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CGI Home Additions & ADU: The Los Angeles Owner’s Guide
CGI home additions and ADU construction in Los Angeles typically runs $53,100 to $153,400 installed, depending on square footage, foundation work, and whether you’re building up or out. We carry and install CGI-compatible structural components, framing packages, and finish materials used across Los Angeles room additions and accessory dwelling units. Most homeowners call us after noticing visible settling, cracked drywall at the new-to-old wall junction, or water staining where the addition ties into the original roofline.
Isaac Pruett spent years watching how Los Angeles additions fail at the seams; the tie-in points, the roofline transitions, the foundation joints. That’s where the money goes, and that’s where the cheap bids hide. If your CGI home addition or ADU is showing stress at those connection points, you’re not imagining it, and you’re not alone.
Key Takeaways:
- Installed costs for Los Angeles home additions using CGI-compatible materials: $53,100 – $153,400
- ADU construction runs $106,200 – $259,600, with garage conversions at $35,400 – $94,400
- We deliver a written price before any work starts, every time
- Every crew member arrives with a photo ID badge and is introduced by name before the visit
- Our work carries the 365-Day Done Right Promise on general contracting and whole-home remodels
Which CGI Models This Applies To
CGI home additions and ADU components in Los Angeles tend to split into two camps: load-bearing structural framing packages and non-structural finish systems. The structural side includes engineered lumber, floor trusses, and roof members sized for California seismic and wind loads. The finish side covers siding, trim profiles, and interior panel systems that align with CGI’s residential series lines.
Before you buy anything, check the stamp on the existing components. CGI products carry a manufacturer’s mark on the edge or end grain of structural members; finish materials usually have a printed label on the back side or on the original packaging. Measure the actual dimensions, not just the nominal size. A 2×6 that’s actually 1.5 inches by 5.5 inches versus one milled at 1.75 by 5.75 matters at the joint. In Los Angeles, we see a lot of owners order by habit (“it’s a standard 2×6, right?”) and end up with a mismatch at the load point. Don’t guess, measure.
On the OEM versus aftermarket question: for structural CGI components, use OEM or a documented equivalent with matching span and load ratings. For non-structural trim and paneling, quality aftermarket pieces from brands we work with like KraftMaid, Cambria, and Silestone often cost less and hold up just as well in our dry Los Angeles climate. We’re an independent service provider, not affiliated with CGI, so our recommendation comes from what we see hold up on actual Los Angeles jobsites, not from a manufacturer’s catalog.
Styles & brands we work with
Signs Your CGI Home Additions & ADU Is Failing
Home additions and ADUs fail predictably in Los Angeles, and the signs usually show up at the seam between old and new construction. Here’s what we see on service calls across the city:
- Diagonal cracks at interior corners where the addition meets the original house. This usually means differential settling; the new foundation is moving at a different rate than the original slab, which is common in Los Angeles’s expansive and shifting soils.
- Gapping between the addition’s roofline and the original roof, especially after a rainy season. Water gets into the gap, swells the framing, and worsens the separation. Left alone, this turns into a full roof tie-in failure within a few seasons.
- Doors and windows in the addition binding or sticking in their frames. That’s the framing racking out of square, typically from moisture cycling or soil movement under the footings. It’s not a paint problem, it’s a structural one.
- Visible water staining along the base of the addition or ADU’s exterior walls. This indicates failed flashing or improper elevation at the foundation. In Los Angeles, even our limited rain events cause major damage when water has a path.
- Squeaking or bouncing floors in the new section while the original floors stay solid. This points to undersized or improperly spaced floor joists or a failed connection at the ledger board.
Any one of these deserves a close look before you pour more money into cosmetic fixes. The underlying issue rarely fixes itself.
Replacement Cost & What’s Included
A full CGI home addition in Los Angeles sits between $53,100 and $153,400, with ADU construction running $106,200 to $259,600 and garage conversions at $35,400 to $94,400. The range comes down to square footage, how much foundation work the soil requires, whether we’re cutting into the existing roof or tying in below the eave line, and what level of finish you choose.
When we price a home additions & ADU project in Los Angeles, the written quote includes all structural components, tie-in hardware, flashing and weatherproofing at the junction, rough and finish carpentry, and the labor to get it done. No verbal estimate that grows on the final bill; what’s on the page is what you pay. Every project ships with our 365-Day Done Right Promise: if the work isn’t right within a year of completion, we make it right at no cost to you. That’s 365 days from the completion date, stated plainly on your written guarantee.
See the difference
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AfterDIY or Call Us?
What you can safely do yourself: inspect the visible joints, flashing, and foundation edges for cracks and water intrusion. Take photos. Watch how water moves around the addition during the next rain. Read your original plans, if you have them, and compare what’s on paper to what’s built. That’s it.
What you shouldn’t do: remove any structural component, open up a load-bearing wall, adjust foundation supports, or cut into your existing roof. This is not a patch-and-paint situation. Framing and foundation work on Los Angeles additions involves concentrated loads, and a failure while you’re working on it can be catastrophic. Even licensed contractors get hurt on tie-in work; this is not a setup for a casual weekend project. If you see signs of structural movement, call (213) 632-5711 and we’ll send someone who will show you exactly who’s coming, with a name and photo before the visit. Know who’s coming, know what it costs, know it’s guaranteed, everything else is just noise.
FAQs
A properly built CGI home addition or ADU in Los Angeles should last 50 to 80 years for the structural shell, assuming the foundation was engineered for local soil conditions and the tie-in points are maintained. The finish surfaces will need replacement periodically; siding, trim, and flashing on the sunny side of your house degrade faster in Los Angeles because the UV and heat cycle are relentless. The structure itself won’t go anywhere if the foundation is right. Call (213) 632-5711 for a free estimate if you’re questioning yours.
Most failing home additions and ADUs in Los Angeles can absolutely be repaired rather than replaced, provided the foundation is still sound and the framing hasn’t suffered extensive water damage. We typically repair tie-in points, re-flash the roofline junction, re-square the framing, and redo the interior finish at the seams. A full replacement is usually only needed when the foundation is compromised or the lumber has rotted through. Call (213) 632-5711 and we’ll tell you which path your project needs.
A tie-in repair or structural correction on a CGI home addition in Los Angeles typically takes one to three weeks, depending on the scope and whether the foundation is involved. A full addition or ADU build takes four to ten months from excavation to finish. You’ll get a written timeline in your written quote before any work starts, and we’d rather quote longer and finish sooner than the other way around. Call (213) 632-5711 for an accurate timeline on your specific project.
We don’t stock every CGI component on a shelf, but we do maintain steady supply relationships with lumber yards and structural fabricators across Los Angeles County, which means your framing and tie-in hardware can be on site within days, not weeks. For non-structural finish pieces, we work with specification-grade partners including KraftMaid, Cambria, and Silestone to match existing surfaces. Call (213) 632-5711 and we’ll confirm availability for your specific component before you commit to anything.
Ready to Fix Your Home Addition or ADU?
You don’t have to live with a cracking addition, a leaking tie-in, or a floor that bounces when you walk across it. We’ll send a background-checked, uniformed technician with a photo ID badge, and you’ll have their name and photo before they arrive. You’ll get a written price before any work starts, with a written guarantee on the back end. Call (213) 632-5711 for your free estimate, and let’s get your home addition or ADU back to doing what it’s supposed to do.
Written by Isaac Pruett, Owner, Mason Remodeling Co at Mason Remodeling Co Los Angeles, serving Los Angeles and nearby areas.
