DIY custom rounded or bullnose corners for baseboards

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Today we are talking about baseboards! I just replaced all of my floors with gorgeous Hewn Stoneform Flooring, so of course I had to update my baseboards at the same time! My home was built when rounded edges were all the rage and I have soft corners throughout.

The theory is that rounded edges are more aesthetically pleasing and allow our eyes to easily follow the curves in the room, because curves are a more natural path for the head and eyes to follow. Sharp square corners, on the other hand, throw your eyes off! The lines changing direction abruptly is more jarring and not as pleasant to process. I think I agree! I like the modern look of a round corner, but they do create extra challenges when it comes to home renovation projects. 

It’s a good thing I love a challenge! 

This baseboard project had a LOT of corners, and I needed a good solution that would be easy enough to do and also create a look I was happy with. The old baseboards used a round baseboard cap designed specifically for this purpose. Replacing them with another cap would definitely be the easiest solution, but honestly I just don’t like how it looks. The corner caps are also very expensive, and I wanted a cheaper solution.

Old Baseboards with rounded cap

Instead, I decided to do bullnose corners! If you’re not sure what those are, just stick with me, and I will explain everything.  

Materials & tools you will need to DIY round corners for your new baseboard trim

Prefer video? Watch my step by step installation process HERE.

What are rounded corners called for walls and baseboards?

Basically, a bullnose is what is created when you cut three pieces of straight baseboard at certain angles so that the edges will meet properly around the corner. This is instead of an actual rounded cap, so the look is very different! I think the clean, straight lines a bullnose creates are perfect for my style and the rest of the house.

What angle do you cut baseboards?

Here’s a bit of math to help you understand what I mean.  A true corner is a 90-degree angle. In order to create a 90-degree angle with baseboards you would need to cut 2 boards each at 45-degrees [45+45=90]. Obviously, with a rounded corner you cannot just make a 45-degree cut on two boards, or you would end up with a giant hole between your wall and baseboards. So instead, we actually need to use 5 pieces of wood to create two separate 45 degree angles. Your angles always need to add up to that 90-degrees.

By using five pieces of wood and cutting all four edges at 22.5 degrees, you get 90 degrees where the edges all meet up properly to go around the corner.  [(22.5+22.5) + (22.5+22.5) = 90]

Standard Corner Angle: 45 + 45 = 90
Bullnose Corner Angle: [(22.5+22.5) + (22.5+22.5) = 90]

Center Width Measurement
Angle Cut Measurement

How do you cut baseboards with rounded corners?

My miter saw has the angles marked on it, which is the easy way to make 22.5 degree angled cuts for your trim pieces! I find that it is easiest to calculate how many corners you will have for your baseboard project and just cut all the corner pieces at once, since once you figure out the size of your middle piece they should (fingers crossed!) be all the same size. Making cuts in bulk will save you a lot of time! 

The center piece of wood that sits on the rounded part of the wall is the trickiest piece to cut, because as well as the angles you also need to get the width right. You will need to measure the piece of the wall where that piece will sit to make sure it is wide enough that its edges will meet the edges of the two pieces of baseboard on either side of the corner. Typically it will be somewhere between ¾” and  ⅝” wide.

Installing DIY bullnose corners for baseboard

Once I had all the corner pieces cut, I then had to cut my last two side boards the proper length for each corner. Then I used painter’s tape to tape them together in place around the corner to install them. This way there were no gaps or movement when I installed them properly. Once the taped boards were in place, I used my nail gun to install all five pieces, and then removed the tape.  

Of course, once baseboards are installed we know that’s not the end of it! The first thing I did to finish them was apply wood filler to all the cracks where the joints meet around the corners. 

Wood Filler Vs Caulk

A common question is when to use wood filler vs. caulk. Wood filler is great to fill nail holes or where two pieces of wood meet and I want it to look like a single piece (another option is to use spackle!). I use caulk where wood meets another product (like the wall), or for the inside corner seams of shelves and cabinets. 

Once the corner pieces are all wood filled and sanded, it’s time to caulk! I caulked the top of every baseboard where it met the wall.

I honestly hate caulking so much, but this battery powered caulk gun makes it go so much faster, and doesn’t hurt my hand!

There you go! Step by step instructions for how to create bullnose baseboard corners and go around rounded corners with baseboard like a pro. I love how it turned out! The clean modern lines suit my style better than the old rounded cap, and it’s always good to learn something new. How did you solve the round wall corner problem in your house? Tag me @designingparkside, I would love to see! 

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