The 7 Issues That Cause Most ADUs to Fail Inspection

Why it matters:

Minimum ceiling height is required for a space to be considered habitable.

Typical standard:

• Minimum 7 feet ceiling height (IRC R305)

Common problems:

• Garage conversions with low ceilings

• Raised flooring for plumbing reducing height

• Dropped ceilings for ductwork

What happens if it fails:

The space may not be considered legal living area, requiring costly structural changes.

Why it matters:

Every sleeping area must provide a safe way to exit in case of emergency.

Typical standard:

• Minimum 5.7 sq ft opening (IRC R310)

• Minimum 24” height / 20” width

Common problems:

• Windows too small

• Windows installed too high from the floor

• Non-operable or blocked windows

What happens if it fails:

The room cannot legally be classified as a bedroom.

Why it matters:

Electrical systems must meet safety standards to prevent fire and shock hazards.

Typical requirements:

• GFCI protection in kitchens and bathrooms (NEC 210.8)

• Proper grounding and bonding

• Correct circuit capacity

Common problems:

• Missing GFCI outlets

• Improper wiring or extensions

• Overloaded circuits

What happens if it fails:

The unit may be flagged as unsafe and require electrical upgrades.

Why it matters:

Moisture buildup can lead to mold, damage, and unhealthy living conditions.

Typical standard:

• Mechanical ventilation required if no window (IRC R303.3)

Common problems:

• No exhaust fan

• Fan not vented to exterior

• Undersized ventilation systems

What happens if it fails:

The bathroom may not meet minimum habitability standards.

Why it matters:

Kitchens must meet electrical, ventilation, and safety requirements.

Typical requirements:

• GFCI outlets near sink (NEC 210.8)

• Proper ventilation for cooking

• Adequate spacing and clearances

Common problems:

• Missing GFCI protection

• No range hood or ventilation

• Improper outlet placement

What happens if it fails:

The kitchen may not be approved as a legal cooking space.

Why it matters:

Fire-rated construction helps prevent fire from spreading between units.

Typical requirements:

• Fire-rated walls or ceilings between units (IRC R302)

• Fire-rated doors in some configurations

Common problems:

• Garage conversions without proper drywall

• Shared walls without fire protection

• Missing fire-rated assemblies

What happens if it fails:

The ADU may not be approved due to safety concerns.

Why it matters:

Work must meet code and be properly installed for safety and function.

Typical concerns:

• Improper sewer connections

• Incorrect pipe sizing or slope

• Non-compliant electrical installations

Common problems:

• DIY or contractor work done without permits

• Hidden issues behind walls

• Improper connections to main systems

What happens if it fails:

You may be required to open walls or redo major systems.