Foam Series: Anatomy of a Cushion

What’s Inside a Cushion? A Guide to Cushion Wraps, Fillers & Moisture Barriers

Ever wondered what goes inside a cushion cover? It’s not just foam — there are other materials that add softness, shape and protection. In this installment of our Foam Series, we’re diving into the layers that make up a high-quality cushion, from fluffy fillers to smart moisture barriers.

Cushion Layers: What’s Beneath the Fabric?

If you sliced a cushion in half, you’d see something like a parfait of materials layered on top of the foam core. These layers can include batting, polyester fiberfill, and protective wraps like silk film or spun-bonded fabric. Whether or not you need these extras depends on your foam type and cushion application — indoor, outdoor or marine use.

Let’s break down the most common cushion fill materials and wraps.

Batting: Adds Softness & Shape

Batting is the most common cushion wrap. It gives cushions their signature rounded, plump appearance and softens the edges for a more finished look.

• Installation tip: Batting is typically glued directly to the foam using spray adhesive. You can wrap it around the top, bottom and one side — or fully enclose the foam like a wrapped gift.
• Best for: Home and marine interior cushions.
• Not needed for: Compressed polyester or closed cell foam. These materials are already soft or buoyant, and adding batting may interfere with performance (like flotation).

Shop Polyester Batting

Polyester Fiberfill: For Extra Volume & Aesthetic Touches

Polyester fiberfill is a lightweight, fluffy filler used to plump up cushion corners and fill small gaps inside a cover.

• Usage: Optional and aesthetic — it’s not structural but can improve the cushion’s finished look.
• Pro tip: You’ll see us use fiberfill in our DIY cushion videos to create smooth, full corners.

Shop Polyester Fiberfill

Silk Film: A Moisture Barrier & Foam Shrinker

Silk film is a thin, noiseless plastic wrap that provides moisture resistance inside cushions.

• How it works: Wrap it over the batting layer before inserting the foam into your cushion cover.
• Ideal for: Outdoor seating and marine interiors where water exposure is likely.
• Do not use with: Closed cell foam or Dry Fast foam. Both are already moisture resistant, and silk film can block Dry Fast foam’s drainage capabilities.

Bonus Use: Shrink Foam for Easier Cushion Stuffing

Another major benefit of silk film? It can help you compress foam up to 70% of its size using a vacuum. This makes stuffing cushions much easier. Learn how in our post: “Using Silk Film to Shrink Foam.”

Shop Cushion Wrap Silk Film

Spun Bonded Pillow Protector: Breathable & Water-Repellent

Originally designed for DIY pillow forms, spun-bonded pillow protector fabric also makes an excellent cushion wrap.

• Benefits: Breathable, water-repellent and protective — great for outdoor and marine cushions.
• How to use: Sew a fabric “pillowcase” with one open end. Slide the foam (wrapped in batting) inside, then sew it shut.
• Similar to silk film: Offers moisture protection, but still breathable.
• Not needed for: Closed cell foam or Dry Fast foam.

Shop Spun Bonded Pillow Protector

When it comes to what’s inside your cushion, the choice is really up to you, but hopefully these guidelines will help you decide what will work best for you!

To learn more about foam be sure to read the other posts in our Foam Series.