All About Cushion Foam Part 3: Anatomy of an Outdoor Cushion

Did you ever wonder what gives a cushion its cushy shape? Or how to protect a cushion from moisture from the inside out? Today, in third and final installment of our Cushion Foam Series, we’re going to examine the anatomy of a cushion and see how to add fluff and protection to your cushion foam. If you missed the first two parts of the series, be sure to check out our roundups of 4 Important Foam Terms to Know and 5 Types of Outdoor Cushion Foam.

If you cut a cushion in half, you’d most likely find a series of layers under the fabric stacked like a parfait. At the very core is the foam. On top of the foam usually is a layer of batting, and then there might be a thin layer of silk film, or other protective wrap.


Shape and Support with Foam

Choose the foam for your cushion based on your desired application and look. For a rounded look, choose a foam that can be wrapped in batting like open cell or polyurethane foam. Compressed polyester or polyester fiberfill are already soft, so they can fly solo in the cushion fabric. Closed cell foam is also generally used without any batting or wrapping.

Soften and Plump with Batting

Add batting to the foam to create a cushion with a plump, puffy look. The batting goes right against the foam, and is usually glued in place using a spray adhesive. Wrap the batting around the foam so both the top and the bottom of the cushion are covered, plus one side. If you desire, you can also wrap the batting so it completely encases the foam, folding the corners like wrapping paper.

Here’s a video that demonstrates how to wrap and glue the batting in place for a large, outdoor cushion.


Shrink and Protect with Silk Film

Whether you wrap your polyurethane foam in batting or not, we recommend using a silk film layer inside your cushion. This soft, noiseless film layer will act as an extra moisture barrier. The real bonus to using silk film is that after wrapping your foam in it, you can vacuum out the air to shrink the foam to 70% its original size. This makes it much easier to stuff the foam into a fabric cover. This shrinking feature is especially handy for foam wrapped in batting.

To use the silk film, cover and tuck the film loosely around the foam. Insert the vacuum hose into an open end of the film directly onto the foam and turn on. The vacuum’s suction will compress the silk film over the foam and shrink the foam. Turn off the vacuum and the foam will expand to original size.


That concludes our foam series. With all your new foam knowledge you’ll be all set to tackle new cushion projects! Browse our selection of cushion foams, batting and silk film at

Do you have any foam questions we didn’t cover? Leave us a comment, we’re happy to help!

  1. SueC56 said:

    I am making a cushion for an outdoor window bench. How do I make a piece about 80 inches long? Can I glue two pieces of foam together? Do I just use two pieces of foam in one cover without gluing?

    • Nikki said:

      Hi Sue,

      You could use a large piece of foam and cut it down to the exact size with an electric kitchen knife. Or if you want to use two smaller pieces, we recommend gluing the pieces of foam together using a spray adhesive like 3M Super Trim Spray. Here’s a link:

      On that page you’ll also find a video with instructions on gluing pieces of foam together. Then you should be fine to wrap the foam in silk film and add your cover!

      Here’s a link to our foam selection for you to take a look!:!Foam-Pillows

      Hope that helps!

  2. SueC56 said:

    I probably should have told you that I need foam that is 2 inches thick by 22-23 inches wide and will be covered with Sunbrella fabric and probably the silk film.

  3. christine walker said:

    we are making outdoor couch and are wondering what foam and fabric we ahould make the cuahions out of it will not be coveres so is possible to get wet! thank you for your help.

  4. R Summerlin said:

    I live in Florida where it is humid. If I use silk film on outdoor cushions for a covered porch (which does get wet in hard rains) won’t this promote mildew growth from the inside?

    • Nikki said:

      It depends on the type of foam you use. Polyurethane foam tends to take a long time to dry out, which also makes it more prone to mildew. The idea of the silk film is that it will prevent water from getting to the foam at all so, ideally, it prevents mildew growth. However, if the water should break through the silk film and get into the foam, it could mildew from the inside. If you use a DryFast foam, you should not use silk film so the water can drain out of the foam as intended. Hope that helps answer your question!

  5. Judi said:

    I am wrapping a foam patio cushion with dimensions of 73x26x3. How do I find silk film this size. I’m assuming I would need 1 piece to wrap cushion (i.e.: I cannot piece together the silk film). Thank you

  6. Donna said:

    What foam do you recommend for indoor sofa cushions – medium or firm?

    • Nikki said:

      Hi Donna,
      For indoor sofas we recommend any foam marked “high density.” So the medium or firm is your preference on how firm you’d like the seat to be. Most sofas use a “medium” firmness cushion. Here’s all our options for high density foam: Hope that helps you!

  7. r6lcc07 said:

    Hi, would you add anything to the measurements for the cushion covers to allow for the batting, or assume it compresses to nothing?

    • Hello, you can assume the compression between the foam and batting is sufficient, so no need to add to your measurements!

      • r6lcc07 said:

        Brilliant thanks!

  8. Hello, I think your site might be having browser compatibility issues. When I look at your website in Safari, it looks fine but when opening in Internet Explorer, it has some overlapping. I just wanted to give you a quick heads up! Other then that, fantastic blog!

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