Cost and planning guide

Garage Conversion Plans for ADUs

Garage conversion plans need to prove that an old utility/storage structure can become legal living space. That means code, structure, utilities, fire/life safety, energy, and habitability.

Reviewed 2026-05-15

Guide

What homeowners need to know.

Draw the existing condition first

A good plan starts by documenting what is actually there: slab, framing, roof, openings, utilities, drainage, and access.

Show the legal conversion path

Plans should answer fire separation, insulation, egress, bathroom/kitchen layout, utility routing, and energy requirements.

Use feasibility before finishes

A beautiful cabinet layout means nothing if the slab, ceiling height, or fire wall does not work.

Cost table

Use ranges until scope is real.

Item Planning range Why it moves
Feasibility review $1k-$5k+ Useful before committing to full drawings.
Permit plans $10k-$35k+ Depends on structure, engineering, and city comments.
Construction $120k-$300k+ Existing condition drives the spread.

Mistakes

Avoid these expensive shortcuts.

  • Designing finishes before verifying legal conversion blockers.
  • Forgetting moisture, insulation, and fire separation.
  • Not checking utilities until after layout.

FAQ

Fast answers.

What should garage conversion plans include?

They should include existing conditions, proposed layout, fire/life safety, structure, energy, utilities, and city-specific submittal items.

Sources

Official and provider sources checked.

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