BOSS Three Bed Core | 1,200 Sq Ft 3-Bedroom Prefab ADU (30×40)

BOSS Three Bed Core 1,200 sq ft 3-bedroom prefab ADU — front exterior view in California
BOSS Three Bed Core 30' x 40' prefab ADU — angled exterior with galvanized steel roof
BOSS Three Bed Core 1,200 sq ft accessory dwelling unit — exterior side profile
BOSS Three Bed Core prefab ADU — rear exterior with double-pane black-framed windows
BOSS Three Bed Core 3-bedroom ADU — entry view with modern black aluminum door
BOSS Three Bed Core California backyard ADU — exterior elevation view
BOSS Three Bed Core prefab ADU — exterior view with landscaping
BOSS Three Bed Core 1,200 sq ft ADU — interior open living area with natural light
BOSS Three Bed Core prefab ADU — interior kitchen and cabinetry
BOSS Three Bed Core 3-bedroom ADU — interior dining area
BOSS Three Bed Core 3-bedroom ADU — primary bedroom interior
BOSS Three Bed Core 3-bedroom ADU — second bedroom interior
BOSS Three Bed Core 3-bedroom ADU — third bedroom interior
BOSS Three Bed Core 30' x 40' 3-bedroom ADU — floor plan and dimensions
BOSS Three Bed Core 1,200 sq ft 3-bedroom prefab ADU — front exterior view in California
BOSS Three Bed Core 30' x 40' prefab ADU — angled exterior with galvanized steel roof
BOSS Three Bed Core 1,200 sq ft accessory dwelling unit — exterior side profile
BOSS Three Bed Core prefab ADU — rear exterior with double-pane black-framed windows
BOSS Three Bed Core 3-bedroom ADU — entry view with modern black aluminum door
BOSS Three Bed Core California backyard ADU — exterior elevation view
BOSS Three Bed Core prefab ADU — exterior view with landscaping
BOSS Three Bed Core 1,200 sq ft ADU — interior open living area with natural light
BOSS Three Bed Core prefab ADU — interior kitchen and cabinetry
BOSS Three Bed Core 3-bedroom ADU — interior dining area
BOSS Three Bed Core 3-bedroom ADU — primary bedroom interior
BOSS Three Bed Core 3-bedroom ADU — second bedroom interior
BOSS Three Bed Core 3-bedroom ADU — third bedroom interior
BOSS Three Bed Core 30' x 40' 3-bedroom ADU — floor plan and dimensions
BOSS Three Bed Core 1,200 sq ft 3-bedroom prefab ADU — front exterior view in California
BOSS Three Bed Core 1,200 sq ft 3-bedroom prefab ADU — front exterior view in California BOSS Three Bed Core 30' x 40' prefab ADU — angled exterior with galvanized steel roof BOSS Three Bed Core 1,200 sq ft accessory dwelling unit — exterior side profile BOSS Three Bed Core prefab ADU — rear exterior with double-pane black-framed windows BOSS Three Bed Core 3-bedroom ADU — entry view with modern black aluminum door BOSS Three Bed Core California backyard ADU — exterior elevation view BOSS Three Bed Core prefab ADU — exterior view with landscaping BOSS Three Bed Core 1,200 sq ft ADU — interior open living area with natural light BOSS Three Bed Core prefab ADU — interior kitchen and cabinetry BOSS Three Bed Core 3-bedroom ADU — interior dining area BOSS Three Bed Core 3-bedroom ADU — primary bedroom interior BOSS Three Bed Core 3-bedroom ADU — second bedroom interior BOSS Three Bed Core 3-bedroom ADU — third bedroom interior BOSS Three Bed Core 30' x 40' 3-bedroom ADU — floor plan and dimensions
PRODUCT DESCRIPTION

The BOSS Three Bed Core is a 1,200 sq ft three-bedroom prefab ADU (accessory dwelling unit) built in California by BOSS Homes — a modern, code-ready backyard home ideal as a full-size rental, multigenerational living space, or independent home for family. Its 30’ × 40’ footprint and 11’6” overall height create a spacious three-bedroom layout, while precision-engineered light-gauge steel framing delivers exceptional structural strength and low-maintenance durability. The Three Bed Core ships on standard pallets — no cranes or oversized transport — and most projects move from order to move-in in roughly 4 to 9 months.

Like every BOSS model, the Three Bed Core is engineered to meet both the International Building Code (IBC) and California Building Code (CBC), so it is permittable as a backyard ADU or granny flat across California — including Los Angeles, San Diego, San José, and more. Explore the full prefab ADU guide or browse all 8 BOSS models.

Price does not include installation or permitting.

  • 1,200 sq ft modern three-bedroom backyard ADU — perfect for full-size family living, rental income, or multigenerational housing
  • Spacious 30’ × 40’ footprint with an 11’6” overall height for an open, comfortable layout
  • Precision-engineered light-gauge steel framing for long-lasting structural strength
  • Premium galvanized steel roof in corrugated or standing-seam profiles for superior weather protection
  • Energy-efficient PIR insulation — Roof R-28 and Walls R-42 (4” insulation)
  • Weatherproof interlocking wall panels with steel studs for maximum durability in any climate
  • Fire-safe construction with FM-approved Class 1 materials and self-extinguishing insulation
  • Modern black aluminum windows & doors with double-pane glass
  • Customizable window & door placement tailored to your design preferences
  • Standard interior package included — interior doors & hardware, cabinetry, finish flooring, paint, and electrical & plumbing fixtures
  • Mini-split A/C system included for year-round comfort
  • Meets International & California Building Codes for permitting confidence
  • Eco-friendly materials made with 35% recycled post-consumer content
  • Backed by a 10-year structural warranty
  • Square footage: 1,200 total sq ft
  • Unit footprint: 30’ × 40’
  • Unit height: 11’6”
  • Bedrooms: 3
  • Structure: precision-engineered light-gauge steel framing
  • Roof: painted galvanized steel, corrugated or standing-seam profile
  • Doors & windows: black aluminum frame with double-pane glass; medium window 28″ × 42″, large window 28″ × 64″, entry door 36″ × 80″ (locations customizable)
  • Interior ceiling height: 8’0” – 10’6”
  • Standard interior package: interior doors & hardware, cabinetry, mini-split A/C, electrical & plumbing fixtures, finish flooring, and paint (kitchen appliances excluded)
Sku: 30x40BedCore
In stock! Usually ships within 48 hours.
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$205,195

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