What's the recommended order for installing underlayment, flooring, door jambs, and baseboards?

Short answer

Install in this order: door jambs (set to finished floor height) → underlayment → flooring → baseboards (then optional shoe/quarter-round).

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Why this order works

• Door jambs first lets you set the door correctly relative to the finished floor so the door isn’t too low (dragging) or too high (big gap). You’ll undercut the jambs so the flooring slides underneath for a clean look.
• Underlayment before flooring is straightforward: it’s the cushion, moisture/vapor layer, or sound barrier that supports the flooring.
• Baseboards last so they cover the flooring expansion gap and any minor edge irregularities. Add shoe molding/quarter-round after if needed, especially with floating floors.

This sequence avoids trapping a floating floor, prevents door clearance issues, and gives the cleanest trim lines.

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Step-by-step guidance

1. Plan the finished floor height

   • Confirm floor type and thickness (e.g., laminate/engineered 3/8–1/2", LVP 4–8 mm, solid hardwood 3/4"). Don’t forget underlayment thickness.
   • Use a scrap of your flooring plus a piece of underlayment as a spacer during door installation.

2. Install door jambs (prehung doors)

   • Shim and plumb the jambs, setting the bottom to allow for the finished floor thickness. Undercut the jamb legs so flooring can slide beneath.
   • If doors are already installed, undercut jambs now.

3. Prep subfloor

   • Ensure it’s clean, dry, and flat. Patch high/low spots per manufacturer specs.
   • Address squeaks by re-screwing subfloor to joists.

4. Lay underlayment

   • Roll out and tape seams per manufacturer instructions. Keep it wrinkle-free.
   • For nail-down hardwood, use 15 lb felt or rosin paper, lapped 2–4".

5. Install flooring

   • Maintain expansion gaps at walls and fixed objects. Use spacers.
   • Work from the longest, straightest wall.
   • Slide boards under the undercut jambs for a seamless threshold.

6. Install baseboards (and shoe molding if used)

   • Baseboards cover the gap; nail to the wall studs, not through a floating floor.
   • Add shoe molding/quarter-round to bridge baseboard to floor without pinning the floor.

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Tools and materials

• Measuring tape, straightedge, chalk line
• Level, framing square
• Shims, spacers
• Oscillating multi-tool or jamb saw (for undercuts)
• Miter saw (trim), coping saw (inside corners)
• Finish nailer (15–16 ga) for baseboards; brad nailer (18 ga) for shoe
• Flooring tools: tapping block, pull bar, rubber mallet
• Underlayment (foam, cork, felt/rosin paper as specified)
• Construction adhesive (optional for baseboard back-beads), caulk, wood filler
• PPE: safety glasses, hearing protection, dust mask/respirator, knee pads

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Key specs to remember

Typical expansion gaps: 1/4" (6 mm) for laminate/LVP; follow brand specs
Door jamb clearance above subfloor: finished floor thickness + 1/16–1/8"
Baseboard height: 3–5" common; nail into studs or bottom plate (not the floor)
Undercut depth: enough for flooring + underlayment to slide freely

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Tips for best results

• Acclimate flooring per manufacturer (often 48–72 hours) and check moisture.
• Undercut before flooring: It’s cleaner and avoids scratching new floors.
• Pre-paint or prime baseboards before installation; touch up nails and caulk after.
• Scribe baseboards to wavy walls; cope inside corners for tighter joints.
• Use a dedicated jamb saw for consistent undercuts; a multi-tool works well for small areas.
• For floating floors, keep trim nails out of the floor—nail into the wall only.

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Common mistakes to avoid

• Installing baseboards before flooring: you’ll expose gaps or overuse quarter-round.
• Not undercutting jambs: leads to awkward L-cuts and visible gaps.
• Pinning a floating floor with nails or adhesive: can cause buckling and noise.
• Forgetting door clearance: doors rub after flooring goes in.
• Skipping subfloor prep: unevenness telegraphs through, causing clicks and movement.

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Flooring-type variations

• Laminate/Engineered floating: Underlayment pad is required unless attached. Strict expansion gap rules.
• Glue-down engineered/LVP: Use manufacturer’s approved adhesive; some skip foam underlayment and use sound/vapor underlayment membranes.
• Nail-down hardwood: Use 15 lb felt/rosin paper; install doors/jambs first, then floor, then baseboards. No shoe is required if your cuts are tight, but many installers still use it.

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Cost and time

• Underlayment: $0.10–$0.75/sq ft (foam/cork); felt/rosin $0.15–$0.30/sq ft.
• Tool rental: jamb saw $30–$50/day; finish nailer kit $30–$40/day.
• Time (typical 200 sq ft room): underlayment 1–2 hrs, flooring 1 day, baseboards 3–5 hrs. Doors: 1–2 hrs per prehung door.

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When to call a pro

• Significant subfloor leveling, moisture issues, or structural door framing needs.
• Complicated transitions, stair nosings, or high-end hardwood where precision is critical.
• Historical trim replication or specialty finishes.

Follow the sequence—jambs set to finished floor height, underlayment, flooring, then baseboards—and you’ll get tighter trim lines, better door function, and a professional finish.