Sewing a Bay Window Seat Cushion

First of all, I have to say that I’m so glad we opted to go with the window seat in our kitchen. Since we don’t have an eat-in area (we chose to go without a table because we felt it crowded our kitchen), it’s nice to have the option for people to sit and hang out, and equally exciting… there’s lots of extra storage space in the drawers. Here’s how our window seat looks all naked without a cushion.

custom bay window seat

Custom bay window seat - before


  • Fabric (for cushion and piping)
  • Coordinating thread
  • Cable cording (for piping/trim)
  • Vanishing fabric marker
  • 2” foam (buy this with a coupon or when it’s half off! It’s not cheap!)
  • Zipper (long enough to span almost the entire length of the back of the cushion)

window seat cushion supplies

DIY window seat cushion piping

After going to Joann’s months ago to buy the supplies for this project (yep, I’m that much of a procrastinator) I decided to do the trim in a different color. So off to the store we went. I found a gray satin fabric that complimented the patterned fabric perfectly.

custom window seat piping supplies

Measure and Trim Fabric

I started off by fitting the foam to the seat. Our window seat is a trapezoid shape (not going to lie, I had to look that one up. I’m a little rusty on my geometry), so I had to cut off a triangle on each side. I triple checked that it fit the seat properly because I wasn’t about to go through this whole project for an incorrectly sized cushion.

Then I prepped my fabric. I laid it out on the table and traced the foam, leaving about an inch on all sides for seam allowance. I traced this piece for the bottom side of the cushion by laying the good sides of the fabric together… even though my cushion is symmetrical, this is just good practice. Then I trimmed the fabric for the side panels by measuring the thickness of the foam. I made sure to add the 1” seam allowance all the way around. The diagram below shows all the pieces to the cushion.

window seat cushion parts

Look how pretty this print is!

custom window seat fabric

I used my vanishing ink fabric marker to mark where to cut. Gotta love those things.

DIY window seat cushion fabric

After laying out the strip of fabric on the table, all I could think was “Wow this fabric would make a pretty table runner!” Maybe that will be in the works soon. (Hello again to my fun new chandelier drum shade!)

diy window seat cushion fabric

window seat cushion foam and fabric

Sew the Piping Trim

As always, I like to complicate my projects. I really wanted a cushion with piping on the seams, which of course I have never done before so why not try it on a cushion, which I also have never made before. Then to complicate things even further, I’m adding a zipper for easy cleaning… yep, never sewn on a zipper either. Today is all about learning new things, apparently. Let’s hope it all works out!

So now that I’ve committed myself to doing the piping, I needed to make it. I started out by trimming a long strip of fabric. I laid the cording in the center of the fabric and folded over the fabric, keeping the cord snug in the fold. I used a few pins to hold it in place. Then I used a zipper foot on my sewing machine to sew right up against the cord. This was surprisingly simple.

custom window seat cushion piping

diy window seat cushion piping trim

sewing  window seat cushion piping trim

Not sure how Kimble ended up in the photos today, but he didn’t lend a paw so he’s not getting credit for any of this project. Sorry pup.

design waffle dog

Sew the Zipper on to the Back Edge Panel

After all of the piping was finished, I moved on to the back edge panel where I wanted to hide the zipper. I cut a slit down the center of the fabric, pinned the zipper to the fabric, folding under the edges and I sewed the zipper into the fabric panel. I really had no clue what I was doing, but it worked so I must have done something correct.

UPDATE: I learned a WAY BETTER method for sewing a zipper. You can read about it here.

diy window seat cushion zipper

Sew the Zipper Edge Panel to the Front Edge Panel

After the zipper was in place, I sewed the front edge panel to the back/zipper edge panel so that I had one long edge strip that could wrap all the way around the cushion to connect the top and bottom panels.

So at this point I finished all of the piping, the edge with zipper, and the rest of the fabric is trimmed and ready for the next step.

window seat cushion

Sewing the Piping On

I pinned the piping to the sides of the top panel with the good side of the patterned fabric facing up and the ragged edges of the fabric together. The photo below shows how the two came together. I sewed it together with the zipper foot on my machine. Once the top panel was done, I did the bottom panel the same exact way. Be sure to cut little slits around your corners so the piping can bend freely around the tight corner (as shown in the photo).

sewing window seat cushion

Pin and Sew Panels Together

After both the top and bottom panels had the piping attached, I pinned the edge panel to the top panel. Then I moved onto the scary part: sewing the two together. This was actually easier than I expected. I used the edge of the piping to guide me in sewing the pieces together.

pinning window seat cushion cover

Now this is the real scary part: sewing the bottom panel to the edge panel (that was previously sewn to the top panel). This step encloses the cushion, meaning I was done afterwards. BUT not so fast, this was really tricky. At this point it’s important to make sure the edge panel is the correct thickness. You don’t want it to be too tall or the foam will wiggle around inside the cushion cover and the fabric will have too much slack. You don’t want the edges to be too short, or the cushion won’t fit at all. I have a confession to make. I spent a good 2 hours pinning, repinning, pretending to start sewing only to restart the pinning process all over, and then I realized that I needed to pull off some of the piping, reposition it and resew it. Sighhhh… this part took a while.

What I found out worked well in the end was measuring 2″ down the from the seam attaching the top panel to the edge/side piece. Then I drew a line with a pen (not my invisible fabric marker because it disappeared too quickly for this time consuming step, but the pen markings were on the back side of the fabric so all was well). This gave me a line to follow with my sewing machine. I didn’t pin this go around because… well actually I’m not sure why. I just didn’t. It seemed easier in the moment to be able to wiggle the fabric as I sewed to make sure it was butted up nicely to the piping (which you will follow again as a guide with the zipper foot). If I have COMPLETELY lost you now, just take a look at the photo below. It should clear things up for you. See how my pen line follows parallel to the seam between the top panel and edge (and the lines are 2″ apart)?

sewing window seat cushion

Once I finished sewing on the bottom panel, I was a little freaked out. My biggest fear was that this thing (that I just spent who know how long making) wouldn’t fit. There was no going back and I told myself that if it didn’t fit, our kitchen window seat would just have to live a life sans cushion. And I was ok with that. But guess what? It fit perfectly! All of my nitpicking paid off. Look at that beautiful zipper (and I’m saying beautiful as in the-very-best-I-could-do-for-my-first-time kind of beautiful).

diy window seat cushion with zipper

Time to Relax! 

It was nearly midnight, and I still needed to shower that night and get up by 6 am the next morning and hit snooze 3 times. I was totally spent. Don’t mind the giant box of fruit snacks next to the fridge, we like ourselves some fruit snacks.

DIY window seat cushion finished

Don’t let Travis fool you. He played zero part in all of this. Well… he helped build the seat, and he went with me to Joann fabrics to buy the trim fabric at the last second. More realistically, he plays the sit-on-the-dang-thing-and-enjoy-it role. Why can’t I ever play this role? Hopefully the dogs won’t realize this seat is comfortable because I will cringe if I come home from work and see them laying all over it.

window seat cushion

This is the face of one happy, accomplished girl. I conquered my first zipper, piping, and even bigger… my first seat cushion. Go me.

DIY bay window seat cushion

DIY window seat cushion

Loving this pattern! It has a slight silvery sheen to it.

window seat cushion

Look at that nearly straight piping. I’m amazed with how it turned out.

diy window seat cushion

diy window seat cushion

diy window seat cushion

If I can be totally honest, this project wasn’t too difficult. But it was a little challenging. I spent more time thinking than doing (the thinking part is key, so don’t skip it.) I told myself I wanted to add a zipper so I could easily make a new cushion cover with a different fabric making it easy to swap it out on occasion. HA! That won’t happen any time soon. I’ll have to wait until my goldfish brain forgets how much work this thing was…. so maybe an encore post of the new cover in another year? We’ll see…


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27 Responses to Sewing a Bay Window Seat Cushion

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  3. Chris says:

    For being an amateur in sewing skills, I am impressed! You did a wonderful job!

  4. DIANE MARTEL says:

    i love your window seat the cushion came out fabulous, i hope mine comes out your instructions will certainly help me, thanks

  5. geetika says:

    How does it stay put? Or does it slip down?

    • I thought about sewing some non-skid material on the bottom side of the cushion but I ended up not needing to. Since the seat is low, people don’t scoot off the edge which would knock it onto the floor. So in my case, it’s fine without snaps, velcro or non-skid to hold it in place. The only time is slides is when my little niece or nephew comes over. I’ll need to modify it when we have kids 😉

  6. Very cool!! Pinning this for when I decide to finally attempt some piping. I’m a VERY beginner sewer, so very nervous about all things sewing still!

    • Piping is very tricky to get positioned just right so I’d say just practice first and then dive into your actual project. I just dove in and ended up having to redo parts of it. Practice makes perfect! Learn from my mistakes 😉

  7. carole kozak says:

    exactly what I was looking for. Attempting my first window seat cover this winter. If mine turns out even close to the way yours is, I’ll be happy. 74 yrs. young and still learning. thanks for your candid instructions.

  8. Rebecca says:

    What a beautiful cushion! You should be very proud! I am trying to decide whether to try to make one myself or hire someone to do it. Thank you for the detailed instructions.

  9. AnnaMarie says:

    Beautiful! You’ve inspired this newbie seamstress!! 🙂 BUT I’m confused about choosing the foam…any tips/suggestions?

    • Thank you! For the foam, just make sure you get one continuous piece. You won’t be able to use scraps and piece them together, and trying to layer thin pieces on top of one another will be too tricky to squeeze it into the cushion cover because they’ll slide around. When you cut it, make sure to cut just a little at a time unless you’re positive you’ve measured correctly because trimming too much would be a costly mistake. I bought mine when it was on sale at Joann Fabric. I’m sure they’ll have a good Black Friday weekend sale coming up… might be worth the wait since it’s expensive. They have a lot to choose from but any 2″ foam will work just fine, unless you prefer something thicker. I don’t think I’d use anything thinner than 2″ though. It wouldn’t be very cushy. Hopefully all of this was helpful and good luck with your project! Please share photos afterwards. I’d love to see how it turns out.

      • AnnaMarie says:

        OMGosh thank you so much for the quick reply and for all of the super helpful information 🙂 You must realize that as a newbie seamstress, I have to act while motivation is high, hehe!! I do have 2″ thick foam but it’s this from J’s (regular density) – I’m hoping that it will still be ok? Or do you think I should go from a higher density foam? It’s just a small window cushion for my daughters’ tiny windows so they can sit and read occasionally behind their drapes ;), and I was going to add a quilt batting underneath the fabric too…

        Thanks again! New follower!! 🙂

      • If the foam passes a test run of just sitting on it, then it should work just fine. I laid a bunch out in the aisle at Joann’s and sat on them to figure out what thickness I wanted. I’m sure people were staring at me… oh well. Looking back, I wish I had added the batting to mine (I guess I still can). I think it would be a little softer.

      • AnnaMarie says:

        Thank you again – you rock!! 🙂 🙂 Hope to share photos soon!! 🙂 My pre-teen girls will be picking out fabric this week 😉

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  11. Ashley, I have just discovered your blog through Pinterest searching for a tutorial on how to sew a bay window seating cushion with piping for total beginners. Your post pops up and I am hooked! Your instructions are perfectly clear and easy to follow. I love your bay bench! I’ll be sure to report to you as soon as I have my cushion ready to show off. But there’s more! Your dining room is my dream dining room! I mean the colors – olive/sage combo with white chars and dark table top! I’ll be your frequent visitor here from now on 😉

    • Aww thanks so much! I feel bad because my blog has been totally neglected this Summer. Life has thrown me a few curveballs these past couple months but I hope to get back into the groove soon. I’d love to see photos of your cushion when it’s all done. I’m glad my blog is helping you out and thanks for reading!

    • Penelope says:

      Hello Ashley. I’m not exactly new at sewing but, have not made a boxed cushion before. I was searching for a tutorial when I discovered your site. I enjoyed your humor as well as the instructions. I was however, a little confused with your explanation regarding sewing the bottom fabric to the sides. The picture didn’t really help either. Could you explain a little further? Thank you.

  12. Elise says:

    I just followed your instructions to make my very own window seat cushion (my first piping, too) and it came out great! I couldn’t believe that the project went off without a hitch, and it has to be thanks to your awesome instructions!

  13. Dameon says:

    If you don’t mind me asking, what’s the shade and name of the green on the wall?

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