- Typical cost
- $250 – $500+ per square foot depending on type and complexity
- Typical timeline
- 6–12 months including design and permitting
- Permits through
- City of Calabasas Building & Safety
- Service area
- Calabasas, San Fernando Valley
Types of Additions
We build out, up, and into existing space, whichever makes sense for your lot, your budget, and what the city will approve.
- Single-story rear and side additions
- Second-story additions
- Primary suite and bathroom additions
- Kitchen expansions and bump-outs
- Enclosing patios and converting non-living space
Room Additions & Second Stories Conditions in Calabasas
Beyond the double review, the terrain drives cost here. Many lots are graded hillside pads, which means engineered foundations, retaining walls and real geotechnical work before anything goes vertical. Most of the city also sits in a high fire severity zone, and mature oaks are protected, so both can reshape a footprint during design rather than after.
- City plan check plus HOA architectural review, run in parallel
- Hillside pads that call for caissons, grade beams or retaining walls
- Geotechnical and structural engineering as a normal line item
- Fire-hardened assemblies: ember-resistant vents, rated eaves, non-combustible cladding
- Protected oak trees that set where you can and cannot build
What Drives the Cost
A second story usually costs more per square foot than building out, because the existing foundation and framing often need reinforcement to carry the new load. On a flat lot with room to spare, going out is almost always cheaper than going up.
- Foundation and framing reinforcement
- Roof tie-ins and re-roofing where they meet
- Panel upgrades and HVAC capacity
- Hillside and soils reports where applicable
Design, Engineering and Permits
Additions require structural engineering, Title 24 energy compliance, and full plan check. We coordinate the engineer, submit to LADBS or your city, and handle corrections until the permit is issued.
- Architectural plans and structural engineering
- Setback, FAR and height verification
- Title 24 energy calculations
- Plan check corrections handled by us
FREQUENTLY ASKED QUESTIONS
Do you do room additions & second stories in Calabasas?
Yes. Calabasas is part of our regular service area. We'll come out for a free on-site consultation, walk the property, and tell you what's realistic before you spend anything on design.
What does room additions cost in Calabasas?
$250 – $500+ per square foot depending on type and complexity. Site conditions in Calabasas and your material selections move the number, which is why we price after walking the property rather than over the phone.
Who issues the permit in Calabasas?
Permits for this work go through City of Calabasas Building & Safety. We handle the submittal, plan check corrections and inspections as part of the project.
How much does a room addition cost in Los Angeles?
Expect $250 to $500+ per square foot depending on whether you're building out or up, the finishes, and what structural reinforcement the existing house needs.
Is it cheaper to build out or add a second story?
Building out is usually cheaper if your lot has room, because a second story often requires reinforcing the existing foundation and framing to carry the added load.
How long does a room addition take?
Plan on 6 to 12 months total: design and engineering, plan check at the city, then 3 to 6 months of construction depending on size.
Do you build home additions near me outside the City of Los Angeles?
Yes. We build primary suite additions, second stories and house extensions across a 100-mile radius of Woodland Hills, the San Fernando Valley, Ventura County, the Westside, the South Bay and Orange County. Each city runs its own plan check, and we handle whichever one governs your parcel.
Similar Projects We've Built
Second-Story Addition in Burbank
A 1,050 sq ft second story added over an existing 1940s single-story home, with foundation and framing reinforcement to carry the new load.
Family Room and Bath Addition in Glendale
A vaulted family room and full bathroom added off the rear of a 1958 Glendale home, opening to the backyard with a wide sliding door.
Room Addition on El Rodeo Rd, Rancho Palos Verdes
On El Rodeo Rd in Rancho Palos Verdes, a rear addition added a family room and fourth bedroom to a single-story peninsula home, matched to the existing roofline.
DISCUSS YOUR PROJECT WITH 1 SMART BUILD
Licensed, bonded and insured design-build general contractor serving Los Angeles County and Southern California. Tell us about your property and goals, and we'll walk you through feasibility, permitting and a clear plan.