Why I Never Outside-Mount 20 Inch Window Shades on Skinny Windows

I remember staring at the two vertical slivers of glass flanking my fireplace in my first fixer-upper. They were exactly 20 inches wide, and I spent three nights obsessing over whether to treat them or hide them behind furniture. I eventually made the mistake of buying standard rods that overshot the trim by four inches on each side, and the result looked like my windows were wearing an oversized, floppy hat. It was a mess. Since then, I’ve learned that 20 inch window shades require a specific kind of discipline to look intentional rather than like an afterthought.

Quick Takeaways

• Inside mounting is the only way to maintain the architectural integrity of narrow windows.
• Avoid 2-inch wood slats; they create a 'ladder' effect that feels claustrophobic.
• Precision is non-negotiable; measure to the nearest 1/8th of an inch for a snug fit.
• For French doors, use hold-down brackets to keep narrow shades from clattering against the glass.

The Curse of the 'Skinny Window'

Architects love to throw in narrow windows to fill a void—usually in a powder room, an entryway, or flanking a chimney breast. Homeowners often panic when they realize standard off-the-shelf options don't quite fit. You might be tempted to grab whatever 20 inch wide window blinds you can find at a big-box store, but if the scale is off, the whole room feels twitchy. When you're dealing with 20 in blinds, you aren't just covering glass; you're framing a very specific architectural detail.

The biggest mistake is trying to 'beef up' these windows with bulky treatments. A 20 inch window is inherently delicate. If you try to force a heavy, standard-width treatment onto it, you lose the very verticality that makes these windows interesting in the first place. I’ve seen beautiful Victorian sidelights ruined by chunky plastic headers that were never meant for such a slim profile.

Why Outside Mounting Looks Comical Here

Outside mounting a narrow shade is the visual equivalent of a giant forehead on a tiny face. Because the headrail of most 20 inch blinds has to be wider than the window to catch the wall, it creates a top-heavy silhouette. It draws the eye to the hardware rather than the view. Plus, unless you are perfectly centered, the asymmetry is glaringly obvious in a way it isn't on a standard 36-inch window.

Functionally, outside mounting these small widths is a nightmare for light control. You end up with The 2 Inch Gap Ruining Your Window Blackout Roller Blinds because the shade doesn't have enough surface area to 'hug' the wall. You get these aggressive shafts of light leaking from the sides that are impossible to block out, which is particularly annoying in a nursery or a small home office where glare hits your screen.

Getting the Inside Mount Right for 20 Inch Window Shades

If you want that crisp, high-end designer look, the shade must sit inside the casing. This honors the trim and keeps the focus on the glass. When I specify 20 inch window shades for a project, I look for a mounting depth of at least 2 inches. If your windows are shallow—common in older homes or newer builds with thin drywall—you might need to look for low-profile headers. Sleek, custom-fit Roller Shades are my go-to because they disappear when raised, leaving the window completely unobstructed.

Measurement precision is your best friend here. Don't round up. If your window is 19 and 7/8ths, order it exactly like that. A gap of even a quarter inch on a narrow window looks like a mistake. I once measured a bathroom window at exactly 20 inches, but didn't account for a slight bow in the middle of the frame. The shade stuck halfway down, and I had to hand-sand the inside of the window casing at midnight before the homeowners moved in. Learn from my sweat: measure top, middle, and bottom.

Material Matters: Why Heavy Wood Slats Look Like a Ladder

Scale is everything. If you put 2-inch wood slats on 20 inch wide blinds, the horizontal lines are so close together relative to the width that the window looks like a tiny wooden ladder. It’s too much visual noise. For these widths, I always recommend a 1-inch slat or a flat fabric shade. If you must have slats, 20 inch mini blinds in a matte finish look much more sophisticated and proportional.

Using 20 mini blinds doesn't have to look like a 90s apartment. Look for aluminum or high-quality faux wood with a 1-inch profile. This keeps the 'stack'—the amount of space the blinds take up when pulled to the top—very small. You can also find great inspiration in Why I Replaced My Metal Minis With 1 Inch Faux Wood Window Blinds, which proves that the right slat size can change the entire mood of a narrow opening.

The French Door Exception

The only time I break my 'no outside mount' rule is for French doors. Narrow glass panes on doors often lack the depth for an inside mount. In this case, you’ll want to look for 20 inch wide mini blinds that come with hold-down brackets. These are tiny clear plastic or metal clips at the bottom that keep the blinds from swinging and banging against the glass every time you open the door. It’s a small detail that saves your sanity.

For a truly clean look on doors, I often suggest motorization. Using Canisteo Motorized Dual Roller Shades Cordless Custom Double Roller Blinds allows you to ditch the dangling cords, which are especially messy on 20 blinds. It keeps the glass looking like glass, not a hardware display. When the shade is up, the motorized roll is compact enough to stay out of the way of the door handle.

Faking Width With Stationary Drapes

If you genuinely hate how skinny your window is, you can use a little design trickery. Install a sleek, functional inside-mount shade for your privacy needs. Then, hang a curtain rod that extends 10 to 12 inches past the window frame on both sides. Hang stationary drapery panels—meaning they don't actually close—so they just barely overlap the edges of the glass. This tricks the eye into thinking there is much more window hidden behind the fabric, giving a 20-inch window the presence of a 40-inch one.

FAQ

Can I use a standard 24-inch blind on a 20-inch window?

Only if you outside-mount it, but I wouldn't recommend it. It will look bulky and 'off.' It’s always worth the extra few dollars to get a custom-cut width so the hardware fits the window perfectly.

What is the best material for a 20-inch kitchen window?

Go with a moisture-resistant roller shade or a 1-inch faux wood blind. Fabric romans are beautiful but can trap grease and odors if they are too close to the range.

Do 20-inch shades come in cordless options?

Yes, and they should! Cordless is much safer and looks significantly cleaner on narrow windows where a long cord can look cluttered and out of proportion.