Introduction
Many nineteenth century homes feature elaborate molding and door casings. Sometimes these homes have rooms, like housekeepers' quarters, which feature very plain trim. Your first thought might be to replace the molding with something nicer, but there's another option. This guide will show you how to spruce up that boring trim work by adding additional molding pieces and other decorateive elements.

Plan
Begin with a simple plan. Depending on the style you're trying to achieve, you may reach your goal simply by attaching a layer of trim molding to the outer edges of existing molding pieces. You should start simply, and build up from there, adding additional layers as necessary. As you have two surrounding edges (one edge of the existing molding, and the wall), a quarter-round molding is ideal here.

Measurements
Before you cut any molding, measure the space it will fit into. There are two important tips to follow while measuring: Make sure you're at eye-level while measuring. Taking a reading from an angle, above, below, or to the sides, can result in an inaccurate measurement. It's always better to be a little long, than a little short. If you cut a piece too long, you can always go back and trim the piece to size later.

Cut the Trim
Using a miter saw, cut your pieces to length. In this case, you'll be dealing with angled cuts, called miter cuts. Since you're dealing with right angles, most of your cuts will be at a 45 degree angle (one half of a 90 degree right angle). Two 45 degree miters, when put together, will form the 90 degree angles you need. A couple of things you should keep in mind while cutting: When you need to make multiple miter cuts on a single piece of molding, you should make one cut first, and then measure from the finished cut to determine where to make the other cut. For more accurate measurements, instead of using the hook at the end of the tape measure, try using the 1 inch mark. This will be more accurate. Just remember, since you're starting your measurement at 1 inch, you need to add one inch to the length of your measurement.

Attach the Trim
Test-fit the trim by holding it in place. Check to be sure you've cut to the right length. Trim as necessary. Once the length is correct, attach the trim to the wall with nails. Since using a hammer can result in damage to the wall or molding, you should use a pneumatic nail gun to attach the molding. Remember to wear proper eye protection while operating nail guns. On air-powered nailers, uou'll also notice a powerful blast of air is driven out of the back of the gun each time you use it. This is completely normal. Using the nailer, continue to attach the remaining trim pieces.

Should I Add More?
If the trim you've added isn't enough, you may want to consider adding additional layers. For example, laying molding directly on the face of molding can create a raised look, and once finished, can still appear to be a single combined molding piece. When deciding to add additional molding, you might consider adding a plinth block. A plinth block is usually a decorative piece of molding that can look like the base of a column when used at the bottom of a door. You can also use plinth blocks as part of a fireplace surround, or in this case, at the top of a door. The additional molding will run right into the plinth block, creating a nice finished edge.

Making a Plinth Block
A plinth block can be as simple as a square or rectangular piece of wood that's at least as thick as the molding that will run into it. However, if you're going for a more decorative look, you might want to add some molding. Measure out and cut miters into some simple half-round molding, so that you'll be able to form a raised square inset from the edge of the block. Glue the molding in place. Remember to make a plinth block for each corner of the door. When your plinth blocks are complete, paint them and then nail them in place.

Adding Additional Molding
Since you have only one surrounding edge this time (the face of the original door molding), select a suitable half-round molding. Measure and cut pieces. Since there will be a plinth block on each end of these pieces, use straight cuts instead of 45 degree miters. Nail the new molding in place.

Shoe Molding
Finally, you'll want to attach some shoe molding along the edge that meets the carpet or other flooring. Simply repeat the same process as before to cut the molding to length. Then, press it down against the carpet and nail it to the wall.

Finishing Up
To fill in any gaps or cracks, you'll want to use caulking. Simply apply a thin bead and smooth with your finger. Once that's done (and has dried), apply paint as you would with any other molding.