how to make a plinth blockTraditional Style

DIY for About $ (so cheap it’s not even worth calculating!)

I like to terminate most door trim moldings on top of beefy plinth blocks like these.

The plinths give the door trim something substantial to rest on, just like in Classical Greek architecture.  They also provide a place to terminate the larger baseboards I just know you’re going to install.

These plinth blocks are appropriate for traditional style moldings only, not Craftsman or Victorian — though you could make them work in some Victorian designs, we’ll get into that kind of attention to vernacular design in future posts.

Problem is, there aren’t many available plinth blocks you can just go out and buy, and half of the ones you can buy you don’t want because they’re designed for small, contractor-grade trim.

Besides, you want the versatility of making them to the exact height and thickness for whatever door trim you’re going to install on top of them.

How to Make Your Own Plinth Blocks

door trim molding architrave plinth blocks

Make your plinth blocks to the exact dimensions you need for your installation.



More about MDF-200 here >>

mdf board for home made plinth blocks

A few pieces of 1/2″ MDF board are all you need to make plenty of plinths.

All you need to make plinth blocks like these is some 1/2″ thick MDF board.  Here are two prices:

  1. if you’re installing a new 1/2″ thick baseboard at the same time you’re installing your new plinth blocks (and you should be), then you can make your plinth blocks from baseboard flat-stock, and so the cost of material is almost inconsequential.
  2. if you are installing a single door trim at a time, you can buy a 4′ x 4′ x1/2″ MDF board from Home Depot for about $12.00, from which you can make a box full of plinth blocks!  You can find these pre-cut MDF boards usually near the molding isle.

Step 1  Rip

I made these plinth blocks just under 4″ wide, so you’ll need to rip a piece of MDF board that wide.  Make them wide enough so you can shave a little off of each side to clean up the edges (Step 4).

Step 2  Stack the Flat-Stock

Using Liquid Nails for Paneling, stack two pieces of flat-stock on top of each other.  It’d be a good idea to put something heavy on top or to clamp them tightly together.

Step 3  Cut to Length

Cut your “blank” plinth blocks to the height you want (usually about 1/4″ taller than the top of your baseboard buildup) from your staked and glued together flat-stock.

plinth block blanks

These are the plinth block blanks.

Step 4  Shave

Clean up the outer edges of the blanks by shaving just a hair off each side on your table saw.

Step 5  Bevel

Put a 45 degree bevel on the inside corner of each plinth block.  I like to make the bevel a little less than 1/2″ thick so that it terminates just before the seam between the two stacked pieces of flat-stock.

how to make plinth blocks from mdf board

You can make your bevel whatever depth you like, but 1/2″ deep seems to be a pretty good depth.

Step 6  Sand and Round

Use a palm sander to sand the exposed end grains on the plinth.  Be careful not to round any of the corners too much — leave all but the two bevel edges sharp — the two bevel edges can be rounded off just a bit more than the others.

palm sander for moldings

The two bevel edges can be a little bit more rounded than the rest of the plinth edges.

Step 7  Install

I like to prime and sand plinth blocks before I install them.  If it’s an outside door you’re working on, then make sure that you prime the back of the plinth block before you install it, like I did on our kitchen porch door plinth block.

plinth block primed and installed

Note how the beveled edges are sanded a little more round than the other edges.

Step 8  Install Door Trim on Top

All that’s left to do is install the door trim on top of the plinth block.  The moding profile I used for this installation is very common and inexpensive.  You learn all about about this casing molding CA-001 here >>

diy door trim molding with plinth block

Soon I’ll be posting the installation sequence for the door surround that goes with this plinth block.  If you want to stay in the loop with these updates, then subscribe to our RSS feed or via email updates sent right to your in-box.