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 fully permitted and built to code, and the work is scheduled in phases rather than completed same day. Most homeowners reach out after their existing space stops working for them, or after a previous contractor left the rough-in incomplete and the job stalled. You’ll know it’s time when the addition feels like it’s fighting the original roofline, when the tying-in points between old framing and new framing show gaps or water staining, or when the project never passed final inspection. We stock the framing hardware, weatherproofing, and Tamko-compatible roofing and underlayment materials needed to get these jobs moving again, and we write the price before the first tool comes out.

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Which Tamko Systems This Applies To

Tamko is known in California for residential roofing products, waterproof underlayments, and moisture barriers, and those materials show up regularly in the home additions and ADU work we take over in Los Angeles. When an addition ties into an existing roof structure, the Tamko product in play is usually an underlayment or peel-and-stick membrane, and matching the right product matters. The compatibility gotcha: Tamko’s Awaplan and TwinFlex lines have different minimum slope requirements, and if you’re tying a low-slope ADU roof into a steeper main-house roof, the seam at the transition is where leaks start. Check the roll label on any leftover material at the site, or check the permit file if you have it. We measure before we quote. For the roof deck and the transition membrane, OEM Tamko material is worth the cost on ADUs because the manufacturer warranty only works with matched components. For the framing hardware and strapping, quality aftermarket equivalents from Simpson Strong-Tie work just as well and often exceed code minimums in Los Angeles seismic zones.

Signs Your Tamko Home Addition or ADU Is Failing

• Water staining at the tie-in point between the old roof and the new addition. The seam where the new roof plane meets the existing house is the single most common point of failure in Los Angeles, especially after winter rains. If the underlayment was lapped wrong at the transition, water gets driven under the shingles and into the framing.
• Gaps opening between original framing and addition framing. Los Angeles soil expands and contracts with the seasons, and additions built on separate foundations move independently of the main house. A gap at the wall or ceiling junction means the foundation for the addition was not engineered for the soil conditions.
• Musty odor in the new space after rain. The vapor barrier or moisture membrane is not doing its job. In an ADU built over a crawlspace, this usually means the ground-moisture barrier was skipped or installed incorrectly.
• Doors and windows in the addition sticking or out of square. When the addition’s framing settles faster than the rest of the structure, the door and window openings distort. This is not a hardware problem. It is a framing problem, and it does not fix itself.
• Roof deck felt visible at the eaves of the addition. Tamko underlayment exposed at the eaves was not trimmed and flashed correctly at the install. Sun and rain break it down quickly in Los Angeles, and the exposed edge becomes the starting point for bigger roof damage.

Replacement Cost & What’s Included

A home addition in Los Angeles runs $53,100 to $153,400, and an ADU runs $106,200 to $259,600. That range covers the framing correction, the tie-in repair, the Tamko-compatible roofing and moisture barrier work, and the finish work required to make the addition right. Where a repair stays on the smaller end: the framing is sound, the roof deck is intact, and the only issue is the transition membrane. Where the cost climbs: the addition’s foundation was undersized, the original framing at the tie-in needs to be rebuilt, or the city of Los Angeles requires new structural engineering before we can pull the permit. You get a written, line-item price before any work starts, and that number does not move unless the scope changes in writing. Every completed project carries the 365-Day Done Right Promise, which means if the work fails within a full year of completion, we come back and correct it at no charge.

DIY or Call Us?

You can check the visible seams at the roof tie-in, look for water staining along the junction between old and new framing, and pull the permit file from the city of Los Angeles to see what was originally approved. You should not attempt to re-frame a tie-in, re-flash a roof transition, or re-engineer a foundation connection yourself. The framing at the point where an addition meets the existing house carries real structural load, and mistakes there are expensive and dangerous. Curtis Lane has been framing and finishing work across the Los Angeles Basin for the better part of two decades, and the sequencing on these jobs, the order of demo, dry-in, and finish, is where most projects go sideways. If you have a Tamko addition or ADU that is not holding up, call (903) 568-7222 for a straight assessment and a written price.