IKO Underlayment & Deck Repair in Chicago, IL

IKO Underlayment & Deck Repair: The Chicago Owner’s Guide

IKO underlayment and deck repair in Chicago typically runs $380-$720 for standard residential sections, with most jobs completed same day. We stock IKO-compatible synthetic underlayment, ice-and-water shield, and oriented strand board (OSB) decking on every truck, so we’re not making a supply run while your attic takes on water. Most homeowners figure out something’s wrong when they spot a ceiling stain after a hard wind off the lake, or when their upstairs bedroom smells like wet cardboard in February.

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Which IKO Models This Applies To

This applies across IKO’s full residential lineup: Cambridge architectural shingles, Dynasty performance shingles, Marathon 25 three-tabs, and Royal Estate premium laminates. The underlayment beneath these systems is where the real protection lives, and IKO’s recommended synthetic underlayment runs 48 inches wide at roughly 16-20 mils thick, depending on whether your original installer used IKO’s own Pro4 system or a generic felt substitute.

Here’s how to tell what you’ve got. Pop your attic hatch on a dry day and look for printed markings on the underlayment itself. IKO-branded synthetics carry a lot number and the IKO logo; if you see plain black felt or an unmarked gray sheet, you’re likely looking at a non-OEM install. For deck repair, measure the thickness of your existing OSB or plywood: Chicago code since 2015 requires 7/16-inch minimum OSB or 15/32-inch plywood on pitched roofs, but plenty of older homes in neighborhoods like Portage Park or Austin still have 3/8-inch that warps and delaminates after repeated freeze-thaw.

We install OEM IKO underlayment where it makes sense, but we’ve also sourced a synthetic equivalent from the same mill that produces IKO’s private-label stock. It carries the same 15-year warranty and costs 12-18% less. We’ll tell you which we’re proposing and why. Ridgeline Roofing Co. of Chicago is an independent service provider, not affiliated with IKO.

Signs Your IKO Underlayment & Deck Repair Is Failing

• Ceiling stains that grow after northeast wind events. Chicago’s lake-effect storms drive water sideways. When underlayment laps are improperly sealed or the ice-and-water shield stops short of the eave edge, water finds the gap. The stain is your deck telling you it’s been wet more than once.
• Sagging or spongy decking near chimneys and vent stacks. These are the first deck sections to fail because they’re cut, flashed, and rarely inspected. OSB swells when it gets wet, then the fibers separate. Step lightly in the attic; if the deck moves underfoot, the damage is already structural.
• Granules in the gutter but no visible shingle damage. When underlayment traps moisture against the deck, the back of the shingle delaminates prematurely. The granules wash off before the shingle itself looks cracked. We see this often on north-facing slopes in Oak Park and Evanston where sun never fully dries the roof.
• Ice dams forming above heated walls every winter. Poor underlayment sealing at the wall-roof junction lets warm, moist air hit cold sheathing. The freeze-thaw cycle builds ice, and the real problem is under the shingles where you can’t see it.
• Daylight visible through the roof boards from inside the attic. This means the decking itself has rotted through or pulled from fasteners. It’s not just an underlayment issue anymore; the structural deck needs replacement before anyone walks that slope safely.

Replacement Cost & What’s Included

What moves you within these ranges: deck thickness (7/16-inch OSB costs more than 3/8-inch but is what we spec), accessibility (steep pitches in Lincoln Park’s older housing stock take longer), and whether we’re matching existing IKO shingles or integrating with a different brand. Our quote includes removal, disposal, new underlayment or decking, and reinstallation of your existing shingles where they’re salvageable. The 90-Day Done Right Promise covers the workmanship: if it leaks, we come back. No paperwork, no arguing. A square deal: the price we quote is the price you pay.

DIY or Call Us?

There’s a short list of things a homeowner can safely check. From inside your attic, trace the water stain uphill to its highest point. Note whether the deck feels solid or gives under hand pressure. Photograph any visible underlayment branding. That’s about where the safe DIY ends.

Deck repair and underlayment replacement means working on a pitched surface, often with compromised footing where the deck itself is rotted. Chicago’s municipal code requires a permit for deck replacement exceeding 25% of the total roof area, and most homeowners’ insurance policies won’t cover fall injuries during self-performed roofing work. We’ve also seen well-meaning owners tear off shingles to reach the underlayment, then discover the entire slope needs rescheduling when rain rolls in off Lake Michigan that afternoon. We carry full workers’ compensation and general liability, and we don’t leave a roof open overnight. Call (855) 641-3418 if you want an honest assessment of whether this is a patch, a section, or a conversation about the whole system.

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