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Add A Plinth Block to Door Trim for a Finished Look

Stumped on how to transition between your baseboards and door trim? Try a plinth block! This tutorial will show you how to install them for a finished look.

door trim before and after installing a plinth block

Adding new doors to an old house can be a challenge, especially matching the trim. A plinth block can be the perfect solution for these transitions.

This little piece of molding can completely change the look of your baseboards and door casings. Check out all these different ways you can use plinth blocks in your home!

In this article, I'll show you how to install a plinth block to fix awkward transitions between the door trim and the baseboards.

As part of our deck remodel, we turned a window into a sliding glass door. Our contractor specialized in exteriors, which meant the work done on the interior door trim wasn't exactly stellar.

improperly installed door trim with awkward baseboard transition

Yuck! Now the edge of the baseboard was exposed, as well as the slightly damaged hardwood floor. The entire transition just looked wrong! I decided to take matters into my own hands and fix it myself.

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Straightening the Threshold

Not only was the door trim a mess, but the threshold had some issues as well. Something must have warped, because there was a ⅜" gap in the center between the back edge of the threshold and the door.

The gap was too big to fill in with clear caulk, so it was just a great place for dirt and crumbs to get trapped.

gap between threshold and sliding glass door frame

Luckily, the threshold hadn't been nailed down yet, so I brought it down to the workshop to give it a little trim. I used a block plane to shave off a little bit from each end of the back edge, leaving the center intact.

shaving the edge of the door threshold with a block plane

It took a few trips back and forth to test the fit before I finally got the threshold to lie flat against the new door. Once the gap was gone, I nailed it into place using a brad nailer.

Nailing down the threshold with a cordless brad nailer

Installing the Plinth Block

Next, I wanted to find a way to improve the transition between the original baseboards and the new door trim.

I carefully removed the door trim so it could be reused. Run a box cutter along the caulk line so you can remove the trim without ruining your drywall.

I found these plinth blocks among the many options on the Home Depot website. You can also find other styles of plinth blocks that may work better with your decor.

The dimensions of this particular plinth block fit the gap perfectly, and it was a similar style to the original trim. I gave each plinth block a couple coats of our trim paint color, then nailed them in place.

plinth block nailed to the bottom of the wall

After setting the plinth block in place, I put up the rest of the trim, following this great video tutorial from the Family Handyman. I had to improvise a bit when it came to installing the top piece, because it was long and floppy and no one was home to help.

Luckily, I could just open the door and clamp it in place from the outside. It was like having an extra set of hands!

clamps holding the trim above the door in place

I reused the mitered end of the trim done by the contractor, so no mitered cuts were necessary. I just marked where the plinth block started and cut the bottom to fit.

Then I lined up the outer edge of the trim with the outer edge of the plinth block, and nailed it into place.

plinth block with door trim installed above it

To finish it up, I spackled the nail holes, caulked all the edges, then painted everything the same trim color.

plinth block seamlessly transitions from door trim to baseboards

I'm glad I put the extra time and effort into finishing the trim properly. A sloppy detail like that drives me crazy! It was a simple, inexpensive solution that made the whole project come together.

sliding glass door with new plinth blocks installed at bottom of trim


Saturday 4th of March 2017

So I learned something new today.....I have plinth block in my house and didn't know it. This turned out great and a clever solution to your problem.


Thursday 9th of February 2017

I am new here. Wanted to tell you "You are Wonderful" and I love your site. I don't have the tools or the know-how to install plinth blocks but love seeing what you have done!!!! Thank you for all the fun information!


Thursday 9th of February 2017

Aw, you're so sweet! Thanks for your kind words!


Thursday 9th of February 2017

Brilliant! It looks so good - like it was there from the get-go!!!


Wednesday 18th of January 2017

Looks great! Our 128-year-old house came with plinths but I had no idea you could buy them on Amazon.

Angie ~ ambient wares

Tuesday 10th of January 2017

So clever and it looks spectacular!

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