Baseboard & Casing Installation Guide

Complete guide to baseboard and casing installation covering baseboard coping techniques, door casing reveals, window stool and apron installation, nail patterns, returns vs plinth blocks, and finishing with caulk and putty.

Baseboard Installation Techniques

Critical Baseboard Corner Techniques

Like crown molding, baseboard inside corners should be coped, not mitered. Coped joints remain tight as the wood moves with seasonal changes. Outside corners are always mitered at 45 degrees.

Best Practice: Cope inside corners, miter outside corners, scarf joints at studs

Baseboard Corner Techniques

Corner Type	Technique	Process
Inside corner	Cope the joint	Cut 45° miter, then cope profile with coping saw
Outside corner	Miter at 45 degrees	Both pieces cut at 45°, glue and nail together
Scarf joint (long runs)	45° beveled scarf	Join over stud, upper piece overlaps lower

Coping Baseboard Inside Corners

1.First piece: Install with square cut butting into corner
2.Cut miter: Cut 45° inside miter on second piece to expose profile
3.Mark profile: Darken profile line with pencil for visibility
4.Cope with saw: Cut along profile with coping saw or jigsaw
5.Back-cut: Angle cut back slightly for tight face fit
6.Test and adjust: Fit to first piece, sand high spots

Baseboard Nailing Pattern

Locate studs: Use stud finder, mark with light pencil
Spacing: Nail every 16 inches into studs
Two nails per stud: One high, one low for secure hold
Top nail: Into stud 1" from top edge
Bottom nail: Into bottom plate 1" from bottom edge
Nail size: 2" to 2-1/2" finish nails or 16-gauge brads

Base Shoe Molding

Purpose: Covers gap between baseboard and floor, accounts for uneven floors
Material: Quarter round or base shoe (1/2" × 3/4" typical)
Installation: Nail into floor (not baseboard) to allow wood movement
Inside corners: Cope base shoe like baseboard for tight fit
Outside corners: Miter at 45 degrees like baseboard
Nail spacing: Every 12-16 inches into floor or subfloor
Alternative: Can caulk baseboard-to-floor gap instead if floor is level

Door Casing Installation

Door Casing Reveal

The reveal is the setback of the casing from the jamb edge. A consistent reveal creates a professional appearance and shadow line that defines the door opening.

Standard Reveal: 1/8 inch to 1/4 inch from jamb edge (3/16 inch is most common)

Door Casing Specifications

Component	Measurement	Notes
Reveal from jamb edge	1/8" to 1/4" (3/16" typical)	Consistent on all three sides
Head/side miter joint	45 degrees	Must align perfectly on face
Side casing length	Floor to underside of head casing	Measure after head casing installed
Nailing - reveal edge	2" finish nails into jamb	Every 12-16 inches
Nailing - outside edge	2-1/2" nails or brads into stud	Every 16 inches

Door Casing Installation Steps

1.Mark reveal: Set marking gauge to 3/16", mark jamb perimeter
2.Cut head casing: Square cut to length, add casing width × 2 + jamb width
3.Miter ends: 45° miters on both ends of head casing
4.Install head: Align to reveal marks, nail into head jamb and framing
5.Cut side casings: 45° miter on top, square cut on bottom
6.Fit miters: Adjust length until miter joints close perfectly
7.Install sides: Nail reveal edge into jamb, outside into framing
8.Pin miters: Brad nail through miter joint from side piece into head

Baseboard-to-Door Casing Transitions

Option 1: Returns (Most Common)

• Baseboard dies into side casing at 45° angle
• Create small return piece to finish end
• Return wraps baseboard profile back to wall
• Clean, professional appearance

Option 2: Plinth Blocks

• Decorative block at base of door casing
• Thicker and taller than casing
• Baseboard butts into plinth (square cut)
• Traditional, formal appearance

Window Casing Installation

Window Casing Components

Window casing differs from door casing by including a stool (interior sill) and apron. The stool projects beyond the casing, and side casings sit on top of the stool.

Key: Stool projects 3/4" to 1" past casing, side casings rest on stool surface

Window Trim Components & Measurements

Component	Measurement/Specification	Purpose
Stool (sill)	Projects 3/4" to 1" past casing	Interior sill, decorative shelf
Stool length	Jamb width + 2× casing width + 2× projection	Extends past casings on both sides
Side casing	Rests on stool surface	Vertical trim on sides of window
Head casing	Miters to side casings at 45°	Top horizontal trim
Apron	Under stool, same length as head casing	Supports stool visually, covers gap

Window Stool Installation

1.Measure width: Inside jamb width + reveal on each side
2.Measure length: Width + 2× casing width + 2× projection (3/4-1")
3.Notch corners: Cut notches to fit around side jambs
4.Test fit: Should sit level and tight to bottom jamb
5.Shim if needed: Level stool with shims underneath
6.Nail: Face nail into sill and shims with finish nails
7.Create returns: Miter profile at ends, glue return pieces

Window Casing & Apron

Mark reveal: 3/16" from jamb edge on three sides
Side casings: Bottom rests on stool, top miters to head
Head casing: 45° miters on ends, same length as stool (visible portion)
Install order: Stool first, then sides, then head, finally apron
Apron: Cut to length of head casing, nail to wall under stool
Apron returns: Miter ends and create small return pieces

Stool Profile Options

Flat stool: Simple 1× material (1x4 or 1x6), easiest installation
Beveled stool: Angled front edge, more formal appearance
Bullnose stool: Rounded front edge, classic style
Custom milled: Matching room trim profile, high-end look
Thickness: 3/4" to 1-1/8" typical, thicker = more substantial
Material: Pine, poplar, oak, or pre-primed MDF

Nailing Patterns & Techniques

Door/Window Casing Nailing

Reveal edge: 2" finish nails into jamb every 12-16"
Outside edge: 2-1/2" nails into framing every 16"
Brads on outside: Can use 18-gauge brads for minimal holes
Miter joints: Brad nail through from one piece into other
Pre-drill hardwood: Prevents splitting near ends
Set nails: Use nail set to countersink 1/16" below surface

Baseboard Nailing Pattern

Into studs: Nail every 16" into wall studs
Two nails: One high (into stud), one low (into plate)
Near corners: Nail within 6" of inside and outside corners
Nail size: 2" to 2-1/2" finish nails or 16-gauge
Base shoe: Nail into floor, not baseboard (allows movement)
No studs?: Use construction adhesive plus few nails

Pneumatic Nailer Settings

Finish nailer: 15 or 16-gauge, 1-1/4" to 2-1/2" nails, for baseboard and casing
Brad nailer: 18-gauge, 5/8" to 2" brads, for delicate trim and pinning
Air pressure: 70-120 PSI typical, adjust for wood hardness
Depth adjustment: Set so nail is flush or slightly below surface
Test fire: Always test on scrap piece first to check depth
Safety: Never bypass safety tip, keep away from body parts

Step-by-Step Installation Process

Measure & Plan Room Layout

•Measure all wall lengths, noting door and window locations
•Calculate baseboard material needed: add 10% for waste
•Calculate casing material: each door needs approximately 17 linear feet
•Each window needs approximately 20 linear feet including stool and apron
•Plan installation order: typically baseboard first, then doors, then windows
•Mark stud locations on walls before starting installation

Install Baseboard - Starting Wall

•Choose least visible wall as starting point (often behind door)
•Cut first piece to length with square cuts on both ends
•This piece butts into corners - subsequent pieces cope to it
•Locate studs along wall, mark with light pencil
•Hold baseboard in place, check for gaps at floor
•Nail top edge into studs, bottom edge into bottom plate
•Nail every 16 inches: one nail high, one nail low

Cope Baseboard Inside Corners

•Measure next wall length, add 1/4 inch for coping adjustment
•Cut 45-degree inside miter on end that meets previous piece
•Miter cut exposes baseboard profile - darken with pencil
•Use coping saw or jigsaw to cut along profile line
•Back-cut slightly (5-10 degrees) for tight face fit
•Test fit against installed piece, adjust with rasp or sandpaper
•When fit is perfect, install with same nailing pattern
•Continue around room, coping each inside corner

Miter Baseboard Outside Corners

•Measure to outside corner, cut both pieces slightly long
•Cut 45-degree miters on both pieces (right and left)
•Test fit - adjust length if needed for tight miter joint
•If corner is not exactly 90 degrees, adjust miter angles
•Apply wood glue to miter surfaces before installing
•Nail both pieces, with nails within 6 inches of corner
•Pin miter together by brad nailing through joint from both sides
•Miter should be tight on face with no gaps

Install Base Shoe or Quarter Round

•Install after baseboard is complete and before caulking
•Follows same corner techniques: cope inside, miter outside
•Cut pieces to fit between walls and corners
•IMPORTANT: Nail into floor/subfloor, NOT into baseboard
•This allows baseboard to move with humidity without gaps
•Use 1-1/4 inch finish nails or 18-gauge brad nails
•Nail every 12-16 inches along length
•Set nails below surface, fill holes later

Install Door Casing - Set Reveal

•Set marking gauge or combination square to 3/16 inch
•Mark reveal line on all three sides of door jamb
•Reveal line is where inside edge of casing will align
•Keep reveal consistent on head jamb and both side jambs
•This creates shadow line and professional appearance
•Lightly mark with sharp pencil - will be covered by casing

Cut & Install Door Casing

•Measure and cut head casing: jamb width + 2× casing width
•Cut 45-degree miters on both ends of head casing
•Position head casing on reveal marks, nail into jamb and framing
•Measure side casings: floor to underside of head casing
•Cut 45-degree miter on top, square cut on bottom
•Fine-tune length until miter joints close perfectly
•Install side casings: nail reveal edge into jamb, outside into framing
•Pin miter joints with brads from side casing into head casing

Install Window Stool

•Measure stool length: jamb width + 2× casing width + 2× projection
•Typical projection: 3/4 inch to 1 inch beyond casing face
•Cut notches at corners to fit around side jambs
•Depth of notch: distance from inside edge of jamb to wall surface
•Width of notch: equal to projection plus casing thickness
•Test fit stool - should sit tight to bottom jamb and be level
•Shim if needed to achieve perfect level
•Nail through face into sill and shims with finish nails

Install Window Casings & Apron

•Mark reveal on top and side jambs (3/16 inch typical)
•Cut side casings: bottom edge rests on stool, top miters to head
•Install side casings with same nailing pattern as doors
•Cut head casing to length with 45-degree miters on ends
•Install head casing, check miter joints close tightly
•Cut apron to same length as head casing
•Position apron under stool, centered on window
•Nail apron to wall framing, pulling up tight to underside of stool

Caulk, Fill & Finish

•Fill all nail holes with wood filler or painter's putty
•Use nail set to ensure nails are countersunk before filling
•Let filler dry completely (typically 30 minutes to 2 hours)
•Sand filled nail holes flush with trim using 150-grit sandpaper
•Caulk seam between baseboard and wall with paintable caulk
•Caulk seam between casing and wall on doors and windows
•DO NOT caulk coped joints - properly fit joints need no caulk
•Small gaps in outside miters can be filled with caulk
•Wipe excess caulk with damp finger or rag for smooth finish
•Prime and paint all trim (2 coats for best coverage and durability)

Best Practices & Common Mistakes

DO:

Cope all baseboard inside corners - never miter them
Maintain consistent 3/16 inch reveal on door and window casing
Nail base shoe into floor, not baseboard (allows wood movement)
Pin miter joints together with brad nails for tight fit
Back-cut coped joints 5-10 degrees for tight face fit
Caulk baseboard-to-wall and casing-to-wall seams before painting
Pre-drill hardwood trim near ends to prevent splitting
Use wood glue on all miter joints before nailing

DON'T:

Miter baseboard inside corners (gaps open with wood movement)
Install casing without marking reveal lines first (inconsistent appearance)
Nail base shoe into baseboard (prevents movement, causes gaps)
Forget to back-cut coped joints (won't fit tight to first piece)
Caulk coped joints (properly fit joints don't need caulk)
Use too much caulk (creates messy appearance, hard to paint)
Skip filling nail holes before painting (very visible after paint)
Assume corners are square (measure and adjust miter angles)