What Makes a Garage Conversion Expensive?

Two identical-looking garages. One converts for $105K, the other for $175K. The difference is always hiding in one of six places.

1. Old foundations and missing footings. The champion cost driver, met in Module 2. Garages built decades ago often sit on a 3–4 inch floating slab with no perimeter footings. A dwelling needs a foundation rated for living loads — retrofitting footings under existing walls means cutting, excavating, and pouring in sections. Cost impact: $15K–$50K+ depending on how much is missing.

2. Structural retrofit. Removing the garage door means a new wall — often a shear wall doing seismic work. Old framing may need sistering, new hold-downs, or reinforcement to meet current earthquake code. Cost impact: $8K–$25K.

3. Utilities. Three separate questions: Is the electrical panel big enough or does it need an upgrade ($5K–$15K+)? How far must sewer and water travel from the garage to existing lines ($5K–$20K+ depending on distance and what's in the way)? Does the gas situation force decisions (many conversions go all-electric to skip gas entirely)?

4. The roof. A roof at end-of-life gets replaced during conversion — nobody insulates and drywalls under a roof about to leak. New roof: $8K–$20K. Also: garages with 2x4 rafters may need structural work just to carry required insulation and drywall weight.

5. Framing surprises. Termites, dry rot, and DIY modifications from previous owners reveal themselves at demolition. Sound framing costs nothing; replacing half of it costs plenty.

6. Headers and openings. Every new window and door in an existing wall means cutting, headers, and patching. Conversions wanting lots of light pay for each opening in a way new construction doesn't.

The takeaway: get eyes on these six items before you budget — a pre-design assessment costs a few hundred dollars and prevents $50K surprises. A conversion quote that never mentions your foundation isn't a quote; it's a wish.