How to treat windows with bullnose corners

Yasmeen 12/31/2019 11:10:15 AM Buying and Fitting Shutters
DIY plantation shutters are quite straightforward to measure and install. If your windows have bullnose corners, there are a couple of points to consider when measuring and choosing your shutter frame.


Measuring for shutters for bullnose windows

When measuring for inside mount shutters for bullnose windows, you will want to measure at the narrowest part of the recess.

This means measuring at the flat inside portion of the recess. If you measure at the front of the opening, the rounded corner can skew your measurements and the shutter might be too large to fit inside of the recess.

If you are measuring for outside mount shutters for bullnose windows, you will want to measure to the widest part of the rounded edge, where it starts to turn flat. Then, you want to add the width of the shutter frame to that measurement. This will ensure that the entire shutter frame sits on the flat surface of the wall. 

Visit our measuring guides for more detailed measuring instructions for both inside and outside mount.

Choosing a shutter frame for bullnose windows

For inside mount you will have a choice of an L-Frame or a Z-Frame.

An L-Frame will fit completely inside the recess of the window. If you mount the L-Frame flush with the wall, you may have to caulk to fill in any potential gaps between the square shutter frame and the rounded corner of the window.

You can push the L-Frame back closer to the glass, so it is flush with the flat inner portion of the recess. Keep in mind that this may prevent your shutter panels from opening a full 180 degrees.

A Z-Frame has an overlapping lip with a trim that surrounds your window opening. If you choose a wide enough Z-Frame, this will cover the rounded edge and hide any gaps from being visible.

The decorative lip of the Z-Frame will cover the rounded corner and hide any gaps. 

Keep in mind that with a Z-Frame, the frame is hugging the rounded corner, so you may have to drill your frame screws in at an angle to make contact with the flat surface. We advise requesting no pre-drilled holes in your shutter frame if you opt for a Z-Frame on a bullnose window.

Inside mount framing options for bullnose windows

For outside mount you will have a choice of an L-Frame or a Deco Frame. Both will work just as well and hide the rounded edge when your shutter panels are closed. It is important to be sure you measure for the shutter frame to sit fully outside of the rounded edge.

 Many of the pictures you will find in our galleries showcase an outside mount L-Frame.

Check out the Design section of our video library for more help choosing a frame.

It will be very helpful to print the templates from our outside mount measuring guide to help you position the frame on the flat surface and take precise measurements.

Bullnose corners generally are reinforced with metal and may require you to purchase your own screws made to penetrate metal, if you are drilling into the rounded area.

Though you may consider your windows to be odd-shaped or awkward, trust us, we have seen them all! There is a straightforward solution for each unique case. Bullnose corners are no exception. Send a picture of your window to our shutter experts at for advice on measuring or designing your shutters.


This post was brought to you by Yasmeen, one of The Shutter Store USA's experienced shutter consultants. Contact our team today for advice on your shutters. We're here to help!