How To Hang Blinds In A Bay Window: Window Treatment Solution
Introduction
Bay windows are the architectural crown jewels of many living rooms and master bedrooms. They add significant square footage, flood the space with natural light, and offer the perfect spot for a window seat or reading nook. However, they are notoriously difficult to dress properly without professional help.
The complex angles and varying depths can make installing standard window treatments feel like a geometry test you didn’t study for. One wrong measurement often results in blinds that overlap awkwardly in the corners or leave massive gaps that ruin privacy. If you are looking for visual inspiration before tackling the math, you can find a curated Picture Gallery at the end of the blog post.
In this guide, I will walk you through the precise method interior designers use to hang blinds in bay windows. We will cover the crucial cardboard template trick, how to select the right mounting depth, and which blind styles minimize corner gaps. Let’s turn that tricky architectural feature into the highlight of your room.
The Geometry of the Bay: Inside vs. Outside Mount
Before you even touch a tape measure, you must decide on your mounting strategy. This choice dictates every subsequent step of the project.
In professional interior design, we almost exclusively use an inside mount for bay windows. An inside mount means the blinds are installed within the individual window frames or the recessed casing. This keeps the lines clean and highlights the beautiful molding that likely defines the bay.
An outside mount involves hanging the blinds on the wall above the casing or on the trim itself. While this is easier to measure, it often looks cluttered in a bay window. The headrails tend to project too far out, colliding with each other in the corners and obscuring the window’s shape.
However, there are exceptions where an outside mount is necessary. If your window frames are too shallow (less than 1 inch of depth), you may not have enough wood to screw into. In this case, mounting on the trim above is your only secure option.
Selecting the Right Blind Style for Angles
Not all blinds are created equal when it comes to angled corners. The size of the “headrail” (the top mechanical box of the blind) is the most critical factor in a bay window installation.
Roller Shades
Roller shades are often the designer’s top choice for bay windows. They typically have a very compact headrail or roller mechanism. This allows you to position the blinds closer together in the corners, minimizing the light gap.
They also offer a modern, streamlined look that doesn’t distract from the architecture. If you choose a reverse roll (where the fabric falls off the front of the roller), you can hide the roller mechanism entirely without a valance.
Cellular (Honeycomb) Shades
Cellular shades are excellent for tight bays because their headrails are usually slim. They compress into a very small stack at the top of the window when raised. This maximizes your view, which is the whole point of having a bay window.
They also provide insulation. Bay windows have more glass surface area and can make a room drafty; cellular shades trap air and regulate the temperature.
Wood and Faux Wood Blinds
These are tricky. Real wood and faux wood blinds usually require a large valance and a deep headrail (often 2.5 to 3 inches). In a tight 45-degree bay, these large headrails will collide long before the slats cover the glass.
If you are set on the look of wood slats, you must be prepared to have wider gaps in the corners. You will also need to measure with extreme precision to account for the projection of the valence.
Roman Shades
Roman shades add softness and texture, which is great for warming up a space. However, they can be bulky when raised. If your bay window has limited space above the glass, a stacked Roman shade might block significant light.
From a mounting perspective, Romans are forgiving. The fabric edges can sometimes be “trained” to touch in the corners, reducing privacy gaps better than hard slats.
The “Cardboard Template” Measuring Method
Forget standard measuring guides. When measuring for a bay window, the standard instructions will result in blinds that don’t fit. You need to account for where the headrails intersect in 3D space.
The most foolproof method to determine your width is the template technique.
Step 1: Determine Headrail Depth
Check the specifications of the blinds you intend to buy. You need the exact depth of the brackets and headrail. Let’s say it is 2.5 inches.
Step 2: Make Your Templates
Cut two strips of cardboard that are 2.5 inches wide (or whatever your headrail depth is) and about 1 foot long. These represent your blinds.
Step 3: Simulate the Installation
Place the cardboard strips on the window sill or inside the top casing where the brackets will go. Slide the strips into the corner until the front corners of the cardboard touch or overlap slightly.
Step 4: Mark the Intersection
Where the cardboard strips meet in the corner represents the furthest point your blinds can go. Mark the casing at the back edge of the cardboard. This is your measuring point.
Step 5: Measure Between Marks
Measure from that pencil mark to the next mark (or the end of the window). This gives you the precise width available for the blind, ensuring the headrails won’t clash.
Handling Light Gaps and Privacy
In any bay window with separate blinds, there will be gaps. It is physically impossible to have three separate mechanical systems touch perfectly at an angle without rubbing against each other.
The gap usually ranges from 1/2 inch to 1.5 inches depending on the headrail thickness. For living rooms, this is rarely an issue. For bedrooms or bathrooms, this can be a privacy concern.
The L-Shape Configuration
For 90-degree box bays, use a “butt-joint” alignment. One blind (usually the larger center one) runs all the way to the corner. The side blind butts up against the front of the center blind. This blocks the view from the outside but requires careful measuring.
Using Drapery Panels
My favorite designer solution for gaps is to install stationary drapery panels between the windows. If you have enough wall space between the angled windows, mount a small rod or hook and hang a narrow curtain panel. This physically covers the gap and adds vertical height to the room.
Privacy Liners
If you are using woven woods or bamboo shades, ensure they have a privacy liner. The natural gaps in the weave combined with the corner gaps can make you feel exposed at night.
Installation: Order of Operations
Once your custom blinds arrive, do not just start drilling. The order in which you install them matters significantly in a tight bay.
1. Start with the Center Blind
Always mount the large center unit first. Center it perfectly within the middle window frame. This creates your anchor point.
2. Check the Sides
Before screwing in the side brackets, hold the side blinds up (you may need a helper). visually confirm they don’t hit the center blind when raised or lowered.
3. Use Shims if Necessary
Bay windows in older homes are rarely perfectly square. If the window frame bows in the middle, your blind might scrape the glass. Keep a pack of plastic installation shims handy. You can place these behind the bracket to angle the blind slightly away from the glass.
4. Secure the Brackets
Use a magnetic drill bit holder. Space is tight in the upper corners of a bay window, and dropping screws is frustrating. A magnetic bit will save you time and sanity.
Designer’s Note: The Control Cord Strategy
Here is a detail often overlooked until it is too late: the placement of the lift cords or wands.
In a bay window, never position the lift controls in the corners where the blinds meet. If you put the controls for the center blind on the right, and the controls for the right blind on the left, you end up with a tangled mess of cords in that tight wedge.
The Rule of Thumb:
Left Blind: Controls on the Left.
Right Blind: Controls on the Right.
Center Blind: Choose the side that is easier to reach, or request a split control (lift on left, tilt on right) if available.
Better yet, choose cordless lift systems. They eliminate the visual clutter of strings hanging in your beautiful window. For large bay windows where reaching the top is difficult, motorized wands are a game-changer and have become much more affordable.
Layering: Adding Softness with Valances or Cornices
Sometimes the best way to hide the mechanics of bay window blinds is to cover the top entirely. A custom cornice board can be built to follow the angles of the wall.
This is an advanced DIY or a job for a professional upholsterer. A cornice creates a continuous visual line across the top of the bay, hiding all the gaps between the headrails.
If a hard cornice feels too heavy, consider a continuous valance. Many blind manufacturers can make a single valance with mitered corners that attaches to all three blinds. This connects them visually, making them look like one cohesive unit rather than three separate products.
Common Mistakes + Fixes
Even professionals make mistakes in bay windows. Here are the most frequent errors and how to solve them.
Mistake: Ignoring Window Handles
The Issue: You measure the depth of the window frame but forget about the crank handle for opening the casement window. The blind hits the handle and won’t close.
The Fix: Measure your depth from the tip of the handle, not the glass. If you already bought the blinds, you can buy “T-handle” replacements for casement windows which fold flatter than standard cranks.
Mistake: Measuring the Front vs. the Back
The Issue: You measured the width at the front of the window opening, but the blind is mounted at the back near the glass. In a bay window, the width at the glass is much narrower than the width at the wall.
The Fix: Always measure the width at the exact depth where the headrail will sit.
Mistake: Assuming Angles are Standard
The Issue: Assuming your bay is a perfect 45-degree angle.
The Fix: Use an angle finder tool or a sliding bevel gauge. Or, simply rely on the cardboard template method, which works regardless of the specific angle.
What I’d Do in a Real Project
If I were designing a bay window for a client today, here is my go-to “cheat sheet” for a successful install:
Mounting: Inside mount whenever possible to show off the trim.Product: Cordless woven wood shades with a privacy liner. The texture hides dust, and the cordless operation keeps the look clean.
Gaps: I accept the small gaps. I don’t try to force them shut. I place a floor lamp or a large plant in front of the corner gaps to distract the eye.
Hardware: I use extension brackets if the window handles protrude.
Color: I match the headrail color to the trim (usually white), not the blind material. This helps the mechanical parts disappear against the white window casing.
Final Checklist
Before you head to the store or click “purchase,” run through this list.
Depth Check: Do you have at least 2 inches of flat wood depth inside the frame?
Obstruction Check: Have you accounted for window cranks, alarm sensors, or locks?
Corner Test: Did you use the cardboard template method to find the intersection point?
Control Side: Have you specified control locations that push cords away from the corners?
Material Selection: Have you chosen a headrail style (like roller or honeycomb) that fits your depth?
Mounting Surface: Is the material you are drilling into wood, drywall, or metal lintel? (You may need special anchors).
FAQs
Can I use curtain rods in a bay window?
Yes, but you need specific hardware. Look for “bay window curtain rods” which come with flexible corner connectors (elbows). These allow the rod to bend continuously around the angles. Alternatively, use three separate tension rods if the curtains are lightweight.
What is the best blind for a rental unit with bay windows?
Paper pleated shades are a quick fix, but for a nicer look, try tension-mount cellular shades. They require no drilling. However, be aware that bay windows often have unique widths, so “off-the-shelf” tension shades might not fit perfectly.
How do I clean blinds in a deep bay window?
This is a practical concern. If the bay is deep, you can’t reach the glass easily. I recommend a vacuum cleaner with a long brush attachment. Dust the blinds regularly so you don’t have to take them down for deep cleaning, which is a hassle to reinstall.
Do I need a professional installer?
For a standard flat window, DIY is fine. For a bay window, if you are uncomfortable with geometry or using power tools at awkward angles, hiring a pro is worth the investment. The frustration saved is significant.
Conclusion
Hanging blinds in a bay window is undeniably more complex than a standard installation, but the payoff is huge. A well-dressed bay window becomes the focal point of the room, offering light control and privacy without sacrificing architectural beauty.
By using the template method and choosing the right headrail depth, you can avoid the dreaded corner collision. Take your time with the measurements—measure twice, cut once applies doubly here. With the right preparation, your bay window will look custom-designed and professionally finished.
Picture Gallery
