Short answer
Colonial casing has a stepped cove-and-bead profile and reads as traditional. Ranch casing, also called clamshell, is a simple taper with a rounded outer edge and reads as plain and mid-century. Both are typically 5/8 to 11/16 in thick and 2-1/4 in wide, sold primed or in wood, and mitered at the head. Pick colonial for traditional rooms; pick ranch for ranch houses, rentals and quick matches.
The profiles side by side
| Colonial | Ranch | |
|---|---|---|
| Shape | Bead at the jamb edge, flat, then cove and bead (ogee) at the outside | Smooth taper, rounded outer edge |
| Typical size | 11/16 x 2-1/4 in; wider versions around 3-1/4 in | 5/8 x 2-1/4 in |
| Reads as | Traditional, detailed | Plain, mid-century, utilitarian |
| Head joint | Mitered | Mitered |
| Forgiveness | Detail helps disguise small gaps | Plain face shows every gap at the miter |
This Old House describes colonial casing as traditional and versatile, typically with a cove-and-bead profile (This Old House). Both profiles are thickest at the outer edge, so the baseboard can butt into the casing without standing proud of it.
-
01Traditional
Colonial casing, 2-1/4 in
Best for: traditional rooms with 8 ft ceilings
- Size
- 11/16 x 2-1/4 in
- Lengths
- 7 ft and longer
- Material
- MDF, pine, hardwood
- The stock colonial size at most home centers
- Primed MDF is the low-cost paint-grade choice in dry rooms
- Check the length: 7 ft pieces fit one leg of an 80 in door
-
02Plain
Ranch casing, 2-1/4 in
Best for: ranch houses, rentals, closets and utility rooms
- Size
- 5/8 x 2-1/4 in
- Lengths
- 7 ft and longer
- Material
- MDF, pine, oak
- Simple shape that suits plain doors
- Some sold prefinished in polystyrene for damp rooms (maker claim)
- Plain face means miters must close tight
Which one should you buy?
- Traditional, colonial or transitional house: colonial. Go to about 3-1/4 in on taller ceilings.
- Ranch or mid-century house: ranch, or a slim modern flat casing.
- Matching existing trim: take an offcut. Catalog numbers such as 356 mean different profiles at different makers.
- Want more presence? Add a backband around the outside edge of colonial casing to make it look wider and heavier.
Ready to buy? Work out the lengths with the casing calculator, then read how to install door casing.
Questions people ask
What does 356 casing mean?
It is a catalog number, not a style. Different makers use 356 for different profiles: one listing calls a 356 casing ranch, another sells a WM356 colonial casing at 11/16 by 2-1/4 inches. Always check the profile drawing and the stated size, not just the number.
Is ranch casing cheaper than colonial?
Often slightly, because the profile is simpler, but material matters more than shape. Fixr lists basic colonial casing at about $1 to $5 per linear foot and ranch at about $2 to $6 for interior trim, so the ranges overlap.
Can I mix colonial and ranch in one house?
You can, but designers generally suggest one profile through a floor. If you are replacing damaged trim, match what is there by taking an offcut to the store.
Sources
Last reviewed October 12, 2026. Profiles, sizes and listings change; check the product details before you buy, and follow the maker’s instructions.