When ordering roller shades, honeycomb blinds, or almost any other window covering, one of the first questions you'll face is whether to choose an inside mount or an outside mount. It's a decision that affects how your window looks, how much light is blocked, and how the shade interacts with your window frame and trim.
Here's a straightforward guide to understanding both options and choosing the right one for your windows.
What Is an Inside Mount?
An inside mount (sometimes called an inside recess mount) means the window covering is installed inside the window frame, sitting within the recess of the window. The headrail attaches to the top of the window opening, and the shade hangs down within the frame itself.
Inside mounts have a clean, recessed look that shows off your window frame and trim. They work well when your window frames have at least 6 to 7 centimetres of flat depth for the mounting bracket. The shade covers the glass portion of the window but not the surrounding trim, giving a built-in, architectural appearance.
The main trade-off is light leakage. Because the shade fits within the opening rather than overlapping it, some light can enter around the edges, especially at the sides. For rooms where light control is critical — like nurseries or bedrooms — inside mount shades may need to be paired with side channels or curtains to block that light gap.
What Is an Outside Mount?
An outside mount means the headrail attaches to the wall or window trim above and outside the window opening. The shade hangs over the entire window opening and extends beyond it on the sides.
Outside mounts are the better choice for light blockage. When the shade extends beyond the window on all sides, it closes off the light path more completely, which is why blackout applications almost always recommend an outside mount. Outside mounts also visually expand the window — when you extend the treatment wider and higher than the actual window, rooms feel taller and windows feel larger.
Outside mounts are also necessary when the window frame doesn't have enough depth for an inside mount bracket, or when architectural features like window sills make inside mounting impractical.
How to Decide Which Is Right for You
Start by measuring your window frame depth. If you have at least 6 to 7 centimetres of flat, unobstructed depth within the frame, an inside mount is feasible. If the depth is shallower, or if the frame has angled or decorative surfaces that prevent flat mounting, go with an outside mount.
Consider your light control needs. For bedrooms, nurseries, or media rooms where full light blockage matters, outside mount is almost always preferable. For living areas and offices where some ambient light is acceptable, either option works.
Think about window appearance. Inside mounts show off the window frame and look more refined in architectural spaces. Outside mounts are more flexible and can make small or narrow windows look larger. If you're adding curtains or drapery on top, outside mount is generally the better base layer.
Measuring for Each Mount Type
For an inside mount, measure the width of the window opening at the top, middle, and bottom — use the narrowest measurement. Measure the height on both sides and use the longer measurement. The manufacturer will typically deduct a small amount (called a deduction) to ensure the shade fits within the opening without rubbing.
For an outside mount, measure the area you want to cover. Most recommendations suggest adding 7 to 10 centimetres beyond the window opening on each side, and mounting the headrail 7 to 10 centimetres above the window frame. This ensures good light coverage and makes the window feel larger.
Frequently Asked Questions
Can I do an inside mount if my windows have handles or cranks?
It depends on the placement. If the handle or crank mechanism sits within the path of the shade, the shade may bind or not operate smoothly. In these cases, an outside mount is the safer choice.
Is outside mount always better for blackout shades?
Generally yes. An outside mount that extends beyond the window opening on all sides significantly reduces light gaps compared to an inside mount. Some inside mount blackout shades come with side channel tracks that improve light blocking, but outside mount remains the most effective option.
Does mount type affect the price of my window coverings?
Mount type itself doesn't change the price, but the measurements you provide will determine the width of the shade, which affects cost. Outside mount shades are often wider than the window opening, which may affect pricing for certain products.
Can I use both mount types in the same room?
Yes, though it can look inconsistent if all the windows are visible at once. In rooms with multiple windows of different types or sizes, mixing mount types is sometimes necessary. Keeping the treatments in the same colour and style helps maintain visual cohesion.
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