If you’ve ever wanted to update your sofa cushions, or change your outdoor patio decor without buying all new furniture, chances are knowing how to sew a box cushion (with piping and a zipper) would be a good skill to have.
It’s a great way to completely update the look of your room (or deck) without spending a ton of money.
And, since you’re picking your own fabric, there’s a great selection of different colors and patterns to choose from. So you can get exactly the look you want.
Fortunately, you don’t need fancy sewing skills to be able to make box cushion covers yourself. Although there are a couple of extra sewing machine feet you will probably want to get (see the supplies below)…they will make your life so much easier!
But before we get to the details of how to sew a box cushion, some of you may be asking…
What Is A Box Cushion?
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Box cushions or raised cushions are usually intended to be used as chair seats.
They consist of two pieces of fabric (a top and a bottom), often both have a piping surround, and a joining strip or gusset in the middle.
A typical example is a couch seat cushion, like the flamingo-patterned cushion on this outdoor sofa.
But often easy chairs, side chairs, benches, swings, etc. will also have a box cushion for added comfort.
The inside is usually foam wrapped with a layer of polyfill.
Okay…now on to our box cushion tutorial…
Supplies For Sewing A Box Cushion
- Coordinating thread
- Zipper by the yard with zipper pulls*. These are easier to use than pre-cut zippers because you can make them the exact length that you need them to be.
- Piping (or Welting) (optional)
- Paper (optional)
Step 1 | Make A Pattern For The Top and Bottom
Option 1 – Replacing Existing Cushion Covers
If you have cushions that already have covers on them, the easiest thing to do is use the existing cushion cover as a pattern for your new cushion covers.
1. To reclaim the pattern, carefully take the old box cushion cover apart using a seam ripper.
2. Then press the top piece of the old cover flat with an iron. This will be your pattern for the top and bottom of your new cushion cover.
Option 2 – New Cushion Covers
For new cushions, you need to know how wide and deep to cut the top and bottom fabric pieces.
1. To do this, measure how long and wide the cushion is that you are covering. Then add 1 inch to each of those measurements for the final cutting length and width.
2. Tape multiple sheets of paper together so you end up with one large piece of paper that is big enough to cover the top of your cushion.
3. Then make a pattern by drawing your cushion measurements out on the paper. Double-check that the size looks right by holding it up to your cushion. (It should be an inch longer and wider than the foam for your cushion).
Step 2 | Cut The Top and Bottom Fabric Pieces
1. Fold your fabric in half so the right sides are facing out. If your fabric has a pattern, make sure that the pattern is going in the same direction on both sides. If your fabric has stripes, make sure that the stripes line up on both sides of the fabric.
2. Lay your pattern on the doubled fabric. If your fabric has a pattern, like the flamingo fabric I used, be sure it is going in the right direction. i.e. the pattern will be facing up from the front of the cushion when it is sewn.
3. Pin the pattern to your fabric through all thicknesses, and cut out.
4. Mark the center of the back and front of the cushion for both fabric pieces by folding them in half and sticking pins in at the fold.
Step 3 | Measure For The Gusset
The joining strip (or gusset) will be cut in 2 pieces of fabric. So you need to take two length measurements and two width measurements:
Measurement 1. Long gusset length – Start at one of the back corners of the cushion. Measure all the way around the cushion to the other back corner (this should include both sides and the front of the cushion). Subtract 3 inches from this measurement for the final cutting length. eg. for 20″ square cushions, this would be 20″ + 20″ + 20″ – 3″ = 57″
Measurement 2. Short gusset length – Measure the length of the back of the cushion (the part that wasn’t included in the first measurement). Add 5 inches to this measurement for the final cutting length. eg. for 20″ square cushions this would be 20″ + 5″ = 25″.
Measurement 3. Long gusset width – Measure the depth of the cushion foam. Add 1 inch to this measurement. eg. for a cushion 3″ thick, this would be 3″ + 1″ = 4″.
Measurement 4. Short gusset width – The short gusset width will be 1 inch wider than the long gusset width (this is where the zipper will go). In other words, it should be the depth of the cushion foam plus 2 inches. eg. for a cushion 3″ thick, this would be 3″ + 2 1/2″ = 5 1/2″.
Step 4 | Cut The Gusset
1. Making sure that the pattern will be upright, draw the measurements for the longer gusset piece on your fabric with a pencil. It should be the long gusset length from measurement 1. above and the gusset width from measurement 3. above.
Note: If you have stripes in your fabric, make sure that they will line up with the stripes on the front of your top and bottom fabric pieces. Do this by matching the center mark you made on your top fabric piece to the center of the gusset.
2. Draw the shorter gusset piece on your fabric with a pencil using measurement 2. from above as the length and measurement 4. from above as the width. Again, make sure that the pattern will be upright and the stripes (if your fabric has them) will line up with the center mark of your top fabric piece.
3. Cut both gusset fabric pieces along your lines.
4. Then cut the shorter gusset in half length wise. You should end up with 2 shorter gusset pieces of fabric that are the same length as measurement 2. above but half the width of measurement 4.
Step 5 | Add The Zipper and Sew The Gusset Together
1. Sew the zipper into the two shorter gusset pieces that you just cut in half. If you’re not sure how to put in a zipper, you can find our step by step instructions HERE.
2. Find the center point of the front and back gusset pieces by folding them in half.
3. Then mark where the fold is with pins.
4. With right sides of the fabric together, match up the end of the long gusset piece with the end of the short gusset piece.
5. Sew the ends together with a 1/2 inch seam.
6. Repeat to join the other ends together so that you have a circle that will fit the entire circumference of the cushion with an inserted zipper that will extend 2″ beyond the back corners onto the sides.
Step 6 | Attach The Piping (Optional)
You can make box cushions with or without piping, but piping does help to define the edges. If you choose to go without, you can skip this step.
1. Pin the piping to the right side of the top and bottom fabric pieces so that the raw edge of the fabric is even with the raw edge of the piping.
2. Use the basting stitch on your machine (usually the longest stitch available) to sew the piping in place.
3. To make the piping fit around the corners more easily, clip notches in the raw edge.
Then it should wrap around the corner without pulling.
Step 7 | Sew The Top Of The Cushion To The Gusset
Before sewing the cushion closed, make sure to open the zipper part way so that it will be easier to open all the way later.
1. Match the marked centers (where you put the pins) of the gusset to those on the top piece of fabric. Make sure that the zippered edge of the gusset is at the back edge of the fabric. (If your fabric has a pattern it will be at the top of the pattern).
2. Carefully pin the top piece of fabric to the up side of the gusset making sure right sides are together and edges meet.
3. Clip notches in the gusset fabric at the corners to alleviate puckering (similar to the piping). Standing the gusset fabric up will also get it to fold around the corners.
4. Using a standard sewing stitch and a piping foot, sew the top piece of fabric to the gusset through all thicknesses with a 1/2 inch seam. It should be right at the edge of the piping.
If you have trouble with the corners, try making your stitch length shorter…it helps to make navigating the corners easier.
5. Repeat the same steps to attach the bottom piece of fabric to the gusset.
Make sure that the corners are aligned. If your material has a pattern, also make sure that the pattern is going in the same direction on both sides.
6. Sew all around the unfinished seam edges using a zigzag stitch. This will prevent fraying.
7. Turn the pillow cover right site out and insert the foam cushion.
Zip closed and you’re done!
A brand new cover for your box seat cushion!
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