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Module 12 · Lesson 1

ADU Construction From Start to Finish

2 min readWritten lesson

Site prep to certificate of occupancy — every construction stage, how long each takes, and where the inspections land. The homeowner's map to the build.

Permit in hand (Module 10), team hired (Module 11) — now the part you've been picturing since lesson 1.1. Construction follows a sequence as fixed as a recipe, because each stage physically depends on the last. Here's the whole arc; the rest of the module zooms into each stage.

The sequence, with typical detached-ADU durations:

  1. Site preparation (1–2 weeks) — demolition, clearing, grading, utility trenching begins (lesson 12.2)
  2. Foundation (2–4 weeks including inspection and cure) — forms, under-slab plumbing, steel, pour (12.3)
  3. Framing (3–5 weeks) — floors, walls, roof; the building appears (12.4)
  4. Roofing, windows, doors (1–2 weeks) — the shell closes; "dried in"
  5. Rough systems (3–4 weeks) — plumbing, electrical, HVAC threaded through the frame (12.8)
  6. Insulation (a few days, after rough inspections pass) (12.9)
  7. Drywall (1–2 weeks) — the inside becomes rooms (12.9)
  8. Finishes (4–8 weeks) — cabinets, tile, flooring, paint, fixtures, appliances (12.10)
  9. Exterior and site completion (overlaps) — stucco/siding, final grading, that landscape repair from Module 6.8
  10. Final inspections and certificate of occupancy (12.12) — then punch list (12.13)

Total: roughly 5–9 months for detached new construction; garage conversions often run 3–5 months (no foundation-from-scratch, no shell). Add weather, inspection scheduling, and material lead times for reality.

The rhythm to expect. Construction is not linear progress — it's bursts and pauses. Foundation week feels dramatic; the two weeks waiting for concrete cure and the framing crew's availability feel like abandonment. Mid-project, rough systems produce weeks of "nothing changed" (everything changed — inside the walls). Then drywall lands and suddenly it's a house. Knowing the rhythm keeps you from panicking at pause #3.

Your job during construction (assuming a GC — Module 11's path): stay reachable for the decisions that are genuinely yours (finish confirmations, discovered-condition change orders), pay milestones per lesson 11.10, resist the urge to redirect trades directly (everything routes through the GC — one conductor per orchestra), and walk the site with the GC on a regular cadence, not daily on your own. Trust the sequence; verify at milestones.

Key takeaways

  • Construction is a fixed sequence: dirt → foundation → frame → shell → systems → insulation → drywall → finishes → final.
  • Detached ADUs run ~5–9 months of construction; conversions ~3–5.
  • Progress comes in bursts and pauses — the quiet weeks are usually systems work, not abandonment.
  • Your role: decide fast when asked, pay at verified milestones, and route everything through the GC.