Giovanni Valle is a licensed architect and LEED-accredited professional and is certified by the National Council of Architectural Registration Boards (NCARB). He is the author and managing editor of various digital publications, including BuilderSpace, Your Own Architect, and Interiors Place.
Trim is a general term used to describe the material used around openings such as windows and doors, at the corners between walls and ceilings, or at floor intersections. Trim can also be applied in the middle of walls, such as in the case of a chair rail or, by extension, wainscoting.
While molding is a type of trim, it is characterized by its enhanced profile. Typically, molding is more decorative and elaborate in detail. An example is crown molding used at the intersection between walls and the ceiling to add visual interest or soften the transition between wall and ceiling.
Types of Trim Molding
Trim molding falls into four main categories depending on whether it is installed around openings, the ceiling, the floor, or directly on the wall. Casing trim is placed around openings, such as windows and doors.
Baseboards are positioned along the bottom of walls, while crown molding is installed at the top near the ceiling. Finally, all trim placed directly on walls, not at openings or corners, is referred to as wall trim.
Window and Door Casing
Casing is a type of trim that is used around openings. Doors and windows are the most common locations. Casing serves as a frame around openings and helps to cover gaps between the walls and window or door units.
Casing is installed at the top and alternate sides of door openings. At window openings, casing can be installed on all four sides of the window. Typically, however, the bottom portion of the opening has a stool and apron and the casing is installed at the top and sides.
Baseboard trim, also called wall base molding, is installed at the bottom of walls. In addition to providing an accent to the wall, baseboards help hide imperfections in construction between the flooring and the walls of a room.
It is usually mitered at outside corners and coped at inside corners. If the floor is to be carpeted, base molding is usually installed a little above the subfloor. If hardwood flooring is used, the base is installed after the wood flooring is in place.
Ceiling Trim Molding
Ceiling trim, also called crown molding, is placed at the top of walls and helps provide visual separation between the wall and ceiling. Oftentimes, crown molding can be elaborate in detail to give the room a more elegant feel.
Crown molding comes in various profiles, from simple to highly ornate. In addition to its profile and level of ornamentation, color can be used to accent the wall further.
From a design perspective, crown molding that is more ornate and elaborate works best on rooms with high ceilings. In rooms that have lower ceilings, a simple profile and a more narrow dimension is more effective.
Wall Trim Molding
Trim installed anywhere on walls other than at openings or at the corners of ceilings or floors falls under the category of wall trim. Because it is placed directly on walls, wall trim is generally more aesthetic than functional.
One exception to this is the chair rail, and to some degree the wainscoting, which helps protect the wall from damage. As their name would suggest, chair rails were traditionally used to prevent damage to walls from chairs and other types of furniture.
Wainscoting is paneling installed underneath chair rails and is usually more decorative and elaborate in detail. Wainscoting helps to break up the wall and add some visual interest and proportion at the bottom portion of the wall.
Picture rails are another type of wall trim used to provide a horizontal edge on which paintings or pictures can be hung from. A similar type of trim is the wall frame, which is usually comprised of four trim pieces forming a square or rectangular shape. Wall frames are for the most part decorative.
Common Trim Materials
Trim is also often classified based on the material it is made from. While wood has traditionally been used and is still one of the most widely used trim materials, today there are many other options to choose from.
Which type of trim material you use can vary depending on the budget you have in mind and the type of finish you want to achieve. If, for example, you want a more natural finish or want to stain the trim, then bare wood is your best option.
On the other hand, if you are planning to paint the trim, looking at primed wood or other options that require less time and labor to install may make sense. Let’s look at the most common materials used for trim and molding.
If you want your trim or molding to reveal the natural look of wood, then bare wood is your best option. It will allow you to stain the trim and retain the natural characteristics of wood.
Bare wood trim is available in a wide range of wood species, including poplar, pine, fir, oak, and aspen. Each has its own unique appearance and can vary in terms of ease of installation.
Primed wood is natural wood that has been already primed, making installation quicker since it doesn’t require the initial step of priming the wood surface.
If you are planning to paint the trim, then it makes sense to use primed wood to make installation more efficient and save time. Primed wood is generally made from less expensive wood, making it a less expensive option.
A less expensive alternative to natural wood is wood composite. Made from wood fibers bound together with resins and finished with wax.
Wood composite trim can be factory-primed and has a similar appearance to wood. It can be used in both interior or exterior applications.
Medium-density fiberboard (MDF) is often used for trim in interior settings. The least expensive option, MDF can be painted to achieve the desired finish.
However, it does not perform well in moist or damp spaces and should not be used in exterior settings. It can work in permanently dry spaces but is not recommended on floors or around windows and exterior doors due to moisture.
Another inexpensive material that can be used for trim is polystyrene. It is made from rigid polystyrene foam and can be painted with water-based paint. It tends to be less durable than other trim materials.
However, polystyrene trim does have a few advantages. It is very light and easy to cut, even with a knife, and can be installed with a back adhesive, eliminating the need for nailing to the wall surface.
If you are looking for a more durable but less expensive alternative to wood, polyurethane can be a good option. It usually comes ready to be painted.
Polyurethane can also be sawcut and nailed to the wall surface the same way wood can. Overall, polyurethane handles much like wood but is lighter, making it easier to work with.
PVC trim is typically used on exterior applications. It holds up well to moisture as well as direct sunlight. This makes it a good option for outdoor settings.
PVC trim cuts almost like wood. In terms of cost, it is similar to knot-free wood. PVC comes is an array of colors so it doesn’t require painting. It can be used indoors as well as outdoors.
Trim is characterized by both the placement and the material it is made from. Molding, a more elaborate type of trim, is further distinguished by its unique profile and level of ornamentation.
The range of materials used for trim can vary greatly, each with its advantages and disadvantages. While wood has traditionally been the most commonly used material for trim and molding applications, today there is an array of modern materials that can also be used.
Selecting the best material for your project depends on the look you are trying to achieve, the budget you have in mind, whether the trim is being installed on the interior or exterior of your home, and how labor-intensive you are willing to make the installation.
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