Tamko Home Additions & ADU Nationwide

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

Tamko home additions and ADU projects in Los Angeles typically run $53,100 to $153,400 for a full build, depending on square footage, foundation type, and whether you’re converting a garage or building new. Most homeowners start calling us when they realize their current space isn’t working anymore: a guest room that’s become a storage closet, a garage that hasn’t held a car in five years, or a home office squeezed into a corner of the living room. You’re not looking for a whole new house. You’re looking for the right way to add square footage to the one you’ve got.

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Here’s the reality of Tamko-related additions in Southern California: Tamko is a roofing and waterproofing manufacturer, so when we talk about “Tamko home additions” in Los Angeles, we typically mean additions and ADUs that tie into existing Tamko roof lines or use Tamko underlayment and flashing systems. Getting the roof integration right on an addition matters more than almost anything else, because Los Angeles sees real rain in winter months and serious sun exposure the rest of the year. Penhallow Remodeling is an independent general contractor, not affiliated with Tamko, but we spec their waterproofing products on additions where the roof pitch or tie-in calls for it.

Which Tamko Models This Applies To

When an addition or ADU connects to your existing roofline, you’re working with whatever Tamko system was installed on the original structure. In Los Angeles, that’s usually Tamko Heritage shingles, Tamko MetalWorks steel panels, or Tamko TW-60 underlayment on flat-roof portions common in mid-century homes around the Valley. The compatibility question isn’t about matching the addition to a specific Tamko shingle color, though that matters. The real question is whether the roof tie-in was flashed and underlayed correctly so water never finds a seam.

For a garage conversion ADU, the original roof rarely gets touched except at the edges where new framing meets old. But for a second-floor addition or a bump-out, you’re cutting into the existing Tamko roof and marrying new rafters to old ones. That’s where we see the most problems from other contractors: underlayment laps done backwards, flashing nailed too close to the corner, or the new roof pitch too shallow for the original Tamko shingle warranty to apply. We identify what’s on your roof by pulling a shingle and checking the manufacturer stamp on the underside, or matching the profile against Tamko’s current Los Angeles distributor stock. Aftermarket equivalents exist, but on a project this size, OEM Tamko underlayment and flashing costs $400 to $1,800 extra and eliminates the warranty argument entirely.

Signs Your Tamko Home Additions & ADU Is Failing

• Water stains on the ceiling where the addition meets the original roofline. This is the most common failure we see in Los Angeles additions built in the last ten years. The flashing wasn’t stepped correctly, or the underlayment was lapped the wrong direction, and winter rains find the gap.
• Drywall cracks running diagonally from the corner of the new opening. On additions and ADUs, this usually means the foundation wasn’t tied to the original slab properly, or the header over a new beam is undersized. Los Angeles soil expands and contracts with moisture, and a poorly connected addition moves independently.
• Doors that stick in summer and swing freely in winter. Wood framing in an uninsulated ADU absorbs moisture from coastal air and releases it during Santa Ana heat. If the door frames weren’t installed with the right gap tolerances, you’ll feel the difference seasonally.
• Musty smell that gets worse after rain, especially near the baseboards. This points to flashing failure at the roof-to-wall junction or missing kickout flashing where a roof eave meets a sidewall. In Los Angeles, that water travels down inside the wall cavity and shows up as odor long before you see staining.
• Visible daylight through the soffit-to-roof transition inside the attic. Get up there with a flashlight on a sunny day. If you can see light where the addition roof meets the original structure, the underlayment or decking was cut short and your addition has been breathing outside air and moisture since day one.

Replacement Cost & What’s Included

For a full home addition in Los Angeles, the range is $53,100 to $153,400, and ADU construction runs $106,200 to $259,600 for a detached unit with kitchen and bath. Garage conversions fall in the middle at $35,400 to $94,400. Where your project lands depends on square footage, whether you need foundation work (most Los Angeles hillside lots do), and how much of the existing roof and framing has to be rebuilt to tie in correctly.

What drives cost higher is not usually the Tamko materials themselves. It’s the structural work: shear walls, beam sizing, and foundation doweling to meet Los Angeles building code. A written price from us includes everything: demo, framing, roofing, drywall, paint, electrical and plumbing rough-in, permits drawn and pulled, and final inspection. You’ll never see a change order for something we should have caught in the estimate. The 365-Day Done Right Promise applies to every addition and ADU we build. If something fails inside that year, we’re back to fix it at no charge, and that’s in writing before the first wall goes up.

DIY or Call Us?

You can walk your own roofline and check for lifted Tamko shingles, missing flashing, or visible underlayment edges. You can look in the attic for daylight and dark stains on the decking. Those are safe checks that tell you whether a professional inspection is worth scheduling. What you shouldn’t do is pull apart a roof-to-wall junction on a two-story addition or wedge yourself into a crawlspace under an existing ADU to check foundation bolts. That’s how homeowners get hurt, and it’s how small problems become five-figure repairs.

If you’ve got water stains, sticking doors, or cracks that worry you, call us at (936) 259-2607. We’ll send someone who knows what to look for, and we’ll give you a written report with the price to fix what’s actually wrong. Give me the whole picture first, then we pick up the tools.

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