The Difference Between Inside and Outside Mount Blinds

Measuring for inside mount depth
BY BLINDSTER | August 28, 2014
September 29, 2023

How should you mount your window blinds? Should they be on the inside of your window's casing, or outside of it?

That decision is up to you.

For now, we'll give you some tips so you know the pros and cons of each.

Why Mount Your Blinds Inside the Window Frame?

When you do this, your blinds are recessed and contained inside of the window’s casing. It’s the most popular way of mounting blinds. That’s because when you mount your blinds this way, your windows get a clean, finished look. And if you have molding running around the edges or window casing that you want to show off, inside mount blinds make that possible.

Inside mount blinds also make sense if you don’t want your blinds to catch on your drapes. Their one drawback is you can’t use them if:

  • The depth between the glass and the end of the window casing is less than ¾ inch.  If you have less than 3 inches of depth the blinds and valance may extend outside the window opening they are open.
  • Obstructions like window cranks and alarm sensors make it impossible to install and use them

If you are the one installing them, make sure you order using the window opening width (smallest of the width measurements at the top, middle, and bottom of the window).  The factory will take a width deduction (varies by product) so that the blinds will fit inside the window and move freely.  There may be a smidgeon of light showing on each side of the blind.

Why Use Outside Mount Window Blinds?

These window blinds are generally less popular than inside mount blinds. You install them by fastening them either to your window’s upper molding, the wall just above it, the ceiling or out to the side of the window.

Outside mount window blinds may make sense for you because:

  • You have unsightly window casing, molding, or glass you want to hide (much cheaper than installing an entirely new window)
  • You want to block more light than inside mount blinds block by covering the entire window opening
  • Your window casing is either too shallow or has obstructions in the way of installing inside mount blinds
  • You have doors you want to cover – they almost never have enough space for inside mount blinds
  • You like doing everything in a unique way

Because they are not protected by the window casing, one of the downfalls of outside mount window blinds is they can be damaged easier if they are bumped or jostled.

A Word of Warning!

With outside mount blinds, you have a greater margin for measurement error because there’s more room to mount them. We usually recommend that you add either 3 inches to the height of your window opening or 2 inches to the width (or both) to completely cover the window opening.  However, you need to make sure you have a flat space large enough to install the brackets (size varies by product ranting from 1 inch to 3 inches).

You still need to have accurate measurements with both types of blinds. However, width measurements are more critical with inside mount blinds because you have less room for error inside the window’s frame.

You should always aim to be very precise with your measurements because the more precise you are, the more light your blinds block out. Be sure to use a metal tape measure.  If you’re uncomfortable taking measurements on your own, you can always have a professional help you.

Hopefully that sheds some light on the issue of inside and outside mount blinds!

Visit Blindster.com when you're ready to start shopping for new window blinds, shades or shutters!