at Mason Remodeling Co West Covina, serving West Covina and nearby areas.
