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IKO Home Additions & ADU: The San Jose Owner’s Guide
When an IKO home addition or ADU component fails in San Jose, the cost to repair or replace it typically runs $53,100 to $153,400 for a full addition, and $106,200 to $259,600 for a standalone ADU build-out. We stock IKO-compatible roofing, ventilation, and flashing components used across home additions and ADU projects, and our crews can usually diagnose and quote the failing part same-day. Most San Jose owners first notice trouble as a water stain on the ceiling, a sagging roofline, or a draft that wasn’t there before the winter rains hit.
Before you tear into anything, know this: we’re an independent San Jose contractor. We’re not affiliated with IKO, but we know their product lines and how they perform in this climate. Curtis Lane and the Bradford Remodeling crew have worked on enough IKO-specified additions across Willow Glen and the Campbell border to know where these systems fail first, and what it takes to put them right. Here’s the straight number and the straight answer.
Key Takeaways
- IKO home addition and ADU repair or replacement in San Jose runs $53,100 – $153,400 depending on scope, structural condition, and materials.
- Most failures trace to ventilation, flashing, or substrate problems, not the IKO shingle or underlayment itself.
- You’ll get a written price before work starts. That’s not a courtesy, it’s the standard.
- Every completed job carries the 365-Day Done Right Promise. If it doesn’t hold, we come back. No charge.
Which IKO Models This Applies To
We work with IKO’s full roofing and weatherproofing line as applied to home additions and ADUs: the Cambridge architectural shingle series, Dynasty performance shingles, and the Nordic line for heavier coastal and hill exposure. For San Jose specifically, the Cambridge series is the most common IKO product we see on residential additions and garage-conversion ADUs. It holds to the manufacturer’s 110 mph wind rating when installed to spec, which matters on the east foothills and anywhere the Diablo winds pick up in fall.
Here’s the compatibility gotcha: IKO’s self-sealing adhesive strip needs clean, dry contact with the shingle below it, and in San Jose’s wet-winter, dry-summer cycle, we regularly see installs where the seal never fully set. That leaves shingles lifting within a season or two. If you’re matching an existing IKO roof on an addition, you’ll need the exact color lot code, not just the color name. IKO changes dye lots between production runs, and a “Charcoal Grey” from a 2022 run won’t match a 2025 run side by side. We pull the lot code from the original shingle wrapper or the under-eave label before ordering.
For underlayment and waterproofing on ADUs, we spec IKO’s StormShield and Armourbase products depending on the slope and the city of San Jose’s current code requirements for accessory structures. If the original build used an off-brand synthetic underlayment that’s now failing, we’ll replace it with IKO’s spec’d product rather than patch a failing system.
Styles & brands we work with
Signs Your IKO Home Additions & ADU Is Failing
- Water staining on the ceiling or wall joints – This is the number one call we get. By the time you see the stain, water has already moved through the roofing, the underlayment, and often the sheathing. On ADUs with vaulted ceilings, the stain can appear far from the actual leak point because water travels the rafter line before it drops.
- Shingle granule accumulation at the downspouts – IKO shingles lose granules as they age, and San Jose’s UV exposure accelerates that loss on south-facing slopes. If your downspout elbows are catching gravel-like grit, the shingles are past the midpoint of their life. The granules are what protect the asphalt from UV breakdown. Without them, the shingle matrix starts cracking within two to three years.
- Lifted or curled shingle edges after a wind event – This usually means the adhesive seal failed, often from install during a cool or damp stretch. IKO’s seal strip needs heat to activate. If the installer didn’t press or the temperature wasn’t right, the shingles never fully bonded. In San Jose’s fall wind season, those unsealed edges break loose and the lift starts.
- Mildew or musty smell inside the ADU during the rainy season – That smell is moisture sitting where it shouldn’t be. On ADUs with minimal attic space, a failing ridge vent or a blocked soffit vent traps warm, damp air against the underside of the sheathing. The IKO shingles may be fine. The ventilation system that protects them is not.
- Warped or sagging sheathing visible from the attic or crawl access – If the substrate is going, it’s not a shingle problem. It’s a water-management problem that’s been running for a while. On older San Jose ranch homes with additions from the 1970s and 80s, the original sheathing was often 3/8-inch plywood, which doesn’t have the stiffness modern IKO install specs call for. That’s a structural repair, not a patch job.
See the difference
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After
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AfterReplacement Cost & What’s Included
For an IKO roof or weatherproofing failure on a San Jose home addition, you’re looking at two cost bands. A repair-scope job, meaning shingle replacement, flashing correction, and ventilation fix on an existing addition, runs $470 to $2,125 for roof repair and $710 to $2,950 for tile roof repair if your addition used a tile accent. A full addition build, where the IKO components are part of new construction, runs $53,100 to $153,400. ADU construction with IKO-spec’d roofing and weatherproofing runs $106,200 to $259,600.
Here’s what drives the range on the repair side: the number of square of shingles, whether the substrate needs replacement, the slope and accessibility of the roof, and whether the underlayment is salvageable. We use the trade words straight: if the substrate is compromised, fixing the shingles on top of it is wasted money. We’ll tell you that up front.
Every quote includes parts, labor, debris removal, and the written 365-Day Done Right Promise. That means if the repair doesn’t hold inside a year, Bradford Remodeling comes back and corrects the work at no charge. The price you get before work starts is the price you pay when the job’s done. No numbers move at the door.
DIY or Call Us?
You can check your own gutter downspouts for granule accumulation. You can look at the shingle edges from ground level with binoculars. You can note where the water stains appear inside and when they started. Do that. It helps us diagnose faster when you call.
What you shouldn’t do is get on a ladder and start pulling up shingles, especially on a two-story addition or an ADU with a steep pitch. Roof work in San Jose means fall heights, and a wet shingle surface after the rain is a slip hazard that has put plenty of homeowners in the ER. If the sheathing under the shingles is wet or rotted, you’re not going to know until you’re standing on it, and that’s the wrong time to find out your roof can’t take your weight. This is a call-us situation. Straight number, written scope, done when we said done. Call (669) 272-2637.
FAQs
IKO architectural shingles typically last 22 to 28 years on a San Jose addition, but south-facing slopes in full sun will trend to the low end of that range, and a shingle with a failed adhesive seal can start lifting within two seasons. The microclimate matters, and so does the install. Call (669) 272-2637 if you’re seeing early granule loss or lifting, and we’ll tell you whether it’s a fix or a countdown.
If the shingles are intact and the problem is a flashing point or a ventilation deficiency, yes, we can repair it, typically for $470 to $2,125. If the substrate is compromised or the shingles are near end of life, a patch job is money you’ll spend twice. We’ll show you the condition of the substrate in the quote, not after we start tearing into it. Call (669) 272-2637 to schedule a look.
Most San Jose addition roof replacements take one to two working days for the removal and re-shingle, plus a half-day for flashing and ventilation correction. ADU roofs run a similar timeline. We schedule around weather windows in the winter months, because IKO’s adhesive seals need dry conditions to set correctly. Call (669) 272-2637 for a written timeline along with the written price.
We stock common IKO flashings, ridge vent sections, pipe collars, and starter strips on our trucks, along with IKO Cambridge shingle bundles in the colors most common to San Jose additions. For full re-roofs on larger additions or ADUs, we order the exact lot code from our supplier before the job starts so the color matches. Call (669) 272-2637 and we’ll confirm what we have and what we need to order.
Written by Curtis Lane, Owner, Bradford Remodeling Co at Bradford Remodeling Co San Jose, serving San Jose and nearby areas.
