Insulation, drywall, finishes

The sequence

1. Insulation — wall, ceiling, floor, per energy code on the new portion. Inspected before drywall.
2. Drywall — hung, taped, mudded, sanded, primed.
3. Trim and millwork — door and window casings, baseboards, built-ins. On an addition, this is where matching the existing house's casing profile actually matters.
4. Cabinets — uppers, lowers, vanities, shelving.
5. Counters — measured after cabinets are in, fabricated and installed.
6. Flooring — sheet, plank, or tile per room. Matching the existing floor stain at the addition tie-in is the trickiest part.
7. Paint — walls and trim.
8. Fixtures and trim-out — light fixtures, plumbing trim, HVAC registers, electrical devices.
9. Appliances.

This is the longest phase by hands-on time, typically 2 to 4 months on an addition (longer than DADU because of the matching-to-existing work).

Where the budget gets eaten

Finishes are roughly 20–30% of total project cost on an addition, and the line where late "we'll just upgrade" decisions eat the contingency. The familiar pattern:

• "We'll just refinish the existing floors too." +$8,000.
• "We'll just do quartz instead of laminate." +$3,000.
• "We'll just go with the better windows." +$5,000.
• "We'll just upgrade the cabinets." +$8,000.

By the end of finishes, $25K–$50K of "we'll just" decisions sit on the change-order ledger. Set the finish budget at design time and treat upgrades as deliberate trades, not impulses.

The matching-to-existing problem

Additions live or die by whether the new work blends with the old. Three matching decisions to make explicitly:

• Trim and casing profiles. Match the existing exactly, or use a deliberate transition detail.
• Floor stain and species. Refinish the whole house? Or accept a visible seam at the transition?
• Exterior siding. Match the existing siding (often impossible if it's discontinued) or wrap the whole house? Wrapping doubles exterior cost but is sometimes the only way to a clean look.