Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
CWS Home Additions & ADU: The Los Angeles Owner’s Guide
A CWS home addition or ADU in Los Angeles typically runs between $53,100 and $153,400 installed, and we finish most additions in 10 to 16 weeks once permits clear. The bigger cost driver is not square footage alone. It’s what’s under the slab and inside the walls: foundation work, panel upgrades, and the Los Angeles Department of Building and Safety plan review all move the number faster than anything in the floor plan.
Most homeowners call us when an existing CWS addition starts showing its age: a door that no longer squares up, a roofline that sags at the tie-in, or a permit issue from the previous build that never got closed out. Isaac Pruett has walked enough of these job sites to know the difference between a cosmetic crack and a structural one, and we price the fix in writing before anyone swings a hammer.
Key Takeaways:
- Installed CWS home addition or ADU work in Los Angeles: $53,100 – $153,400
- Garage conversions run $35,400 – $94,400; full ADU construction runs $106,200 – $259,600
- We are an independent Los Angeles contractor, not affiliated with CWS
- Written price before work starts, every time
- 365-Day Done Right Promise on all work
Which CWS Models This Applies To
CWS built additions across a range of Southern California homes, and the compatibility question almost always comes down to the tie-in point, not a model number. We work on CWS stick-built room additions, attached ADUs, detached ADUs, and garage conversions. If your CWS project involved a laundry-to-living conversion, a rear yard ADU, or a second-story bump-out, our crews have seen the framing and foundation approach those builds used.
Where OEM versus aftermarket matters on CWS work is in the structural connectors and the waterproofing details. CWS additions built in the late 1990s through the 2010s often used standard Simpson Strong-Tie hardware, which we match exactly. But the flashing details at the roof-to-existing-house tie-in varied from job to job. That’s the spot where Los Angeles rain, as infrequent as it is, finds a way in. We spec materials that match what’s already there, not whatever is cheapest at the supply yard. If the addition has stucco, we match the existing texture and repaint with a color-matched finish so the seam disappears.
Styles & brands we work with
Signs Your CWS Home Additions & ADU Is Failing
- Doors that stick or won’t latch. When an addition settles unevenly, the door frames rack out of square. This often traces back to foundation movement or undersized beams at the tie-in.
- Wall cracks at the seam where the addition meets the original house. Some hairline cracks are normal. Cracks wider than 1/8 inch that keep growing point to differential settlement.
- Musty smell or water stains at the roofline. Failed flashing at the tie-in lets water into the framing. In Los Angeles, this shows up after the first real rain following a dry year.
- Floor slope you can feel when you walk. More than a 1/2 inch drop over 10 feet suggests a framing or foundation issue that will not correct itself.
- Electrical flicker when the addition’s AC or heater kicks on. CWS additions sometimes shared circuits with the main house. If the panel is undersized, you get voltage drop and tripped breakers.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
A full CWS home addition or ADU replacement project in Los Angeles runs $53,100 – $153,400. Garage conversions fall between $35,400 – $94,400. A ground-up ADU runs $106,200 – $259,600. The range depends on whether we’re repairing a failed tie-in, redoing a foundation section, or taking the structure down and rebuilding.
What’s included: all framing, drywall, insulation, electrical, plumbing, HVAC tied into the existing systems, finish work, and the written warranty. Every quote lists labor and materials separately, so you see exactly what you’re paying for. We pull permits, schedule inspections, and do not draw a final check until the city signs off. The 365-Day Done Right Promise covers the work from the completion date. A free return visit if something fails within that year is part of our standard terms.
DIY or Call Us?
Here’s the honest split. You can safely check the obvious things: run a level across the floor, note where cracks are and whether they’re growing, and look for water stains at the tie-in. That information helps us quote faster.
What you should not DIY is anything touching structure, electrical, or gas. Cutting into a load-bearing wall without shoring it properly can collapse the roof. Moving circuits on an undersized panel is a fire risk. Gas line work is a licensed-trade job in Los Angeles, full stop. We see the remains of DIY attempts on addition repairs regularly, and they always cost more to undo than the original repair would have. Call (803) 680-2547 and we’ll send a crew lead who can tell you what’s wrong and what it costs to fix.
FAQs
A well-built CWS addition should last 50 to 80 years in Los Angeles with standard maintenance. The weak points are the tie-in flashing and the foundation, which is why we inspect both before quoting any repair. Call (803) 680-2547 and we’ll walk the addition with you free.
That depends on what failed. Flashing, drywall, and framing repairs are usually straightforward. Foundation settlement often means helical piers or slab work, which is costlier. We’ll give you a written repair option and a replacement option side by side, so you decide with real numbers in front of you.
Typical repairs run 2 to 6 weeks depending on scope. A full addition or ADU build runs 10 to 16 weeks once Los Angeles permits clear. We’ll put the schedule in the written quote, including permit and inspection dates, so you know when your house is quiet again.
We stock the common structural connectors, flashing materials, and finish components for CWS additions on our trucks. For specialty items, we order through our supplier network, including KraftMaid, Cambria, and Silestone when the job calls for finishing touches. Call (803) 680-2547 and we’ll tell you if we have what your job needs before scheduling.
If your CWS addition or ADU in Los Angeles is showing its age, call Mason Remodeling at (803) 680-2547. We’ll schedule a free estimate, put the price in writing, and introduce you to the crew lead by name and photo before anyone shows up at your door. Written price before work starts, 365-Day Done Right Promise, and a live person on the phone when you call. Know who’s coming, know what it costs, know it’s backed up – everything else is just noise.
Written by Isaac Pruett, Owner, Mason Remodeling at Mason Remodeling, serving Los Angeles and nearby areas.
