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The door trim guide

Door molding, drawn to the detail

Door molding, or casing, frames a door opening and hides the gap between the jamb and the wall. Three choices decide how it looks and how hard it is to fit: the profile, the width and joint at the head, and the material. Most interior casing is 2-1/4 to 3-1/2 inches wide, and one side of a standard door takes about 17 linear feet.

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FIVE CASING PROFILESDrawn to the same scaleCOLONIAL11/16 x 2-1/4 inRANCH5/8 x 2-1/4 inCRAFTSMAN FLAT3/4 x 3-1/2 inFARMHOUSE FLAT3/4 x 3-1/2 inMODERN SQUARE1/2 x 2-1/2 in
Plate 1 Five common casing profiles, drawn to the same scale. Sizes are typical stock sizes; makers vary.
01

Five casing styles

The profile is the shape you see in section. It sets the character of the whole room, so start here. The casing styles guide compares them side by side.

11/16 x 2-1/4 inColonialCove-and-bead profile. The default in traditional homes.5/8 x 2-1/4 inRanchA plain tapered profile with a rounded edge. Easy to live with.3/4 x 3-1/2 inCraftsman flatWide flat legs and a built-up head with a cap.3/4 x 3-1/2 inFarmhouse flatFlat boards, butted joints, often on plinth blocks.1/2 x 2-1/2 inModern squareSlim, square and quiet, or no visible casing at all.
02

Three decisions, in order

Get these three right and the rest is carpentry.

  1. Profile

    Match the house. Colonial for traditional rooms, flat stock for craftsman and farmhouse, slim square casing for modern. Keep one profile through a floor so rooms read as one house (This Old House).

  2. Width and joint

    Taller ceilings carry wider casing. Mitered heads suit lower ceilings; butted heads allow a thicker, wider head and are easier to cut (This Old House). Rosettes remove the miters entirely.

  3. Material

    Primed MDF for painted trim in dry rooms, finger-joint pine or PVC where it gets damp, solid wood if you want to stain. MDF vs pine vs PVC.

03

Pick a trim style

Five taps: house style, ceilings, finish, rooms and how you feel about miters. You get a profile, a width, a joint, a material and two searches for it.

1 What style is the house?
2 How tall are the ceilings?
3 Painted or stained trim?
4 Which rooms?
5 How do you feel about miter cuts?

Your trim

04

The parts of door trim

Casing gets the attention, but a finished doorway has a few more pieces. Typical stock sizes below; makers vary, so check the listing.

Door trim parts at a glance

PartTypical sizeWhat it does
Casing5/8 to 3/4 x 2-1/4 to 3-1/2 inFrames the opening and covers the joint between jamb and wall.
Stop molding7/16 x 1-3/8 inNailed to the jamb face. The door closes against it.
Brick mold1-1/4 x 2 inThe heavy exterior casing around entry doors.
Header or crownbuilt upA frieze board, cap or crown over the head casing.
Rosettecasing width plusA square block at the top corners in place of a miter.
Plinth blocktaller than baseA block at the foot of each leg where baseboard meets casing.
PLAN / DOOR, STOP AND CASINGDOOR, CLOSEDSTOPJAMBCASINGDRYWALLSTUDSHIM GAP
Fig. 2 Plan section through a jamb: the door closes against the stop, and casing covers the jamb edge on both faces.
05

Measure, fit and finish

Step-by-step guides for the jobs people actually do, plus what it costs to buy or hire out.

OPENING3/16 IN REVEALPENCIL MARKS ON JAMB EDGE45 DEG MITERDETAIL / THE REVEALCasing set back from the jamb edgeInstall and costHow to install door casing DETAIL / HEAD CASINGWhere to measure a mitered headLONG POINT TO LONG POINTSHORT POINT TO SHORT POINT45SHORT = OPENING + 2 REVEALSLONG = SHORT + 2 CASING WIDTHSInstall and costHow to measure for door trim PAINTER TAPE ON WALLWET EDGEPRIMEDInstall and costHow to paint door trim Install and costDoor trim cost KIT / ONE SIDE OF ONE DOORTwo legs, one head, factory miteredCUT TO LENGTH HERELEG, LEFTLEG, RIGHTHEADParts and materialsDoor trim kits Casing stylesRosettes and plinth blocks Casing stylesDoor header and crown trim Casing stylesDoor molding ideas
06

Shop by part

Straight to current listings. Read the matching guide first if you are not sure which profile or size you need.

07

Questions people ask

Is door molding the same as door casing?

In everyday use, yes. Casing is the molding that frames a door opening and covers the gap between the door jamb and the wall. Door trim is the wider term: it also takes in the stop molding on the jamb, the header or crown over the door, plinth blocks, rosettes and, outside, brick mold.

What size door casing is most common?

This Old House puts typical door trim at 2-1/4 to 3-1/2 inches wide, with craftsman trim often 4 inches or wider. Stock colonial and ranch casing is commonly 2-1/4 inches wide and around 5/8 to 11/16 inch thick.

How much casing do I need for one door?

For a 32 by 80 inch door with 2-1/4 inch mitered casing, one side takes about 17 linear feet: two legs of about 82-1/2 inches and a head of about 37 inches. Fixr also suggests planning on at least 17 linear feet per door. Double it to trim both sides, and use the casing calculator for your sizes.

Should I buy MDF or wood door casing?

For painted trim in dry rooms, primed MDF is the low-cost, smooth choice. For bathrooms, laundry rooms and basements, primed finger-joint pine or PVC handles moisture better. For stained trim you need solid wood, because MDF cannot take stain.

How much does it cost to trim a door?

Fixr puts professional door trim installation at $150 to $250 per door, with a national average of $175, and casing materials from under $1 to several dollars per linear foot depending on material and profile.

Sources: This Old House, Fixr, Intrim, Fine Homebuilding. We have not tested these products; see how we choose.