Finish carpenters and diy'ers can alleviate the need to cut and miter corner baseboard joints by making plinth blocks on the fly. A plinth block is simply a corner block that takes the place of the baseboard to baseboard juncture. This applies to both inside and outside corners. Making your own plinth blocks can be time consuming, but offers the choice to bring a custom look to the finished job.
These plinth blocks are also used where floor transitions take place and floor levels change. For floor transitions, simple easily made blocks look and work fine, no fancy stuff needed.
For starters, baseboard plinth blocks are a piece of wood that is about the same height of the baseboard you are using. So when you make your own, you need to be aware of the baseboard height. If you have access to a wood lathe, you can produce some extremely ornate, intricate corner blocks fairly easily. Otherwise, you may just cut square blocks to fit the baseboard material and fasten them into the corners.
Many finish carpenters opt to purchase plinth blocks as it is inherently easier and faster. This leads to the design limitations that are available to you. If you or your customer is looking for colonial design corner blocks and the local stores dont have it, you could end up traveling to find them. The alternative is making plinth blocks on site or ahead of time.
The baseboard plinth blocks act as the corner piece of the wall. The baseboard is cut to fit in between the two corner plinths with a flush cut on each end. There is no need to miter the ends at 45 degrees.
Some walls have corners that are oddly shaped. We have all run into rounded corners, uneven corners or specialty bullnose corners. All of these can be challenging to trim properly and most times, the baseboard can have gaps along the wall or at the corners that will not be taken care of by over nailing or adding some silicone sealant to the job. When this is the case, making or buying plinth blocks to fit is the method of necessity.
Another benefit of using baseboard plinth blocks is where the wall is longer than the baseboard materials you are using. Baseboards are purchased in lengths up to twenty feet. If you are trimming a wall that is longer than that, you will need to butt a second piece of baseboard material in the middle of the wall. Making plinth blocks that can be used in the center of the wall give a nice, custom look to the finished trim job. Just be sure to place the plinth blocks in the center of the wall for an even, uniform look.