IKO Home Additions & ADU Nationwide

IKO Home Additions & ADU: The Los Angeles Owner’s Guide

IKO-compatible roofing components for home additions and ADUs in Los Angeles typically run $531-$2,125 for repair and $9,440-$23,600 for full replacement, with most IKO Cambridge, Marathon Plus, and Dynasty series shingles matched from our stocked inventory. We carry common IKO accessories - ridge caps, starter strips, synthetic underlayment, and ice-and-water shield - for same-day installation on addition tie-ins and ADU roof assemblies across Los Angeles. Most homeowners discover a problem when the new addition’s ceiling shows water staining after the first winter rains, or when the ADU’s IKO shingles curl at the edges while the main house’s roofing stays flat, signaling a batch mismatch or improper attic ventilation in the smaller structure.

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Which IKO Models This Applies To

IKO’s three residential lines show up regularly on Los Angeles additions and ADUs: Cambridge Architectural (laminated, 240 lbs per square), Marathon Plus (traditional 3-tab, 200 lbs per square), and Dynasty (heavyweight laminated, 250 lbs per square with ArmourZone reinforcement). The model number prints on the back of individual shingles in faded ink, but the easier check is the bundle wrapper color - blue for Cambridge, green for Marathon Plus, red for Dynasty - which most Los Angeles suppliers still use consistently.

The compatibility gotcha on additions: IKO changed its Cambridge sealant strip width in 2019 from 1-1/4 inch to 1-1/2 inch. If your original roof is pre-2019 Cambridge and you’re tying in a new addition, the new shingles won’t nest correctly at the rake edge without a starter strip adjustment. We stock both sealant configurations and the IKO Leading Edge Plus starter strip that bridges the gap. For ADUs under 800 square feet, the Dynasty line’s weight can stress standard 7/16-inch OSB roof decking; we check the span rating stamped on the existing deck before quoting, because upgrading to 5/8-inch plywood adds $1.80-$2.40 per square foot but prevents the “oil-canning” bounce that telegraphs through the finished ceiling.

OEM IKO parts versus aftermarket: IKO’s own ridge cap (Hip & Ridge 12) costs roughly 15% more per bundle than Atlas or CertainTeed equivalents, but the color match is exact and the laminate thickness matches the field shingle profile. On visible front elevations in Los Angeles neighborhoods like Hancock Park or Los Feliz, we quote OEM first and note the aftermarket option in writing. On rear-facing ADU roofs with limited sightlines, aftermarket saves money without the aesthetic penalty.

Signs Your IKO Home Additions & ADU Is Failing

• Granule loss exposing black asphalt. IKO Cambridge shingles in Los Angeles lose granules faster on south-facing ADU roofs where UV exposure peaks. The asphalt core cracks within 18-24 months of exposure, and water finds the crack before you see the leak inside. We check granule depth with a simple coin scrape - less than 1/8 inch remaining means replacement, not repair.
• Curling at the tab edges while the main house stays flat. This usually means the addition’s attic ventilation was skimped - IKO warranties require 1 square foot of net free vent area per 150 square feet of attic floor, and many Los Angeles ADU builders hit 1:300 by mistake. The trapped heat cooks the sealant strip from below. We fix the ventilation first, then resheet if the plywood is delaminated.
• Wind lift along the rake or ridge, especially after Santa Ana events. IKO’s standard sealant needs 70°F and direct sun to activate fully. Los Angeles additions built in winter sometimes get installed in 55°F weather, and the sealant never sets. The shingles look fine for months, then lift in the first strong wind. We hand-seal with IKO-approved asphalt plastic cement when the install temperature is below the manufacturer’s threshold.
• Water staining at the addition-to-house junction. The step flashing between old and new structures is the failure point, not the IKO shingle itself. But the repair requires lifting field shingles without damaging them, which is where having matching IKO stock matters. We document the existing shingle color with photos under neutral light before pulling anything.
• Sagging between trusses on the ADU roof. IKO Dynasty at 250 lbs per square on 24-inch truss spacing exceeds what 7/16-inch OSB is rated for in a 30-pound snow load zone - and Los Angeles building inspectors have started flagging this on ADU final inspections. The fix is sistering the trusses or upgrading the deck, neither of which is a shingle problem but both of which we catch during the IKO replacement quote.

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Replacement Cost & What’s Included

For IKO roofing on Los Angeles home additions, repair work runs $470-$2,125 depending on how many square feet need removal and whether the plywood deck is sound. Full replacement on an addition or ADU roof falls between $9,440 and $23,600, with most 600-1,200 square foot ADU roofs landing in the $12,000-$16,000 range using IKO Cambridge with standard underlayment.

The range driver is deck condition. We strip to the sheathing, photograph every sheet, and quote plywood replacement at $85-$120 per 4×8 sheet installed - no surprises. Under Clause 1 of the Haven Standard, that written price includes IKO shingles, synthetic underlayment, drip edge, ridge vent or static vents, permit fees, and disposal. If we find rot in the fascia or rafter tails once we’re open, work stops, photos go to your phone, and a signed change order with the exact dollar impact sits on the table before anyone picks up a nail gun. That’s the discipline that has kept our projects within a few percent of the agreed number since 2007.

Our 365-Day Done Right Promise covers the installation and the IKO manufacturer’s limited warranty backs the product itself. The photo record - every sheet of decking, every vent location, every bundle lot number - goes to you as a PDF before we invoice.

DIY or Call Us?

There’s a safe middle ground for IKO roof checks. From the ground, use binoculars to scan for the granule loss and curling we described above. From a secure ladder at the eave, you can sight down the shingle plane for sagging or lifted tabs. Do not walk the roof - IKO’s sealant strips are slippery until fully cured, and the slope on most Los Angeles additions is steeper than it looks from below.

Where DIY ends: removing shingles to inspect step flashing requires disturbing the field course, and the IKO warranty is void if the reinstall isn’t done to their nailing pattern - six nails per shingle in high-wind zones, which Los Angeles is, with placement in the tar strip’s upper third. The nail gun depth matters too; overdrive cracks the shingle, underdrive leaves the head proud to catch wind. We’ve redone enough homeowner repairs where the leak stopped briefly, then returned worse because the nail pattern was wrong or the underlayment tear wasn’t patched. Call (213) 652-7670 and we’ll quote the inspection in writing - no charge for the visit, and if it’s a simple fix, we’ll say so.

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