How to Install Horizontal Blinds

Horizonal blinds can have slats made of aluminum, vinyl, solid wood or faux wood. But that’s not the only customization of your blinds. You also get to choose how to hang them. How you install horizontal blinds determines the look of the window.

Horizontal window blinds can be installed two basic ways: inside or outside the window opening. An inside mount will hang inside the window frame. An outside mount attaches to the wall or window trim, depending on how much coverage you’d like.

You’ll need to choose the mount type before getting into further customizations. When deciding between an outside mount or an inside mount for horizontal blinds, here are a few things to consider.

Outside mount horizontal blinds tend to:

• Make windows look larger.
• Keep out more light.
• Make ceilings appear taller.
• Cover shallow windows that can’t fit inside mount blinds.
• Hang freely over handles or security sensors.

Inside mount horizontal blinds are known to:

• Give a sleek look to windows.
• Let in more light around the edges.
• Show off window trim.
• Leave room to hang curtains or drapes.

If you’re unsure about which mount to choose, begin by measuring your windows. Use a metal tape measure, not a cloth measuring tape, to get the most accurate numbers. The shape of the windows might narrow down your options too.

Inside mount is recommended, if possible. However, an inside mount might not be an option if your windows have a handle or crank on the sill, or if they’re not square. Those types of windows often require outside mount horizontal blinds. You might also need an extension bracket to allow the blinds to hang smoothly.

Measure the height, width and depth of the window. For window measurements, width is always listed first. Measure to the nearest 1/8 inch, but don’t round.

• For the width, use your measuring tape to measure across the window at the top, middle and bottom.
• Measure the height from the top down on the left, middle and right of the window.
• The depth is the distance from the window glass to the edge of the moulding or window trim.

In general, get the right window measurements for blinds as follows:

• Width: Go with the narrowest width of the three for horizontal blinds.
• Height: Choose the tallest height.
• Depth: Measure at the deepest section of the window. Note obstructions like handles.

You’ll also want to see if the window is square:

• Measure on the diagonal from top left to bottom right.
• Then, do the same from the top right to bottom left corners.

If both diagonal measurement numbers match or differ by 1/4 inches or less, your window is square. Inside mount horizontal blinds should fit just fine. When your windows are off square, outside mount blinds are a better bet.

Once you’ve gotten your new blinds, it’s time to install them. You’re going to need your ladder to reach the top of the wooden window frame. Here’s how to hang horizontal blinds with an inside mount.

First, install the brackets within the window frame:

• Gather the end brackets and a pencil. Climb your ladder.
• Hold the end brackets in place, exactly where you want them. They should be snug into the top corners of the window.
• Using a pencil, trace the openings to mark where the pilot screws go. Remove the bracket.
• Follow the same tracing procedure for the center bracket if you have one.
• Use a level to check that each set of holes is even.
• Using a drill with a 1/16-inch bit, drill the pilot holes within the holes you traced. You want the holes smaller than the screws you’ll use.
• Line up the bracket with the pilot holes.
• With the provided screws and your drill, fasten the bracket to the window frame. You may need to use a screwdriver if the angle is difficult to reach with a drill.
• Repeat on the other side with the second bracket.

Now install the headrail:

• Take the headrail and attach the plastic valance clips evenly along the top.
• While standing on your ladder, reach up to fit the headrail onto the brackets.
• Once the rail fits into place, snap the brackets closed. The top portion should fold down and fasten shut.
• If blinds hang long, check the directions for removing some of the slats from the bottom.
• Attach the wand to the hook on the headrail if you’ve got one.

After the headrail is attached, add the valance:

• Slide the valance onto to the valance clips.
• It covers the headrail, so you won’t see it after it’s installed.

Assure your blinds work by using the wand to raise and lower them.

With horizontal blinds with an outside mount, you’ll be drilling into the wall or window frame. If possible, keep both wood screws and drywall anchors on hand. That way, you’re prepared for both situations. Make sure you have drywall anchors if you’re fastening brackets to the wall.

If you’re drilling into wood like the window frame, trim or a stud, you won’t need the anchors. Should you be unsure if you’re on a stud, err on the side of caution. Use an anchor.

Tip: If you meet resistance about a 1/2 inch in while you’re drilling, that’s likely the stud. You can check for a swirl of yellow pine sawdust on the end of your drill bit. Sawdust means that you hit wood.

Install the brackets outside the window frame. You may need extender brackets if you’re outside the window casing. To hang outside mount horizontal blinds, follow these steps:

• Gather the end brackets and climb your ladder.
• Hold the first end bracket in place, exactly where you want it.
• Using a pencil, trace the openings to mark where the pilot screws go. Remove the bracket.
• Measure outward from your frame to your first bracket marking and note the angle and distance. If you can reach, measure downward from your ceiling to the top of your bracket and record that number.
• Use a long level to check that the second bracket is even with the first. This is important, especially if your blinds will go above and outside of your window frame.
• Using the measurements from the first bracket as a guide, mirror that distance and angle for the other bracket. A carpenter’s square may prove useful if the bracket is 45 degrees from the corner of the window frame.
• Mark the holes for your second bracket.
• Follow the same tracing procedure for the center bracket if you have one. It should be off-center just a bit. Make sure it’s the same distance from the ceiling as the other brackets.
• Using a drill with an appropriate bit, drill the pilot holes in the holes you traced. Carefully tap in the drywall anchors with a hammer.
• Line up your bracket with the drywall anchors or pilot holes.
• With the provided screws and your power drill, fasten the bracket to the window frame. You might need a screwdriver if the angle is tough to reach with a drill.
• Repeat for the remaining brackets.

Now it’s time for the headrail:

• Take the headrail and attach the plastic valance clips evenly along the top.
• While standing on your ladder, reach up to fit the headrail onto the brackets.
• Once the rail fits into place, snap the brackets closed. The top portion should fold down and fasten shut.
• If you’ve got extender pieces so your blinds clear any hardware, attach them. Take the L-shaped pieces and snap them onto each end of the headrail.
• If the blinds hang long, check the directions for removing some of the slats from the bottom.
• Attach the wand to the hook on the headrail if you’ve got one.

Finish with the valance:

• Slide the valance onto to the valance clips, top part first.
• Then snap on the bottom part, covering the headrail.

Test your blinds to see that they raise and lower correctly.

There's a lot to consider when learning how to install horizontal blinds. Keep these tips in mind to make the job easier.

Long Blinds: The longer the blinds are, the harder they are to raise and lower. For large windows, consider installing several rows of shorter blinds rather than one long one.

Many Identical Windows: Although your windows may appear to be identical, you still need to measure them individually. Small variations in size are common. Furthermore, few windows are perfectly squared up, so measure your diagonals as described above.

Check Your Work: Double or triple check your measurements. The most accurate numbers give the most accurate fit. Make sure width and height are marked clearly and not reversed.

Safety: If you plan to hang aluminum blinds in a nursery, make sure the paint on them is certified lead-free by the manufacturer.