Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Sterling Home Additions & ADU: The Los Angeles Owner's Guide
When a Sterling home addition or accessory dwelling unit shows signs of wear, settlement, or water intrusion, we handle it. A full Sterling addition or ADU project in Los Angeles typically runs $53,100 to $153,400, with most of that range driven by square footage, foundation work, and whether you're building on a slab or over a crawl space. Owners usually call us after spotting a persistent leak at a tie-in seam, a door that no longer closes square, or drywall cracks running from a corner where the addition meets the original structure. The good news: we diagnose the failed component, price the repair or rebuild in writing, and often complete the fix before it becomes a structural headache.
We stock and install hardware, flashing, sealants, and framing components compatible with Sterling additions and ADUs across Los Angeles. We're an independent Southern California general contractor, not a Sterling dealer or affiliate. What that means for you is simple: we're free to recommend the best available part, whether that's a Sterling-specific match or a higher-grade aftermarket equivalent at a better price.
Which Sterling Models This Applies To
Sterling's residential line spans several construction types, and the failed part on your addition or ADU is usually tied to how the unit was originally framed and sealed, not a single model number stamped on a plate. We work on Sterling additions built with standard 2×4 and 2×6 framing, on raised foundations and slab-on-grade, and on both permitted and unpermitted ADU conversions across Los Angeles.
Here's the compatibility gotcha most homeowners don't learn until a bad inspection: Sterling's older valley and foothill builds from the early 2000s used a narrow 3-5/8-inch metal corner bead and a single-layer WRB (weather-resistant barrier) at the tie-in. That's fine for a dry year. In a Los Angeles winter with sustained rain, it's not. We now spec a 4-inch flexible flashing at every vertical seam and a secondary drainage plane on any tie-in we touch. If you still have the original permit packet, look for the sheet that lists the WRB spec. If it says "15-lb felt, single layer," plan on an upgrade.
For replacement parts like tie-in flashing, sill gaskets, and anchor hardware, we recommend OEM Sterling components where they still exist. Sterling quietly discontinued several older ADU trim profiles around 2019, and chasing those parts is a waste of your time and money. In most cases, a quality aftermarket equivalent from a supplier we trust performs better and costs 15 to 20 percent less.
Styles & brands we work with
Signs Your Sterling Home Additions & ADU Is Failing
- Water staining at the ceiling-to-wall corner where the addition meets the original house. This is almost always a failed kickout flashing or a skipped transition membrane. Water follows the seam, pools, and stains. Left alone, it rots the top plate and invites termites in Los Angeles faster than you'd believe.
- A door that binds at the top or drags at the threshold. That's settlement or, less often, a header that was undersized when the opening was cut. One is fixable with shimming; the other means opening the wall. We can tell which in about ten minutes on site.
- Drywall cracks radiating from a window corner or a beam pocket. In an ADU, this is frequently a missing or undersized king stud or a shear panel that was omitted to save an afternoon. It will not self-heal. It will get wider.
- A musty smell in the addition, stronger near the floor. That's moisture wicking up through a slab that was poured without a proper vapor barrier, or a crawl space without cross-ventilation. Los Angeles clay soil holds water longer than most people think after a wet winter.
- Floor squeaks that you can isolate to one joist bay, or a floor that feels springy. A failed adhesive bond or a joist that has cracked at a knot. Squeaks are annoying. Springy is a warning sign. Both get addressed differently, and both are worth a look before you place furniture over them for another five years.
See the difference
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AfterReplacement Cost & What's Included
For a Sterling home addition or ADU repair in Los Angeles, you're usually looking at one of three scopes. A targeted component fix like a tie-in flashing replacement or a door re-shim runs $470 to $2,125. A more involved repair, like opening a wall to sister a cracked joist or re-flashing a dormer, lands $4,130 to $11,800. A full addition or ADU rebuild, where we're re-framing sections and re-waterproofing the entire connection, carries the $53,100 to $153,400 range we lead with. The spread depends on access, whether asbestos or lead testing is required, and whether your Los Angeles hillside lot triggers additional structural engineering.
Every price we give is written before we start. That written price covers the part, the labor, the disposal, and the permit if one is required. You'll see it itemized, and it won't change unless you change the scope. We wrap every repair with a written guarantee, and if something fails within 365 days of completion, we come back and make it right at no charge. That's the 365-Day Done Right Promise, and it's not a sales line. It's in the paperwork.
DIY or Call Us?
There are a few things you can safely check before calling. You can inspect your exterior caulk lines for gaps, look for daylight under exterior doors, and run a hose along the tie-in seam on a dry day to see where water travels. You should not climb onto an addition roof, open a wall to inspect framing, or try to re-flash a seam yourself. Most tie-in failures involve working at height, off a ladder, on a pitch, with flashing that's sharp. That's how people get hurt. If you can see it from the ground, look. If you can't, call us at (213) 632-5711 and we'll do it properly. Isaac Pruett grew up in the San Fernando Valley and has spent twenty years on Los Angeles roofs and in Los Angeles crawl spaces. He's still got all his fingers. That's not luck.
Know who's coming, know what it costs, know it's guaranteed, everything else is just noise.
FAQs
A properly built addition should deliver 30 to 50 years of structural life, with the tie-in seams and exterior sealants needing attention every 5 to 8 years in Los Angeles sun and smog exposure. UV breaks down sealant faster here than almost anywhere else in the country. Call (213) 632-5711 for an exact assessment; estimates are free.
Most failing additions can be repaired, often by addressing the specific component that failed, whether that's flashing, a joist, or a settling corner. Rebuilds are only necessary when the framing has rotted or the foundation has moved beyond simple correction.
Most single-component repairs take two to three days on site, including dry time and inspection. A full addition rebuild runs longer. We'll give you a written window before we start, and it's one we actually hit.
We stock common tie-in flashing, sill gaskets, anchor hardware, and aftermarket trim profiles for Sterling additions and ADUs on our trucks and at our Los Angeles yard. OEM-only parts that Sterling has discontinued get ordered from vetted distributors, and we'll tell you the lead time before you commit.
Written by Isaac Pruett, Owner, Mason Remodeling Co at Mason Remodeling Co Los Angeles, serving Los Angeles and nearby areas.
