Module 12 · Lesson 9
Insulation and Drywall: The Inside Becomes Rooms
Insulation delivers your Title 24 promises; drywall turns a skeleton into rooms in a week. What happens, what's inspected, and what to check first.
Two stages, one lesson, because together they perform the build's greatest magic trick: skeleton one week, rooms the next.
Insulation (a few days). The Title 24 report (lesson 9.4) made promises — specific R-values in walls, ceiling, and (often) floor; this is where they're kept. Batts, blown, or spray foam fill every cavity, plus the details that separate good jobs from checked boxes: sealed penetrations, insulation behind pipes (pipes on the warm side stay happy), and — if your design used it — the sound insulation in interior walls around bedrooms and baths, and in any wall shared with the main house (lesson 8.5's attached-unit spec, installed now or never). An insulation inspection verifies values and coverage before anything gets covered. One homeowner move worth making: this is the final moment to photograph your walls open. Twenty minutes of phone photos of every wall = a permanent map of every pipe and wire you'll ever want to find. Future-you, hanging a TV, says thanks.
Drywall (1–2 weeks). Hanging goes fast — sheets on every wall and ceiling in a day or two, and suddenly the ADU has rooms, real acoustics, and a size (smaller than the frame suggested, then bigger again once painted — every project, every time). Then the slower craft: taping, mudding in coats, sanding — the finish quality of every wall you'll ever look at is set right here, in the patience of the mud work. Texture (or smooth finish, the premium look) wraps it.
What to check on your walk-through: raking light across walls reveals mud quality (good crews invite this test); confirm the access panels where code requires them; and notice the quiet — a drywalled ADU with insulated walls sounds like a home for the first time. That sound is lesson 8.5's privacy engineering, audible.
Why this stage lifts morale: it's the visible one-way door. Before drywall, the project reads as construction; after, it reads as almost home — and the finish stage (12.10) inherits all that momentum. Enjoy it. You've earned a good week.
Key takeaways
- Insulation is Title 24's promises kept — inspected before covering, including any sound-wall specs.
- Photograph every open wall before drywall: a permanent map of pipes and wires, free.
- Drywall's speed is in the hanging; its quality is in the mud — check walls with raking light.
- This is the build's morale turn: from "construction site" to "almost home" in two weeks.