Hints on Trimming With MDF


Medium-density fiberboard, often known as MDF, is widely used for interior trim by builders due to its lower cost and the fact that it can be worked in the same manner as wood. Since MDF does not have a grain and its natural surface, which ranges from tan to light brown, is not very attractive, it is often painted. The vast majority of lumberyards have MDF trim boards that have already been cut into a variety of profiles, and it is not difficult to produce these boards locally. In most cases, pre-milled trim boards have already been primed and are prepared to receive a finish coat.

Pre-Milled MDF Trim

The vast majority of MDF trim sold at lumberyards is custom milled for one of many applications, and most of it is sold there. The width of the door and window casings is three inches, and they are bevelled. It is recommended that you place them such that the side of the bevel with the thinner profile is facing away from the wall. There is a wide range of widths available for baseboards. They differ from casings in that they do not have bevelled edges and often have a rounded top edge. In addition, for practical uses, such as concealing seams between wall panels and trimming built-in cabinets and shelving, trim boards are available. These boards have two rounded corners and a face that is either 2 inches, 3 inches, or 4 inches wide.

Fabricating MDF Trim

Using a table saw and a rotary tool equipped with a routing attachment, you may cut and shape your own MDF trim; but, the high glue concentration of the material might be difficult for your blades to work with. Blades with carbide tips will dull more slowly and reduce the amount of tear-out and chipping that occurs. MDF is difficult to sand due to the high glue concentration it has; thus, saw cuts and router passes should be as clean as is feasible. Using power tools to work MDF generates more dust than working with wood does, therefore it is recommended by Family Handyman that you use a dust mask and often vacuum the area where you are working to keep it clean.

Installation of MDF Trim

When attaching MDF trim, a nail gun is used by many builders. When compared to hand-nailing, this method is not only quicker, but there is also a lower risk of the material chipping or separating. When subjected to stress, MDF practically pulverises, making repairs impossible. This is in contrast to wood and plywood, both of which split along a shear line. By drilling a pilot hole for each nail prior to attaching MDF using a hammer and nails, you may prevent chips and fractures from occurring in the MDF. Because the edges of the boards can become loose even if pilot holes are drilled, fasteners should never be placed any closer than half an inch from the board’s edge.

Painting and Caulking

When you buy MDF at the store, it is often already primed, but when you manufacture your own, it is recommended that you prime it beforehand before installing it. Some builders even paint a final coat on the finished product. When you seal the margins of painting pre primed MDF trim boards with caulk, as is the typical procedure, you should apply the caulk to primed MDF and paint after the caulk has dried. Caulk should be applied to primed MDF before painting. If you pre-paint the boards, you won’t need to paint the caulk since you may use a caulk that is the same colour as the wall or trim paint instead.

Filling the Nail Holes

Following the installation of the insulation, you will need to patch up any nail holes in the MDF trim. The publication Handyman’s World recommends that you make use of a wood filler that is solvent-based. Put some wood filler on a putty knife, and then use the knife to spread it over the nail holes in the wood. After you have ensured that any excess has been removed, you should wait for the filler to thoroughly dry before proceeding. You will need to paint over the filler if the colour of the filler does not correspond to the colour of the trim.