How to Build a Door Plinth

Definition

• Plinth blocks are rectangular pieces of wood placed at the bottom of the doorjamb on both sides of a door. The door casing butts into them on top, the baseboard butts into them on one side. The other side of the block faces the door opening. On Victorian homes they are usually ornate, with carved or profiled figures on the face. This type of block requires the use of a shaper and an experienced woodworker. Another type can be made using ordinary tools. This type has a rosette, which is a swirl cut into the top, and can be made in your own garage or shop.

Dimensions

• Plinth block dimensions are regulated by the baseboard and casing you intend on using or the existing trim. Plinth block height should be at least 1 1/2 inches to 2 inches taller than the baseboard. The block should be at least 1/2 to 1 inch wider than the door casing. The bottom hinge on the door should be above the top of the plinth block. Although this is not always possible on prehung or some older doors, that's OK; it will still work just fine. Plinth blocks should be at least 1/8 inch thicker or more than the thickness of the casing or baseboard. Typical thickness for plinth blocks is usually 1 1/4 inches to provide a lip between the baseboard and casing. The height variation between the block and the trim is to provide a reveal that makes the block appear substantial and imparts more aesthetic appeal. Standard plinth blocks that fit most existing trim are 1 1/4 inches thick, 4 1/2 inches wide and 5 inches tall.

Cut

• Use hardwood to make the plinth block. Select a board that measures 1 1/4 inches by 5 inches by at least 12 inches or more in length. The extra length is to provide you with enough length to safely cut the block off the board, and you will need at least two, anyway -- one for each side. If you're planning to do all of the doors in the home, use longer boards and cut the blocks all at the same time. For safety reasons, use a miter saw, but if you're OK with a table saw, use a miter gauge to cut the block on the table saw. Set the saw, and trim one end of the board to ensure it's square. Measure and cut the block 4 1/2 inches wide perpendicular across the grain. The block should measure 1 1/4 inches by 4 1/2 inches by 5 inches.

Rosette Vs. Shaper

• Most weekend woodworkers do not use shapers, and even if you own one, plinth blocks are difficult to run and can be dangerous -- they're just to small to run safely. This type of plinth block has the characteristic profiled top that rolls into dips and curves. Other more user-friendly plinth blocks have rosettes centered near the top. This type of block is recommended if you're making them at home. They're easier to make and safer while still imparting the look of craftsmanship. Start by purchasing a rosette cutter. This type of cutter fits on any ordinary drill press. There are different styles, select one that you prefer. Rosette blocks -- which are similar to plinth blocks but smaller, are used at the top corners on many doors. If you have them at the top of the door or plan on installing them, use the same cutter for both top and bottom rosettes.

Cut and Finish

• Install the rosette cutter in the drill press. Most rosette cutters are 2 inches in diameter. Center the block under the cutter so that it has even spaces on the top and on both sides. Clamp the block to the top of the drill press to keep it secure. Turn on the drill, and lower the cutter into the block slowly. Allow the cutter to cut the rosette shape into the wood slowly until the outline of the rosette is clear or it's defined enough for your taste. Depth is not critical, but the rosette should be clearly defined when you're finished. Turn off the drill. Remove the block. Sand the block thoroughly by hand with 100-grit sandpaper using a hand block. Use a folded piece of 180-grit sandpaper to sand the rosette smooth. Blunt the top edge of the block with the sanding block, rounding it as much as possible. It's OK to sand it completely round. Finish or paint the block to match the existing trim.