IKO Home Additions & ADU Nationwide

IKO Home Additions & ADU: The Riverside Owner’s Guide

If you’re dealing with a failed or failing IKO home addition or ADU component in Riverside, the fixed-price range for a full replacement on a standard scope runs $45,000 to $130,000, depending on square footage, foundation type, and site access. We stock IKO-compatible structural materials and can typically begin the teardown and rebuild within your project window once the plan set is approved. Most Riverside homeowners discover the failure the hard way: a soft spot in the floor joist, a roofline that’s begun to sag, or a permit inspection that flags substandard framing from a prior contractor’s work.

Call (424) 567-8472

We’re an independent remodeling contractor serving Riverside and nearby communities, and we are not affiliated with IKO. What we know is how their envelope products perform in Southern California’s heat and dry spells, and what fails first when water or sun gets past the membrane.

Which IKO Models This Applies To

IKO’s product line spans roofing underlayments, ice-and-water barriers, and synthetic felts that get installed during a home addition or ADU build in Riverside. The compatibility question matters when a prior addition was framed and flashed with a specific IKO product, and now you’re extending the roofline or tying into the existing rake. The most common issue we see on Riverside additions from the 2000s and early 2010s is an underlayment that was spec’d for a low-slope condition but installed on a steeper pitch. That mismatch leads to early breakdown at the lap seams in the heat of a Riverside summer, when attic temperatures can sit above 130°F for weeks. If you can still read the product code on the selvedge edge of the original roll, that tells us the exact series and whether we can match it with an OEM roll or need to go to an equivalent aftermarket membrane with a compatible exposure rating. The short version: IKO’s StormShield and Armourbase lines are the ones we most often match on residential addition scopes in Riverside, and the aftermarket equivalent should carry the same ASTM D1970 rating before we will put our name on it.

Signs Your IKO Home Additions & ADU Is Failing

• Water staining at the ceiling-to-wall junction. This is the tell that the underlayment has delaminated at a lap joint, and water is traveling along the framing instead of shedding to the gutter. Riverside’s winter rain events, short and hard as they are, expose this fast.
• Granule loss showing in the valley metal. When the underlayment under the valley fails, the granules from the shingles above start to wash out and collect at the downspout. That’s not cosmetic. It means the water path has been compromised.
• Peeling paint or efflorescence on the new addition’s exterior wall. Water wicking behind the stucco or siding means the wall flashing, not the roof, is the breach. On ADU tie-ins we inspect the step flashing first.
• Attic sheathing feels spongy at the soffit line. Riverside’s humidity swings between the dry inland air and Santa Ana-driven dryness, but a compromised underlayment traps dew at the eaves. If the OSB gives under your thumb, the substrate is done.
• Daylight visible at the ridge from inside the attic. That is a straight-up installation failure, and we see it more often than we should in Riverside additions from non-permitted work. It means the ridge cap was nailed to the underlayment, not the framing.

Replacement Cost & What’s Included

For a Riverside home addition or ADU rebuild, you’re looking at $45,000 to $130,000 installed. That is not a vague range to make you call. The spread comes down to three things: whether the addition sits on a raised foundation or slab, how much of the existing framing can be salvaged, and whether the roof ties into the main house or stands separate. A small 400-square-foot bedroom bump-out on a slab with a simple gable roof lands at the bottom of that range. A full ADU with a new kitchen rough-in, separate meter panel, and a roof tie-in to the primary dwelling will push toward the top. Every proposal from us includes a written line-item price before any work starts, and the 365-Day Done Right Promise in writing. If something we installed fails inside that first year, we come back and fix it at no charge. That is the whole point of The Garrison Standard: the price is in writing, the scope is in writing, and the guarantee is in writing. Nobody from our crew shows up and re-prices at the door.

DIY or Call Us?

You can safely inspect a few things yourself: look for water staining at ceiling corners, check whether your addition’s downspouts discharge at least three feet from the foundation, and go into the attic on a sunny day to check for light penetration at the ridge. What you should not do is pull up underlayment or cut into wall flashing. You are working at height, and the roof membrane under tension can kick back when you pry it. Riverside’s building code also requires permits and inspections for any structural modification to an addition or ADU. Curtis Lane, our owner, keeps a copy of the current California Building Code in his truck, and he has pulled it out mid-conversation more than once when an owner tells us a previous contractor said “no permit needed.” A wrong fix in this situation costs more than the original repair. If the scope is more than a visual check, call us at (424) 567-8472 and we’ll send a background-checked, uniformed technician. Written estimate, no charge.