Interior Trim: Complete Guide

Overview

• Typical Duration: 2-3 weeks
• DIY Difficulty: ⭐⭐⭐☆☆ (3/5)
• Typical Cost: $6,000-$20,000 (2,000 sq ft house, varies greatly by trim level)
• When to Hire: Very DIY-able with patience
• Required Inspection: No

Interior trim transforms painted drywall into finished rooms. This is detail work that requires patience and precision, but it's very DIY-able and saves significant money. Quality trim installation elevates the entire home's appearance.

I've seen owner-builders with no carpentry experience successfully trim their homes, saving $4,000-$8,000 in labor. The key is working slowly, measuring carefully, and not being afraid to recut pieces.

When This Phase Happens

Trim installs after drywall is complete and painted (or primed minimum).

Must be complete first:

• Drywall installed and finished
• Walls primed (painting first coat is better)
• Flooring installed OR accounted for in measurements

Can happen in parallel:

• Final painting (trim walls first, install trim, paint trim)
• Flooring (if doing trim-first method)

What comes after:

• Final painting
• Flooring (if using trim-last method)
• Final fixtures and hardware

Should You DIY This Phase?

DIY If:

• Can measure carefully and cut accurately
• Have basic carpentry skills
• Have patience for detail work
• Can handle a miter saw safely
• Have time (trim takes longer than you think)
• Want to save $4,000-$8,000 in labor

Hire Out If:

• Complex crown molding (professionals make it look easy - it's not)
• Intricate details or curved work
• Don't own or can't rent proper tools
• Limited time
• Want perfect miters without practice

My recommendation: DIY baseboard and door trim (straightforward), consider hiring for complex crown molding. Baseboard is the most forgiving place to learn - it's close to the floor where small gaps are less visible.

Start with closets and utility rooms to practice. By the time you reach main living areas, you'll have developed the skills.

Materials Needed

Trim Materials (2,000 sq ft house - costs vary enormously by style)

Budget trim package ($2,000-$4,000 materials):

• Pine or MDF baseboard (3-1/4" colonial style)
• Pine door and window casing (2-1/4" colonial style)
• Hollow core pre-hung interior doors

Mid-grade trim package ($4,000-$8,000 materials):

• Poplar or primed MDF baseboard (5-1/4" profile)
• Poplar casing (3-1/2" craftsman style)
• Solid core pre-hung doors
• Simple crown molding

High-end trim package ($8,000-$15,000+ materials):

• Hardwood baseboard (oak, maple) with cap molding
• Hardwood casing with rosette blocks
• Custom solid wood doors
• Multi-piece crown molding
• Wainscoting, chair rail, picture rail

Typical mid-grade materials:

Fasteners and Materials

Tools Required

Essential:

• 10" or 12" compound miter saw (rent $40-$60/day or buy $200-$500)
• 15 or 16 gauge finish nailer (rent $25-$40/day or buy $150-$350)
• Air compressor (rent $40-$60/day)
• Tape measure (25 ft)
• Speed square and combination square
• Level (4-foot and torpedo)
• Coping saw (for inside corners)
• Nail set (for hand-nailing)
• Hammer
• Utility knife
• Pencil

Nice to have:

• Pneumatic brad nailer (18 gauge for small pieces)
• Cordless finish nailer (no compressor needed)
• Compound miter saw with laser guide
• Crown molding jig
• Block plane
• Caulk gun with quality tips

Step-by-Step Process

Days 1-3: Interior Door Installation

Pre-hung door installation (much easier than slab doors):

1. Verify rough opening: Should be 2" wider and taller than door frame
2. Test fit: Set door unit in opening
3. Shim hinge side:
   • Place shims at each hinge location
   • Make hinge jamb perfectly plumb
   • Nail through jamb and shims into framing
4. Shim strike side:
   • Adjust to maintain even gap (1/8" around door)
   • Check door operation (should swing freely)
5. Shim head:
   • Level across top
   • Maintain even reveal
6. Secure jamb: Finish nail through shims into framing (every 12")
7. Test operation: Door should swing freely, latch properly
8. Cut shims flush: Score with knife, snap off
9. Install casing later (after all doors are hung)

Days 4-8: Baseboard Installation

Baseboard is the best place to start - low to floor, gaps less visible, builds confidence.

Inside corners (use coped joints - superior to miters):

1. First piece: cut square, install into corner
2. Second piece:
   • Miter at 45° (like inside miter)
   • Use coping saw to cut along profile line revealed by miter
   • Coped profile fits over first piece perfectly
   • Test fit, sand or trim as needed for perfect fit

Outside corners (45° miters):

1. Cut both pieces at 45°
2. Apply wood glue to miter joint
3. Nail pieces to wall
4. If gap at corner, apply wood filler and sand smooth

Straight runs:

1. Measure and cut to length
2. Locate studs (nail into studs, not just drywall)
3. Apply small amount of construction adhesive to back
4. Nail at bottom (through baseboard into sole plate)
5. Nail at top (into studs)
6. Fill nail holes with wood filler

Dealing with out-of-level floors:

1. Scribe baseboard to follow floor contour
2. Use compass or scrap wood to mark
3. Cut along scribe line
4. Base shoe molding covers remaining gap

Days 9-13: Door and Window Casing

Door casing (picture frame style - most common):

1. Install side casing first:
   • Reveal jamb edge by 1/8" to 1/4" (consistent reveal is critical)
   • Cut to length, miter top at 45°
   • Nail to jamb and framing
2. Install head casing:
   • Miter both ends at 45°
   • Test fit before nailing
   • Adjust length if miters don't close perfectly
   • Nail to jamb and framing

Window casing (stool and apron style):

1. Install window stool (sill) first:
   • Extend past casing by 1/2" to 3/4" each side
   • Notch to fit against window jamb
   • Level and nail to framing
2. Install side and head casing:
   • Same as door casing
   • Sits on stool at bottom
3. Install apron under stool:
   • Cut to match outer edge of casing
   • Return ends or cut square

Tips for perfect miters:

• Use sharp saw blade (dull blades tear wood)
• Support long pieces properly
• Make test cuts on scrap before cutting good pieces
• Undercut slightly rather than overcut (1/8° makes big difference)
• Use glue on all miter joints
• For gaps: use wood filler on paint grade, recut on stain grade

Days 14-16: Crown Molding (Optional)

Crown molding is the hardest trim work. Consider hiring if you want extensive crown.

Understanding crown angles:

• Crown molding installs at an angle (typically 38° or 45° spring angle)
• Miter saw settings must account for this angle
• Use crown molding jig or lay molding upside down against fence

Basic crown installation:

1. Start at longest wall without openings (practice wall)
2. Cut square on one end, install in corner
3. Cut cope joint for adjoining piece (like baseboard)
4. Work around room, coping all inside corners
5. Miter all outside corners
6. Nail to ceiling joists and wall studs (blocking may be needed)

Days 17-20: Finishing Work

Closet shelving:

• Install shelf standards or wood cleats
• Cut wire shelving or wood shelving to fit
• Install closet rod at proper height (66-68")

Handrails:

• Install brackets per code (36" height typical)
• Continuous handrail on stairs
• Returns to wall at top and bottom

Final details:

• Window stools and stops
• Specialty moldings (chair rail, picture rail if specified)
• Built-in details (bookcase trim, fireplace mantel)

Caulking:

• Caulk all joints between trim and walls/ceiling
• Use paintable acrylic latex caulk
• Tool smooth with wet finger
• Don't caulk trim joints (wood moves, caulk cracks)

Fill nail holes:

• Use appropriate filler (stain-grade vs paint-grade)
• Overfill slightly
• Sand flush after drying

Trim Styles

Colonial/Traditional:

• Simple profiles with curves
• 3-4" baseboard, 2-3" casing
• Modest crown molding
• Most common and forgiving for DIY

Craftsman:

• Flat, wide profiles
• 5-7" baseboard, 3-4" casing
• Often with back-band or cap moldings
• Clean lines, easier miters

Modern/Contemporary:

• Minimal or no trim
• Flat stock or reveal details
• Very simple profiles
• Requires perfect drywall finishing

Victorian/Ornate:

• Complex multi-piece profiles
• Large baseboards (8"+)
• Elaborate crown molding
• Rosette blocks, plinth blocks
• Hire professionals for this style

Code Requirements

Limited code requirements for trim:

• IRC R311.7.8 - Stair handrails: Required for 4+ risers, 34-38" height, returns to wall

• IRC R315 - Handrail graspability: 1-1/4" to 2" diameter, 1-1/2" clearance to wall

Most trim work has no code requirements - it's aesthetic choice.

Subcontractor Considerations

Typical pricing:

• Baseboard installation: $2.00-$4.00 per LF installed
• Door casing: $50-$100 per opening installed
• Window casing: $75-$150 per window installed
• Crown molding: $4.00-$8.00 per LF installed
• Door hanging: $75-$150 per door

Example costs (2,000 sq ft house, mid-grade trim):

• Materials: $4,000-$8,000
• Labor: $4,000-$8,000
• Total: $8,000-$16,000

Timeline: 7-14 days for typical house

What to look for:

• Experience with residential trim
• Portfolio of previous work
• Attention to detail
• Clean, tight miters
• References from similar projects

Common Mistakes

1. Not Accounting for Flooring

Why it's a problem: Baseboard too low (gap at floor) or too high (doesn't reach floor after flooring installed). How to avoid: Know final floor height. Install flooring first OR account for flooring thickness in baseboard height. Cost if you don't: $500-$2,000 to remove and reinstall baseboard.

2. Inconsistent Reveals

Why it's a problem: Looks unprofessional, draws eye to imperfections. How to avoid: Use consistent reveal (1/8" to 3/16") everywhere. Mark reveal on jambs before installing casing. Cost if you don't: Poor appearance, may need to remove and reinstall.

3. Dull Saw Blade

Why it's a problem: Rough cuts, torn wood grain, fuzzy miters that don't close. How to avoid: Use sharp, fine-tooth blade (60-80 teeth for finish work). Replace or sharpen regularly. Cost if you don't: Wasted material, poor-looking joints.

4. Not Using Glue on Miters

Why it's a problem: Miters open up over time as wood shrinks. How to avoid: Always apply wood glue to miter joints before nailing. Wipe excess immediately. Cost if you don't: Gaps at miters, poor appearance.

5. Wrong Nail Placement

Why it's a problem: Splits wood, doesn't hit framing, nails show. How to avoid: Nail into studs/framing, not just drywall. Keep nails back from ends (1-1/2" minimum). Pre-drill hardwoods. Cost if you don't: Split trim, loose trim, visible nails.

6. Not Coping Inside Corners

Why it's a problem: Mitered inside corners open up as wood shrinks, look terrible. How to avoid: Learn to cope baseboard and crown inside corners. It's worth the effort. Cost if you don't: Gaps at corners, unprofessional appearance.

7. Over-Caulking

Why it's a problem: Looks messy, cracks as wood moves, hard to paint. How to avoid: Small bead only. Tool smooth immediately. Only caulk trim-to-wall, not trim-to-trim joints. Cost if you don't: Poor appearance, cracking caulk.

8. Not Pre-Finishing

Why it's a problem: Harder to paint after installation, paint gets on walls. How to avoid: Prime and first coat trim before installation. Touch up after install. Final coat after install if careful. Cost if you don't: Difficult painting, paint on walls, more time.

9. Forcing Doors

Why it's a problem: Bowed jambs, doors that don't close properly, broken hinges. How to avoid: Shim carefully. Doors should close with minimal effort. Check operation before final nailing. Cost if you don't: $200-$500 per door to remove and reinstall properly.

10. Not Allowing for Wood Movement

Why it's a problem: Trim buckling, gaps opening, cracks. How to avoid: Don't force pieces to fit perfectly. Leave small gaps (filled with caulk). Use finish nails (allow some movement). Cost if you don't: Buckled trim, visible gaps, cracking.

Quality Checkpoints

Before considering trim complete:

• [ ] All doors hung and operating smoothly
• [ ] All door casings installed with consistent reveals
• [ ] All window casings installed
• [ ] All baseboard installed with tight corners
• [ ] All outside corners mitered tight
• [ ] All inside corners coped properly
• [ ] Crown molding installed (if specified)
• [ ] All nail holes filled and sanded
• [ ] All trim caulked to walls/ceiling
• [ ] No split or damaged pieces
• [ ] All closet shelving installed
• [ ] Handrails installed per code (stairs)
• [ ] All trim primed/painted or stained
• [ ] No visible gaps larger than 1/8"
• [ ] Clean, professional appearance

Budget Breakdown

Example for 2,000 sq ft house, mid-grade trim:

Timeline Tips

Scheduling:

• Install after drywall painting (at least primer coat)
• Before or after flooring (depends on method chosen)
• Allow time for caulking and fill to dry before final painting
• Work room by room for satisfaction and organization

What Comes Next

After interior trim complete:

1. Final painting (walls and trim)
2. Flooring installation (if trim-first method)
3. Final fixtures (lights, hardware, plumbing fixtures)

Link to: Flooring Phase

Related Resources

• Trim Styles Guide
• Coping Joints Tutorial
• Door Installation Guide

Need Trim Help?

Interior trim requires patience and precision but is very DIY-able. If you're unsure about coping joints or complex crown molding, a consultation can help you master these skills.