Every blind, shade, and shutter I sell gets installed one of two ways. Inside the window frame, tucked into the opening, or outside the frame, mounted to the wall or trim above it. It sounds like a small technical detail, and it completely changes how the finished window looks and works.
Homeowners rarely think about mount type until I bring it up at the kitchen table, and it is one of the decisions I spend the most time on during an estimate. The right call depends on your window depth, your trim, your light and privacy needs, and what the room is doing. Here is how I think it through, window by window.
What each mount means
An inside mount installs the treatment within the window opening itself. The headrail attaches to the top of the frame inside the recess, and the blind or shade hangs entirely inside that box, flush with or just behind the wall surface. Your trim stays fully visible around it.
An outside mount attaches to the wall or the trim above the opening. The treatment hangs in front of the window rather than inside it, and it usually extends a few inches past the opening on the sides and bottom. Done right, it reads the way drapery does, covering the window and a bit of the wall around it.
Neither one is the upgrade and neither is the compromise. They are different tools. The same shade can look built-in and tailored as an inside mount, or larger and more dramatic as an outside mount. What decides it is the window itself, which is why I check every opening before recommending either one.
The clean built-in look of inside mount
Inside mount is what most people picture when they imagine finished window treatments. The shade sits inside the opening like it grew there, the lines are crisp, and your casing and trim stay on display. If your home has the wide, detailed woodwork you find in older Des Moines neighborhoods, hiding it behind an outside mount would be a real shame.
Inside mounts also keep things tidy in function, not just looks. The treatment does not stick out into the room, so it never catches a shoulder in a hallway or blocks a door swing. Stacked side by side across a bank of windows, inside mounts give you a clean rhythm of identical recessed shades.
The tradeoff is light. Because the shade must clear the inside of the frame, there is a small gap at each edge, and a little daylight sneaks around it. For most rooms that is nothing. For a bedroom that needs true darkness, it matters, and we handle it differently.
When outside mount is the smarter call
Outside mount is the problem solver. Shallow window frame that will not swallow a shade? Mount outside. Crank handles, alarm sensors, or a lock sticking into the opening? Outside. A window that is out of square by half an inch after ninety years of settling? An outside mount covers the crookedness instead of showcasing it.
It is also the light control champion. Because the fabric overlaps the opening on every side, outside mounts block the edge glow that inside mounts allow. For blackout bedrooms and media rooms, an outside mounted shade with a few inches of overlap is the single most effective thing you can do short of adding side channels.
And there is a design trick hiding here. Mounting a treatment high above the frame and wider than the glass makes a small window look substantially bigger. I use that one constantly in older homes where the windows are modest but the ceilings are tall. Nobody ever guesses the glass is smaller than the shade.
Depth, trim, and obstacles
The window itself gets a vote, and sometimes a veto. Every treatment needs a minimum depth of flat mounting surface inside the opening, and some need considerably more for the shade to sit fully recessed. Newer construction usually has generous depth. Older homes, storm windows, and replacement windows often do not, and a shade that sticks halfway out of a shallow opening loses the clean look that made inside mount appealing in the first place.
Then come the obstructions. Window cranks, tilt latches, security sensors, and meeting rails all live inside that opening, and the treatment has to clear them through its full travel. I have seen beautiful shades rendered useless because a crank handle stopped them eight inches above the sill.
Trim finishes the checklist. Outside mounts need enough flat casing or wall space to anchor into, and ornate or angled trim can complicate that. None of this is a problem when it is caught during measuring. All of it is a problem after.
How mounts change measuring
Inside and outside mounts are measured completely differently, and mixing up the rules is the most common way DIY orders go wrong. For inside mounts, you measure the exact opening in three places, top, middle, and bottom for width, then both sides and center for height. The manufacturer takes small deductions so the shade clears the frame. You never make the deduction yourself, and you always use the narrowest width, because a shade sized to the widest point will jam.
Outside mounts flip the logic. You measure the area you want covered, then add overlap on each side and above so the treatment blocks light and looks proportional on the wall. There are no factory deductions. What you specify is exactly what arrives.
Custom treatments are made to the sixteenth of an inch, and cut fabric does not get a second chance. If you want to see how the whole process runs from first call to final install, I walk through it on my how it works page.
Getting the call right the first time
Here is the honest summary. Deep openings, pretty trim, and everyday rooms lean inside mount. Shallow frames, crooked openings, blackout needs, and small windows lean outside mount. Most homes end up with a mix of both, and that is completely normal. What matters is that each window gets the right call before anything is ordered, because mount type is baked into the product itself.
This decision is exactly why I do free in-home estimates instead of quoting from photos. I check depth with a tape measure, hunt for obstructions, look at your trim, and ask how you actually use the room. Ten careful minutes at the window prevents the expensive mistakes that cannot be fixed after the order is placed.
If you are weighing options for your own windows, reach out and I will come take a look. I measure every window myself, I install every job myself, and the mount question gets answered correctly the first time, on every window in the house.
Have a question I did not cover? Call (515) 850-9700 or request your free in-home estimate and I will give you a straight answer for your exact windows.