Getting Started with ADU Construction

Pre-Construction Checklist

Documentation

  • Approved building permits
  • Construction drawings
  • Engineering calculations
  • Site survey
  • Utility plans

Site Preparation

  • Property line verification
  • Utility locating
  • Soil testing
  • Tree protection
  • Access planning

Team Assembly

  • General contractor selection
  • Subcontractor coordination
  • Material suppliers
  • Inspection scheduling
  • Project management plan

Construction Methods

Traditional Construction

Traditional Site-Built

Advantages

  • Maximum customization
  • Adaptable to site conditions
  • Local contractor availability
  • Phased construction possible

Timeline

4-8 months typical

Cost Range

$300-400/sq ft

Modular Construction

Modular/Prefabricated

Advantages

  • Faster construction
  • Quality control
  • Weather-independent building
  • Predictable costs

Timeline

2-4 months typical

Cost Range

$250-350/sq ft

Panelized Construction

Panelized Systems

Advantages

  • Reduced on-site time
  • High energy efficiency
  • Structural integrity
  • Design flexibility

Timeline

3-6 months typical

Cost Range

$275-375/sq ft

Materials & Systems

Structural Systems

Wood Frame

  • Most common method
  • Cost-effective
  • Readily available
  • Easy modifications

Steel Frame

  • High strength
  • Fire resistant
  • Pest resistant
  • Long spans possible

SIPs (Structural Insulated Panels)

  • Energy efficient
  • Quick assembly
  • Strong & lightweight
  • Reduced thermal bridging

Foundation Systems

Slab on Grade

  • Cost-effective
  • Quick installation
  • Good for level sites
  • Minimal excavation

Raised Foundation

  • Access to utilities
  • Better for sloped sites
  • Improved ventilation
  • Easier modifications

Pier Foundation

  • Minimal site impact
  • Good for varied terrain
  • Reduced excavation
  • Seismic performance

Finding Qualified Contractors

Contractor Requirements

In California, ADU contractors must meet specific requirements:

  • Valid California Contractor's License (B-General Building)
  • Workers' compensation insurance
  • Liability insurance
  • Local business licenses
  • Bonding requirements

Selection Process

1

Research

  • Check CSLB license status
  • Read online reviews
  • View completed projects
  • Verify insurance
2

Interview

  • ADU experience
  • Local code knowledge
  • Project timeline
  • Communication style
3

Verify

  • Contact references
  • Visit past projects
  • Check complaints
  • Review licenses
4

Compare

  • Detailed bids
  • Scope of work
  • Timeline commitments
  • Payment terms

Red Flags to Watch For

Pricing Issues

  • Unusually low bids
  • Large upfront payments
  • Cash-only deals
  • Pressure tactics

Documentation

  • No written contract
  • Missing licenses
  • No insurance proof
  • Vague proposals

Communication

  • Poor responsiveness
  • Unclear timeline
  • No references
  • Evasive answers

Construction Timeline

Phase 1: Site Preparation

1-2 Weeks

  • Site clearing
  • Utility locating
  • Grading
  • Erosion control

Phase 2: Foundation

2-3 Weeks

  • Excavation
  • Forming
  • Reinforcement
  • Concrete placement

Phase 3: Framing

3-4 Weeks

  • Wall framing
  • Roof framing
  • Sheathing
  • Weather barrier

Phase 4: Systems

3-4 Weeks

  • Electrical
  • Plumbing
  • HVAC
  • Insulation

Phase 5: Finishes

4-6 Weeks

  • Drywall
  • Flooring
  • Cabinets
  • Fixtures

Phase 6: Completion

1-2 Weeks

  • Final inspections
  • Punch list
  • Cleaning
  • Certificate of occupancy

Inspections & Compliance

Required Inspections

Foundation

  • Soil compaction
  • Forms and reinforcement
  • Drainage systems
  • Waterproofing

Framing

  • Wall construction
  • Roof structure
  • Shear walls
  • Hardware installation

Mechanical

  • Electrical rough-in
  • Plumbing rough-in
  • HVAC installation
  • Gas lines

Final

  • Life safety systems
  • Energy compliance
  • Accessibility
  • Site work completion

Ready to Start Your ADU Project?

Let us help you find qualified contractors and guide you through the construction process.