From Skeleton to Skin: Insulation & Drywall
This is the phase where your ADU transforms from an industrial-looking frame into something that actually looks like a home. Insulation goes in to make it comfortable, and drywall covers everything up to create smooth, paintable walls.
Insulation: Your Comfort Layer
Why It Matters
Insulation is the barrier between you and the outside world. Good insulation means:
- Comfortable temperatures year-round
- Lower energy bills (satisfying Title 24)
- Sound dampening between rooms and from outside
- Moisture control
Common ADU Insulation Types
Fiberglass Batts (Most Common)
- Pink or yellow blankets that fit between studs
- R-13 for 2x4 walls, R-21 for 2x6 walls
- Affordable and effective
- Must be installed carefully — gaps reduce performance
Spray Foam
- Applied as a liquid that expands to fill cavities
- Superior air sealing and moisture resistance
- Higher R-value per inch (R-6 for closed-cell)
- More expensive but worth it in specific applications
Blown-In (Cellulose or Fiberglass)
- Great for ceiling/attic insulation
- Fills irregular spaces completely
- R-30 to R-38 in ceilings (Title 24 requirement)
Insulation Inspection
After insulation is installed, the city inspector and a HERS (Home Energy Rating System) rater verify:
- Correct R-values in all assemblies
- No gaps, voids, or compression
- Proper vapor barrier installation
- Air sealing at penetrations (pipes, wires, ducts)
Drywall: Creating Your Walls
The Process
Hanging (1-2 days)
- 4x8 or 4x12 sheets of gypsum board are screwed to studs
- Sheets are staggered at joints for strength
- Special moisture-resistant "green board" is used in bathrooms
- Fire-rated drywall (Type X) is used where required
Taping (1 day)
- Paper or fiberglass tape is applied over all joints
- Joint compound (mud) covers the tape and screw heads
Mudding (2-3 days, multiple coats)
- Two to three coats of joint compound are applied
- Each coat is wider than the last, feathering the edges
- Drying time between coats: 24 hours
Sanding (1 day)
- All joints and patches are sanded smooth
- The goal: invisible seams that disappear under paint
Texture (if desired)
- Smooth finish is most popular for modern ADUs
- Orange peel or knockdown textures are also options
Timeline & Cost
- Insulation: 1-2 days installation, a property-specific written estimate per project
- Drywall: 5-8 days total (with drying time), a property-specific written estimate per project
- Combined, this phase takes about 2 weeks
Coming Up Next
The series continues with finishing trades — paint, flooring, cabinets, fixtures, and all the details that make your ADU beautiful and functional.
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Vision ADU delivers smooth, flawless interiors on every project. Get your free estimate today.
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- How to Build an ADU, Day 13: Bathroom Tile & Shower
- How to Build an ADU, Day 14: Flooring
- How to Build an ADU, Day 15: Cabinets & Countertops
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