My DIY Arched Window Coverings Look Custom (Thanks to Cardboard)

I woke up at 6:14 AM on a Sunday with a laser beam of sunlight hitting me directly in the left eye. It wasn't the main window—I had that automated with a heavy blackout shade. It was the 'architectural feature' above it: a semi-circle of glass that seemed designed specifically to ruin my sleep. Finding diy arched window coverings that don't look like a cheap paper fan from a hardware store is surprisingly difficult.

• Cardboard is your best friend for templating asymmetrical arches.
• Foam board provides a lightweight, rigid structure for fabric inserts.
• Matching the fabric to your lower shades is the key to a professional look.
• Thread or Zigbee motors are preferred for reliable smart home automation.

The Problem With Half-Moon Glass (And Why Retail Sucks)

Arched windows are beautiful until you actually have to live with them. Most off-the-shelf solutions are those pleated paper fans that you peel-and-stick to the glass. They look like a science project gone wrong, especially if you have high-end smart tech everywhere else. If you have the budget, you could just buy motorized light filtering arched cellular shades and call it a day. They work great, but they are an investment.

I wanted a diy window treatments for arched windows approach that felt permanent and intentional. My lower window has a sleek, motorized roller shade. Putting a paper fan above a $400 smart shade felt like wearing a tuxedo with flip-flops. I needed something that looked built-in, but I wasn't about to pay a custom upholstery shop $2,000 for a stationary fabric insert.

Why I Decided Against the 'High and Wide' Curtain Trick

The standard advice for arches is to hang a curtain rod six inches above the highest point of the curve. It hides the arch entirely. This works if you hate the window, but I actually like the architecture—I just hate the light leaks. In my living room, the ceiling height changes right at the edge of the window frame, so a straight rod would have looked crooked relative to the ceiling line.

By building a diy arched window treatment that fits inside the frame, I kept the clean lines of the room. It also meant I didn't have to deal with massive amounts of fabric bunching up on the sides of the window when the shades were open. I wanted the glass to be the star, not the cover-up.

The Secret Weapon: A Giant Appliance Box

Here is the reality: your arched window is not a perfect circle. Even if the builder swore it was, the drywall is slightly off. I tried measuring with a laser and a tape, but the math never quite worked. I grabbed a giant cardboard box from a new dishwasher and held it up against the glass. I traced the inner rim of the window frame with a pencil, keeping the cardboard as flat as possible.

This template is the only way to get a flush fit. I cut the cardboard and test-fitted it three times, trimming millimeters off the edges until it slid into the frame with just a tiny bit of friction. If you skip this part, your DIY project will have light gaps that scream 'amateur hour.' I learned this the hard way after my first attempt left a glowing crescent moon of light at the top.

Building the Stationary Arch Insert

Once the cardboard template was perfect, I traced it onto a sheet of half-inch foam board. It’s lighter than plywood and won't warp. I used a spray adhesive to attach a layer of thin batting, then wrapped the entire thing in the same charcoal linen fabric I used for my lower shades. I used a heavy-duty stapler on the back, pulling the fabric tight to avoid wrinkles on the curve.

To install it, I didn't even use screws. I used heavy-duty command strips and a few small finishing nails tucked into the window trim. The result is a 'plug' that looks like a custom-upholstered piece of furniture. It blocks 99% of the light and matches the lower section perfectly. If I ever need to clean the glass, I just pop the insert out.

Automating the Main Window Below

The arch is stationary, but the bottom window needs to move. I used the fabric from the arch project to custom window treatments with diy roller shades for the rectangular section. I used a Zigbee-based motor that runs at about 38dB—basically a soft hum that you barely notice over the HVAC system.

I set up an Alexa routine called 'Movie Night' that drops the lower shade to 100% and dims the Philips Hue strips to 10%. Because the arch insert is always there, the room gets pitch black instantly. Pairing the motor was easy: hold the reset button for 5 seconds until the motor jogs, then let the hub find it. I haven't had a single 'Device Unresponsive' error in six months, which is more than I can say for my old WiFi-based blinds.

The Final Cost: A Bespoke Look on a Hardware Store Budget

Total cost for the arch insert was about $45 (foam board, adhesive, and fabric). The motorized shade below was another $180 for the kit and motor. Compared to the custom quotes I got, I saved over $1,500. If you already have shades you like, you can even make your existing blinds voice controlled for under $100 using a retro-fit motor.

How do you clean the fabric on the arch?

Since it's a stationary insert, I just use a vacuum attachment with a brush once a month. If it gets really dusty, I pop the insert out of the frame and use a lint roller. It takes about thirty seconds.

Will the foam board warp in the sun?

I haven't seen any warping in a year of direct South-facing sun. The fabric and batting actually act as an insulator. If you're worried about high heat, you can use a thin sheet of Coroplast (corrugated plastic) instead of foam board.

Can I make the arch itself move?

Motorizing a curved track is a nightmare for a DIYer. It usually involves expensive specialized kits. A stationary insert for the arch combined with a motorized shade below is the most reliable and cost-effective way to get the look.