Tamko Home Additions & ADU Nationwide

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

Tamko-compatible home additions and ADU construction in Los Angeles typically runs $53,100-$153,400 for a full addition, and $106,200-$259,600 for a detached ADU, depending on foundation type, utility tie-ins, and whether the existing structure needs seismic retrofitting. We stock Tamko roofing materials and compatible structural components on our Los Angeles trucks, and we can usually begin material staging within 48 hours of a signed scope. Most homeowners realize something’s wrong when the addition’s roofline doesn’t match the original pitch, or when water intrusion shows up at the tie-in seam between old and new construction after the first winter rains.

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Which Tamko Models This Applies To

Tamko doesn’t manufacture complete home addition or ADU structural systems - they’re a roofing and waterproofing materials supplier whose products get specified into addition builds across Los Angeles County. The relevant Tamko lines are the Heritage series architectural shingles, Titan XT impact-resistant shingles, and MetalWorks steel shingles, all of which we’ve installed on addition tie-ins from Santa Monica to Silver Lake. To identify what’s on your existing roof, look for the Tamko stamp on the shingle back, or check your permit file - Los Angeles requires roofing spec sheets with the building permit, and any addition permitted after 2015 should have them on record with LADBS.

The OEM-versus-aftermarket question matters less with Tamko than with some brands because their color blends are proprietary - “Rustic Slate” or “Weathered Wood” from another manufacturer won’t match. We source Tamko direct or through authorized Los Angeles distributors so the new addition roof matches the existing plane. If your original roof is discontinued, we document the closest current match in writing before ordering, because “close enough” is never a unit of measurement.

Signs Your Tamko Home Additions & ADU Is Failing

• Water stains on the ceiling where old meets new. The tie-in flashing wasn’t stepped correctly or the Tamko underlayment lapped wrong - common when crews rush the waterproofing before the inspector arrives. In Los Angeles, we see this most on north-facing addition walls where morning dew lingers.
• Shingle granules collecting in gutters after the first Santa Ana wind season. Premature granule loss on a Tamko roof under ten years usually means the shingles were stored flat in sun before install, or the attic ventilation in the addition is insufficient for the extended footprint.
• Sagging ridge line on the new roof section. The addition’s rafters may be undersized for the span, or the Tamko shingles were installed over a second layer that added dead load the engineer didn’t account for. We’ve found this on four Echo Park ADUs built during the 2019-2021 rush.
• Daylight visible through the soffit where the addition connects. The frieze board wasn’t sealed or the Tamko drip edge was omitted - in Los Angeles, this becomes an entry point for rodents and moisture alike.
• Interior drywall cracks running diagonally from the addition corner. Differential settlement between the original foundation and the addition’s new footing, often because the geotechnical report assumed uniform soil that wasn’t uniform. The Tamko roof may be fine; the structure beneath it is moving.

Before

After

Replacement Cost & What’s Included

What drives the range: foundation type (slab-on-grade versus raised), whether the existing sewer lateral can handle the additional fixture count, and how much of the original structure needs opening up. Every quote we write in Los Angeles includes permit fees, LADBS plan check, and a documented photo record - not an upgrade, standard. Under Clause 1 of the Haven Standard, the price is written before anyone starts. No change proceeds without a signed change order, which is why our projects finish within a few percent of the number the customer agreed to.

DIY or Call Us?

There’s plenty a Los Angeles homeowner can check safely: confirm water stains are active (not old) by photographing them after rain, verify your permit status on the LADBS online portal, and measure the addition’s square footage against what was permitted - discrepancies are more common than you’d think. But the actual structural and waterproofing work is not DIY-appropriate. The tie-in between existing and new construction is a load-transfer and waterproofing joint that requires understanding of shear walls, hold-downs, and stepped flashing - get any of it wrong and you’re looking at six-figure remediation, not a weekend project.

We’re an independent contractor, not affiliated with Tamko. If you’re seeing symptoms, call (213) 652-7670 and we’ll schedule a free estimate with a written scope and line-item pricing.

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