Simi Valley, Ventura County

Room Addition Cost in Simi Valley, CA

Simi Valley remodeling costs are nearthe California state average. Here's what a typical room addition costs in Simi Valley in 2026, based on a 300 sqf project.

Budget
$57,000
$190/sqf
Mid-Range
$99,750
$333/sqf
High-End
$156,750
$523/sqf

Cost breakdown

Foundation & Framing
30%$29,925
Roofing & Exterior
15%$14,963
Mechanical (HVAC, Electrical)
15%$14,963
Interior Finishes
20%$19,950
Windows & Doors
10%$9,975
Permits & Engineering
10%$9,975

Breakdown based on mid-range estimate of $99,750

Typical Timeline
3-6 months
Permits Required

Building permit, structural engineering, possibly zoning approval.

Remodeling in Simi Valley

Suburban Ventura County city with affordable remodeling by Southern California standards. Many 1970s-80s homes being updated. Hot summers drive HVAC and pool demand.

A room addition adds square footage and value to your home. Costs depend on whether it's a simple bump-out, a second story, or a full wing addition with plumbing.

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Other projects in Simi Valley

Kitchen Remodel
$28,500 – $85,500
Bathroom Remodel
$14,250 – $45,600
ADU / Guest House
$118,750 – $285,000
Roof Replacement
$11,875 – $35,625
Exterior Paint
$4,750 – $16,625
Whole House Remodel
$256,500 – $855,000

Room Addition cost in other California cities

San Diego
$60,000 – $165,000 | San Diego County
Pacifica
$72,000 – $198,000 | San Mateo County
Sonoma
$69,000 – $189,750 | Sonoma County
Corte Madera
$72,000 – $198,000 | Marin County
San Mateo
$75,000 – $206,250 | San Mateo County
Tiburon
$81,000 – $222,750 | Marin County
Sausalito
$78,000 – $214,500 | Marin County
Palo Alto
$81,000 – $222,750 | Santa Clara County

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