A 20×20 addition (400 square feet) costs $100,000–$160,000 in Studio City as a finished habitable room on a flat lot — about $250–$400 per square foot, which is APLA’s own 2026 build rate for a mid-range San Fernando Valley addition. Built out as a full family room or primary suite, with a bathroom, its own HVAC zone and upgraded finishes, the same 400 square feet runs $160,000–$305,000 — at this size scope moves the number far more than the footprint does.
A 12×12 room addition (144 square feet) costs $75,000–$115,000, or roughly $520–$800 per square foot. Small additions cost much more per square foot than large ones, because a 12×12 and a 20×20 both need their own foundation, roof tie-in, permit set and utility runs, and none of those fixed costs shrink just because the floor plan does.
APLA Construction (CA Lic #1136359) builds room additions throughout Studio City, manages the LADBS permit package, and carries all trades under one contract. Studio City’s housing stock is mostly 1950s–1970s ranch homes that are undersized against current values of $1.5M–$4M+, which is why adding square footage here returns more reliably than almost any other project in the Valley.
Most published “cost per square foot” figures assume a normal-sized addition. Applied to a small footprint they understate the real number, often badly. Here is what each common dimension actually runs in Studio City:
| Addition size | Square feet | Studio City cost (2026) | Effective $/sq ft |
|---|---|---|---|
| 10×10 | 100 sq ft | $58,000–$88,000 | $580–$880 |
| 12×12 | 144 sq ft | $75,000–$115,000 | $520–$800 |
| 14×16 | 224 sq ft | $100,000–$155,000 | $445–$690 |
| 20×20 | 400 sq ft | $100,000–$160,000 (habitable room) $160,000–$305,000 (family room or suite) |
$250–$400 $400–$760 |
The pattern matters more than any single row: the smaller the addition, the more each square foot costs. A 12×12 and a 20×20 both need a permit set, a survey, a foundation crew mobilized to site, a roofline tied into the existing structure, and electrical and HVAC extended from the main house. Those costs are close to identical on both. Spread across 144 square feet instead of 400, they land much harder.
These figures assume a habitable room with no plumbing — a bedroom, office, den or playroom — on a flat lot, with builder-grade to mid-range finishes. Our Studio City room addition cost guide quotes $105,000–$190,000 for a “bedroom only” addition; that figure describes a larger 200–350 sq ft bedroom with a walk-in closet and full finishes, which is why a bare 12×12 sits below it.
Four things routinely push a Studio City 12×12 outside that range, and three of them are specific to this neighborhood:
Converting space you already have — a garage, an attached storage room, an oversized hallway — is the cheapest way to add a room in Studio City: a JADU carved out of the existing interior runs $50,000–$90,000, and a garage conversion starts around $80,000. Building new footprint always costs more, because a new room has to buy its own foundation, roof, exterior walls and permit set before it buys a single square foot of living space.
These routes are not interchangeable. The first two produce an independent, rentable unit with its own kitchen and bathroom; the next two produce a room attached to your house. Compare like with like, or the ranking misleads you:
| Route | What you actually get | Studio City cost |
|---|---|---|
| JADU carved from existing interior space | Rentable unit, capped at 500 sq ft | $50,000–$90,000 |
| Garage conversion | Rentable unit | from $80,000 |
| Bump-out under the existing roofline (10×10) | Room only — no kitchen, no bath | $58,000–$88,000 |
| New footprint on a flat lot (20×20) | Room only | $100,000–$160,000 |
| Detached new build, or anything on a hillside lot | Varies | Highest — see below |
Read that table carefully. A 10×10 bump-out at $58,000–$88,000 undercuts a garage conversion on sticker price, and on sticker price alone it is the cheaper job — but it hands you a bedroom with no kitchen and no bathroom, while the conversion hands you a unit you can rent. The cheapest way to add a room and the cheapest way to add space you can let are two different questions with two different answers. Ours compares them side by side in ADU vs room addition in Los Angeles.
Two cases where we would tell you not to take it. First, the garage you are converting may be the only covered parking on a street without permit parking — converting it solves one problem and creates another that surfaces at resale. Second, if what you actually need is a fourth bedroom inside the house, a converted garage or a detached JADU does not read as a bedroom to a buyer or to an appraiser, and on a Studio City ranch the bedroom count is what moves the valuation. The cheapest project that does not do the thing you needed is not cheap.
400 square feet is the point where a room addition stops being a bump-out and becomes a small building. That is why the range is wide. Four things decide which end of it you land on, and only one of them is the size.
What puts a 20×20 at $100,000–$160,000: a flat lot south of Ventura Blvd, a single-story extension off the rear of the house, no plumbing in the new room, builder-grade to mid-range finishes, existing HVAC and electrical service that can carry the extra load, and a roofline the new structure ties into without reframing the existing one.
What pushes it to $160,000–$305,000 or past it: a bathroom (roughly $25,000–$45,000 on its own, and more when the sewer tie-in means cutting a 1950s slab), a second HVAC zone, a service upgrade, wide sliders across the rear elevation, and any hillside work at all.
This is the comparison national cost guides skip, and at exactly 400 square feet it is the one that decides the project. A 400 sq ft detached ADU in Los Angeles costs $140,000–$280,000 — see our Los Angeles ADU cost guide. So the 20×20 addition is normally the cheaper build, but the two are close enough that the right decision is made on the differences that are not price:
Put plainly: if you want a bigger house, build the 20×20. If you want a bigger house and a rent check, price the ADU alongside it first — the gap is smaller than most Studio City homeowners assume.
A single-story addition of this size runs 4–12 weeks on site, and 8–16 weeks in total from contract to completion. LADBS plan check is additional and comes before any of that, at 5–9 weeks. Adding new square footage rather than reworking space you already have adds roughly 1–2 weeks over a comparable interior remodel.
Yes. Studio City is affluent on every standard measure: median household income in ZIP 91604 was $141,875 in 2024, against $81,939 for the City of Los Angeles as a whole, and Zillow put the typical Studio City home value at roughly $1.50 million as of July 2026. Redfin recorded a median sale price of $1,810,000 that same month, up about 12% year over year, at a median of $802 per square foot — comfortably upper-tier for Los Angeles, though not in the band occupied by Hidden Hills, Bel Air or Pacific Palisades, where median household incomes run from roughly $184,000 to over $250,000.
Local wealth is not trivia when you are deciding whether to build. It sets the one ratio that determines whether an addition is an investment or an expense, and in Studio City that ratio is unusually favorable:
Applied to the 20×20 on this page: 400 new square feet cost $100,000–$160,000 to build, while 400 square feet at the local median rate is on the order of $320,000 of house. That gap is the whole reason additions get built in Studio City, and it is why the same 400 square feet in a neighborhood reselling at $400 per square foot is break-even at best. For how that plays out by project type, see our Los Angeles home renovation ROI guide.
Four caveats, and the first two are where homeowners here actually lose money:
One thing high local values do not do is loosen the real constraint. At these prices the 30% renovation rule never binds in Studio City (see the FAQ below); lot coverage, side-yard setbacks and HCRA review are what actually cap an addition here.
Studio City is within the City of Los Angeles. All permits go through LADBS. Standard plan check for room additions: 5–9 weeks. APLA prepares permit packages and coordinates LADBS inspection scheduling throughout the project.
A 12×12 room addition costs $75,000–$115,000 in Studio City, or about $520–$800 per square foot. That is higher per square foot than a larger addition because the permit set, foundation mobilization, roof tie-in and utility runs cost nearly the same on 144 square feet as they do on 400. Adding a bathroom adds roughly $25,000–$45,000, and a hillside lot north of Ventura Blvd can push the total past a flat-lot 20×20.
A 10×10 addition (100 square feet) costs $58,000–$88,000 in Studio City. It is the least efficient way to buy square footage — at $580–$880 per square foot the fixed costs dominate almost completely. If the goal is usable space rather than a specific footprint, going to 12×12 or 14×16 adds far more room than it adds cost.
A 20×20 addition (400 square feet) costs $100,000–$160,000 in Studio City as a finished habitable room on a flat lot — about $250–$400 per square foot, APLA’s 2026 rate for a mid-range San Fernando Valley addition. Built out as a family room or primary suite with a bathroom and full finishes, the same footprint runs $160,000–$305,000. The bathroom alone accounts for roughly $25,000–$45,000, and a hillside lot north of Ventura Blvd can take it past the top of that range. At this size it is worth pricing a 400 sq ft detached ADU ($140,000–$280,000) alongside the addition, because the ADU is rentable and gets a ministerial 60-day approval where the addition needs a 5–9 week LADBS plan check.
In Studio City a room addition costs $250–$400 per square foot for a habitable room on a flat lot with mid-range finishes, which puts a 400 sq ft addition at $100,000–$160,000. Smaller additions cost more per square foot, not less: a 10×10 runs $58,000–$88,000, or $580–$880 per square foot, because the permit set, the survey, foundation mobilization and the roof tie-in cost nearly the same whatever the floor area. The three things that move a quote most are not size at all — whether the new room has plumbing, whether the lot is hillside, and whether the existing panel and HVAC can carry it.
Converting space you already have, rather than building new footprint. In Studio City a JADU carved from existing interior space runs $50,000–$90,000, and a garage conversion starts around $80,000 — the slab, walls and roof already exist. If you want a plain room rather than a rentable unit, a bump-out that stays under the existing roofline is cheapest: a 10×10 runs $58,000–$88,000. Keeping the new space free of plumbing is the single biggest saving available, since a bathroom adds roughly $25,000–$45,000 on its own. The most expensive choices are a detached structure, anything on a hillside lot north of Ventura Blvd, and anything that moves a kitchen or bathroom.
It is the rule of thumb that you should not spend more than 30% of your home’s value on a single renovation. In Studio City it almost never binds. At local values of $1.5M–$4M+, 30% is $450,000–$1.2M, which is well above what any of the additions on this page cost. The real constraints here are lot coverage, setbacks and HCRA hillside review — not the budget ceiling that rule describes.
A ground-floor primary suite addition costs $180,000–$350,000. A family room addition costs $160,000–$305,000. A second story addition costs $375,000–$700,000+. Studio City addition costs are comparable to Sherman Oaks and slightly higher than Encino, reflecting the Studio City address premium and proximity to the eastside/Hollywood.
Yes. Median household income in ZIP 91604 was $141,875 in 2024 against $81,939 citywide for Los Angeles, and the typical home value was about $1.50 million in July 2026 (Zillow), with a median sale price of $1,810,000 at $802 per square foot (Redfin). It is solidly affluent without being top-tier — Hidden Hills, Bel Air and Pacific Palisades all sit well above it. The practical consequence for anyone planning an addition is that finished square footage resells for roughly two to three times what it costs to build, which is why additions are so common here.
By median household income, Hidden Hills is the highest in Los Angeles County at over $250,000, with Pacific Palisades (about $205,600) and Bel Air (about $184,000) next. Studio City, at $141,875, sits below that top tier but well above the $81,939 Los Angeles city median. The difference is visible in build cost: APLA prices additions in Studio City and the wider San Fernando Valley at $250–$400 per square foot, while Beverly Hills, Bel Air, Malibu and the Palisades run $300–$550 per square foot for comparable scope, reflecting finish expectations, site access and hillside conditions.
A ground-floor addition takes 12–20 weeks. A second story takes 16–28 weeks. LADBS plan check (5–9 weeks) is the primary pre-construction timeline driver. APLA begins permit preparation during the design phase to compress total project timeline.
Yes, with additional LADBS review. The Hillside Construction Regulations Area (HCRA) applies to most lots north of Ventura Blvd in Studio City. HCRA review adds time but does not prevent additions from being approved. APLA coordinates HCRA compliance for all hillside Studio City projects.
A primary suite addition on a Studio City ranch home typically returns 90–115% of cost at resale. Converting a 3-bedroom home to 4 bedrooms with a dedicated primary suite is highly valued by buyers at the $1.5M–$4M Studio City price point. Second story additions that bring total square footage to 3,000+ sq ft also deliver strong returns.
Call: (818) 818-4419
Email: info@aplaconstruction.com
CA General Contractor License #1136359 — verify on CSLB
APLA builds additions outside Los Angeles County too: see room additions in Ventura County and room additions in Orange County.
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