IKO Underlayment & Deck Repair Nationwide

IKO Underlayment & Deck Repair: The Los Angeles Owner’s Guide

We stock and install IKO-compatible underlayment and replace rotted roof decking throughout Los Angeles, with most projects running $1,200 to $4,800 depending on how much decking has failed and which IKO underlayment your roof calls for. If you’ve spotted water staining on a ceiling, curling shingles at the eaves, or felt paper pulling away near a valley, the underlayment or the plywood beneath it has likely given out and needs a real fix, not a patch. Los Angeles homeowners usually discover this the hard way: a rainy week in January, a drip near the chimney, and a roofer’s camera showing plywood that’s turned to sponge.

Call (213) 521-8272

Here’s the part most people miss: the shingles are only the top layer. Under every IKO shingle is the underlayment, and under that is the deck, usually plywood or OSB. When the underlayment tears or ages out, water gets to the deck. When the deck rots, the nails lose their grip, and suddenly a small repair becomes a structural problem. We fix both layers, in that order, with written pricing before anything gets touched.

Key Takeaways

• IKO underlayment replacement in Los Angeles typically runs $1,200 to $4,800 installed, depending on deck damage.
• We stock IKO-compatible synthetic and felt underlayment on our trucks, plus CDX plywood and OSB decking for same-visit repairs.
• Deck rot is the expensive part. Catching underlayment failure early usually saves thousands.
• Every repair includes a written guarantee for 365 days, and a free second visit if our fix fails.

Which IKO Models This Applies To

This page covers underlayment and deck repair under IKO’s most common Los Angeles shingle lines: Cambridge, Dynasty, Nordic, and Royal Estate, plus the Crowne Slate and Armourshake profiles we see on hillside homes in Eagle Rock, Mount Washington, and Silver Lake. If your roof has IKO shingles, the underlayment underneath is almost certainly one of two types: IKO’s own RoofGard-Cool synthetic (a polypropylene sheet, tan on one side, with printed grid lines) or a standard ASTM D226 felt paper that a previous contractor substituted. Both fail differently, and we’ll tell you what’s actually up there before quoting anything.

Here’s the compatibility gotcha most homeowners don’t hear about: IKO’s synthetic underlayment is rated for specific fastener requirements. Nails with caps hold it, plain roofing nails tear through it over time, especially on steeper slopes. We’ve pulled back synthetic underlayment on Los Angeles roofs where every nail hole had elongated into a tear because the original installer used a cap nailer on the field but plain nails at the edges. That’s not a product defect, it’s an installation error, and it’s exactly what we look for.

On the OEM versus aftermarket question: we install IKO’s own underlayment when the job calls for it, but we also carry GAF, Owens Corning, and CertainTeed underlayment products that meet or exceed IKO’s installation specs. IKO’s warranty language doesn’t require IKO-brand underlayment under IKO shingles, but it does require underlayment that meets the same ASTM standards. We’ll show you the spec sheet if you want to see it. Mercer Roofing Co Los Angeles is an independent service provider, not affiliated with IKO, and we’ll match the right underlayment to your roof, not the other way around.

Signs Your IKO Underlayment & Deck Repair Is Failing

• Ceiling stains or drips after rain. Water has made it through the shingles, through the underlayment, and is now travelling along the deck to the lowest point. By the time you see the stain, the deck under that spot is already wet, and often soft.
• Wavy or sagging rooflines between rafters. This is rotted decking. Plywood delaminates and sags when it’s been wet repeatedly. Shingles follow the sag, and you get a visible dip that wasn’t there when the roof was new.
• Granules in your gutters with a fine, tan powder alongside them. The granules are from shingle wear, but the tan powder is often disintegrating underlayment. IKO’s synthetic and felt underlayments both shed material as they break down under Los Angeles sun exposure.
• Visible felt or synthetic sheeting at the eaves or in valleys. Wind-driven rain and repeated wet-dry cycles cause underlayment to pull back from the drip edge. Once you can see it from the ground, it’s no longer protecting the deck.
• Shingles that lift easily or nails that pop. When decking rots, nails lose their bite. The shingles might look fine from the ground, but if a repair technician can lift a shingle with one finger, the deck underneath is likely compromised.

Replacement Cost & What’s Included

In Los Angeles, expect to pay $1,200 to $2,800 for underlayment replacement with limited deck repair when the damage is caught early, and $3,200 to $4,800 when multiple sheets of rotted decking need to come out. The range depends on three things: how many square feet are involved, whether the deck is 3/8-inch plywood or heavier 5/8-inch or OSB, and how steep or cut-up the roof is. Access on hillside lots in Echo Park or Highland Park adds labor time, and we price that honestly rather than burying it in a change order you didn’t see coming.

Every quote we write includes parts and labor broken out line by line: underlayment material cost per square, decking sheet count and thickness, fasteners, removal and disposal of the old material, and the labor to pull and re-set the shingles. There’s no “we’ll see what we find” pricing on this. We inspect before we quote, we write the number down, and we do the work for that number. Every repair carries a 365-day written guarantee, and if our underlayment or deck repair fails within that year, the second visit is free. Grant Whitlock started Mercer in Los Angeles because he was tired of hearing from homeowners who’d paid twice for the same roof leak.

DIY or Call Us?

What you can safely do is inspect from the ground or from a ladder that’s fully secured: look for the sagging, the granule powder, the visible underlayment at the eaves. You can also check your attic on a dry day, look for water staining on the underside of the decking, and press a flat palm against the wood near the stain. If it gives, or if it feels spongy, that’s rot, not insulation dust. Those observations will help any roofer give you an accurate picture over the phone, and they’re genuinely useful to us when we quote.

What you should not do is pull shingles yourself, especially on a Los Angeles roof where the underlayment has already failed. Walking on a rotted deck is how people put a foot through a roof and into a ceiling joist. Then you’re looking at interior drywall repair on top of the roof work. We’ve seen it, and it’s never worth the money saved. The honest answer is that underlayment and deck repair is a two-person job with the right tools and the right fall protection, and we’d rather take that risk than have you take it. Call (213) 521-8272 if you want a straight answer about what’s under your IKO shingles and what it will cost to fix.

FAQs

Call Mercer Roofing Co Los Angeles for a Straight Answer

If you’ve got IKO shingles and a suspicion that the underlayment or deck underneath has failed, we’ll send a background-checked, uniformed technician whose name and photo you’ll have before they knock. They’ll badge in with a photo ID, inspect the roof, and hand you a written price for exactly what needs doing, no work starts without it. A live person answers our phone 24/7, and every repair is guaranteed in writing for 365 days. A roof should be the last thing on your mind, let’s keep it that way. Call (213) 521-8272 to schedule your free estimate.

Written by Grant Whitlock, Owner, Mercer Roofing Co at Mercer Roofing Co Los Angeles, serving Los Angeles and nearby areas.