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Tamko Home Additions & ADU: The Orange County Owner’s Guide
A full Tamko home addition or ADU in Orange County typically runs $45,000 to $130,000 installed, with ADU construction landing between $90,000 and $220,000 depending on square footage, site conditions, and finish level. We match existing Tamko rooflines, siding lines, and trim profiles so the addition reads as original construction, not a bolt-on. Most homeowners call us after a previous contractor’s number changed once the walls were open, or after realizing the new roofline doesn’t tie into the existing Tamko shingle coursing the way it should.
You’re not just buying framing and drywall. You’re buying a seamless extension of a house that already has a Tamko envelope, and the wrong approach on flashing, venting, or coursing means water where it shouldn’t be inside of two rainy seasons. Trevor Nash and our crew have been working throughout Orange County for years, including projects in Irvine’s older neighborhoods near the Spectrum where 1980s and 90s builds get second stories, bump-outs, and garage conversions tied into existing Tamko roof systems.
Which Tamko Models This Applies To
Tamko’s residential line spans Heritage, Elite Glass-Seal, and Titan XT architectural shingles, plus the metal and composite trim accessories that finish them. The compatibility question that trips up most additions is the roofing layer: if your existing home carries a discontinued Tamko color lot or a shingle profile that’s no longer manufactured, the new roof section needs a deliberate match or a planned transition. We pull a physical sample off the existing slope and match the coursing, exposure, and color under daylight before we order a single bundle.
On the OEM-versus-aftermarket decision for Tamko roofing on additions: Tamko does not license aftermarket shingle manufacturers. A generic architectural shingle with a similar profile is not the same product, and mixing brands on a single roof plane voids the warranty coverage on the Tamko side. For siding and trim components, we source Tamko-compatible flashing, underlayment, and edge details from supply houses in Orange County and verify substrate condition before we tie in. The coursing, exposure, and nailing pattern all have to match the original slope, or the patch reads from the street and leaks at the transition.
Styles & brands we work with
Signs Your Tamko Home Addition or ADU Is Failing
- Water staining around the addition’s wall-to-roof junction: The flashing was lapped backward or the step flashing doesn’t extend far enough up the slope. We see this on a lot of Orange County additions where the roofline was tied in by a framing crew that never pulled a shingle course properly.
- Visible seam or color break where new roof meets old: The addition’s roofline wasn’t coursed into the original Tamko exposure, so the rows don’t align. It leaks faster than it looks bad, and it looks bad immediately.
- Drywall cracks running from the new wall into the original ceiling plane: The addition’s rafters were bearing on a point load the original plate wasn’t built for. This is a structural tie-in problem, not a caulk fix.
- Moisture or efflorescence on the interior wall of the ADU after rain: The underlayment wasn’t lapped correctly onto the existing wall plane, so wind-driven rain pushes up under the laps in Orange County’s winter storms.
- Roof deck feels soft or sounds different when walked near the transition: The original Tamko decking rotted at the tie-in because the old flashing was never replaced when the new slope was added. By the time it feels soft, the rot has been working for a season or two.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
In Orange County, a Tamko home addition runs $45,000 to $130,000, and an ADU runs $90,000 to $220,000. What moves the number: square footage, whether you need a new foundation versus tying into the existing slab, how much of the original Tamko roof slope has to be removed and re-flashed, and whether the project needs engineered plans and city sign-off. A garage conversion runs $30,000 to $80,000 because the envelope is already there; a second-story bump-out hits the top of the range because you’re lifting the roofline off half the house first.
Every project gets a written price before we pull a permit or swing a hammer. The number on day one is the number on the invoice. That’s the Kingswell standard: say the price before the work, show up in the window we gave, leave the site cleaner than we found it. And the 365-Day Done Right Promise covers the tie-in, flashing, and any part of the addition that fails inside the guarantee period. If something isn’t right, we come back and fix it at no charge. In writing, every time.
| Project | Orange County Installed Range |
|---|---|
| Home addition | $45,000 – $130,000 |
| ADU construction | $90,000 – $220,000 |
| Garage conversion | $30,000 – $80,000 |
DIY or Call Us?
What you can safely check on your own: whether the new roof courses line up with the old ones, whether flashing laps face downhill and not uphill, and whether water is pooling anywhere near the transition. Those are observation jobs. You can also pull out the paperwork from the original addition and check whether the Tamko warranty registration was ever filed, because if it wasn’t, no repair is covered.
What you should not do is pull shingle courses, cut into the existing roof deck, or attempt a flashing repair on a two-story transition. Working on a sloped roof with a fall height over six feet is how experienced carpenters end up in urgent care. And a bad flashing repair on a Ramko tie-in means water inside the wall cavity where you won’t see it until the drywall mushrooms. If the transition is leaking, call us at (424) 541-1701. We’ll put a number on the repair in writing before anything gets opened up.
FAQs
A properly flashed and coursed Tamko tie-in on an Orange County addition lasts as long as the original roof system, typically 20 to 30 years depending on sun exposure and storm direction. The weak point is always the flashing transition, not the shingle itself. Call (424) 541-1701 for an exact assessment of your existing tie-in; estimates are free.
If the flashing is the failure point and the decking underneath is still solid, the repair is usually a one-day re-flash and re-course of the affected section. If the decking has rotted or the structural tie-in is undersized, the repair scope grows. We’ll tell you which one you’re looking at before we quote, and the quote is in writing.
A garage conversion usually runs 8 to 12 weeks from permit to punch list. A full ADU runs 4 to 7 months depending on foundation work and utility trenching. A second-story addition runs 5 to 8 months. We give you a written schedule before we start, and we hold to it the way we hold to the price.
We stock a working supply of common Tamko Heritage and Titan XT colors, standard step flashing, underlayment, and edge trim on our service vehicles. Discontinued colors get ordered from our Orange County supply houses with a physical sample match before installation. We also work with KraftMaid and Cambria cabinetry and Silestone countertops when the addition includes a kitchen or bath.
Written by Trevor Nash, Owner, Penhallow Remodeling Orange County at Penhallow Remodeling Orange County, serving Orange County and nearby areas.
