The Basics of Molding

Two pieces of pine wood molding sitting on a table beside a pencil.
  • 2-4 hours
  • Beginner
  • 100-500
What You'll Need
Safety glasses
Straight edge
4d finish nails
Miter saw with T-bevel

Molding is an important finishing touch for many home improvement and remodeling projects. It helps cover uneveness, crooked lines, and many other cosmetic errors a DIYer might make during a project and adds a sense of polish to the finished product. However, there's a lot more to molding than you might think. We've got you covered; the article below will help you learn about different types and materials and much more, so read on.

Molding Materials

When most people think of molding, they think of wood. This is certainly the most common material, with pine being at the top of the list. It is less expensive than other materials, and its fine grains reduce the risk of splintering, rendering it easy to manipulate. Other woods that are used to manufacture molding include not only oak and birch, but also mahogany and spruce.

In some cases, however, molding is crafted from synthetic material. These are retailed both as unfinished fixtures and as a pre-finished fixtures; pre-finished often comes designed to look like real wood. The most convenient, easy-to-use synthetic molding, and the one most homeowners prefer, is made from either particleboard or fiberboard. The drawback to this, however, is its susceptibility to water damage.

Types of Molding

While a wide abundance of finishing molds are available on the market, they generally fall into three categories of purpose. Some are used on ceilings, others are applied to the space between floors and walls, and others still are used for around doors and windows.

The three most common types are cove molding, base molding, and casing, with the most popular by far being cove molding. It is commonly used to create a conventional design theme, and it comes in a wide range of sizes, from 1/2-inch to 1/2-foot, to accommodate a range of rooms. Too-thick molding can reduce the space and make it feel cramped, so when in doubt, opt for something a little narrower. Base molding is available in a wide array of shapes and sizes. However, in most cases, you will need to also install a base cap along with this type.

Unless you are building a room with no entrance, you must also incorporate case molding into your design around doors and windows.

Working With Molding


You must always apply trim to the doors and windows in the room first. Before you start measuring and nailing, however, make sure the jambs around both of these openings are properly aligned and flush with the wall. If they stick out, plane them until the excess is gone; if they're recessed, measure the widest gap between the jamb and the wall edge and use this to cut an extension that will make up the distance. Secure this piece to the original jamb with 4d finish nails every eight to 10 inches and then plane off any excess.A window can be trimmed out either with a stool at the bottom (top), or in a picture frame style with casing on all four sides.

A window can be trimmed out either with a stool at the bottom (top), or in a picture frame style with casing on all four sides, connecting with mitered or butt-jointed corners. If you've decided to go with a window trim style that employs a stool, the first step to adding casing to the frame is to make the stool the proper length. Add a side casing to the window, lining it up with the reveal line, and mark the outside edge. Do this on both sides of the window, and then make another mark 3/4 to an inch out from each end depending on your preference. This will be the final length of your stool.

The stool will also need to be notched to fit over the side casings when it is secured. Measure the full length and width of your side casing from the jamb and mark it on the stool with a pencil and a straight edge so you know where to cut.

The rest of a window casing installation matches exactly with the method for adding trim to a door. The side casings will need to be secured before the top, so line up the molding with either the floor or the stool, and then mark your trim where it lines up with the top of the side jamb. You can either make squared or angled cuts at this joint depending on the look you want.

Glue the side casings in place before you nail. Use 4d finish nails to secure the trim to the jamb and 8d nails where attaching to the wall. Then, mark, cut, glue, and nail the head casing in place using much the same method.

Door and window casings are installed with a 1/16-inch reveal between the edge of the jamb and the casing to allow you to adjust the casing if the jamb is slightly out of plumb.

Base and Ceiling

Door and window casings are installed with a 1/16 inch reveal between the edge of the jamb and the casing, which allows you to adjust the casing if the jamb is slightly out of plumb.After you have added molding to both the doors and the windows, the next step is to apply molding to not only the base of your walls, but also around the edge of the ceiling. Start with some prep work to save yourself a little effort later. Have the home improvement center cut the molding to fit at the time of purchase, and mark the studs along the wall with a pencil.

When installing base molding, the first piece you lay will extend from the door trim, so begin by recording the distance from the door to the closest wall. Cut the molding to size with a square end, then repeat this step for the molding on the opposite side of the door. Use 6d nails to install the first run. Then, you must make a coped cut on the second strip of base molding by slicing the piece at a 45-degree angle on the end before completing the cut with a coping saw. Record the distance from the first piece of base molding to the next wall, again cutting it square at the end. Continue in the way for the rest of the corners. Use a miter saw with a T-bevel to cut an accurate 90-degree angle.

If you have an issue where your molding can't match the full length of a run, you will have to connect the two pieces in a specific manner. Place the first piece and locate the center of the closest wall stud using your initial markings. Cut the molding to align with the center of this stud. Then, secure that piece to the stud, making sure not to attach it at the cut. On the end of the other piece, cut a miter that will make the ends overlap. Use adhesive on the joint and nail the rest of the molding into place. Joints like these, called scarf joints, should always be cut and nailed directly over a stud.

Ceiling MoldingScarf joints should be cut and nailed directly over a stud.

The process for installing ceiling molding is very similar to that of base molding. The only difference is that ceiling molding is installed at a 45-degree angle rather than laying flat to the wall.

When the only corners are interior ones, all you have to do is make square cuts and cope the ends. Ceiling molding on exterior corners must be cut with a miter saw at a 45-degree angle.

Information in this article has been furnished by the National Retail Hardware Association (NRHA) and associated contributors.