♥ TL;DR: For the majority of Sew Toot patterns, I use typically use a rigid closed-cell foam for carrier waistbands and plush (also called “luxury”) high-density open cell foam (1″ inch) for carrier shoulder straps.

________________________________________________________________________________________________

Foam is what makes a DIY baby carrier comfortable to wear for hours, but it’s also one of the most confusing supplies to source (and one I get asked about most!).

If you’ve ever stood in a craft store holding a roll of upholstery foam and wondered is this the right stuff? then this post is for you.

We’ll walk through the main types of foam, what each one is like to sew and it’s wearing qualities, and which parts of a carrier need which kind of foam.

What Foam Does in a Baby Carrier

When we’re using foam in a baby carrier, we’re using the foam to spread baby’s weight over a wider area, which provides cushion and spreads the weight over a larger area so the straps and waistband don’t dig in or create pressure points. The job of foam is to provide comfort and give the finished carrier shape.

Keep in mind, it’s not the foam that’s holding baby up. The webbing, fabric, and stitching do that, which is why every Sew Toot pattern spells out reinforcement stitching, overlap, and seam allowances so carefully.

Open-Cell vs. Closed-Cell Foam

Foam for baby carrier construction falls into one of two groups, and knowing which group a foam belongs to answers most questions about whether it belongs in a carrier.

• Open-cell foam has tiny air pockets that connect to each other, so air and water move through it. It’s soft, squishy, and breathable, (think chair cushion) but it soaks up water, takes a long time to dry, and can flatten over time through repeated compression. Upholstery foam and memory foam are both types of open-cell foam. My personal favorite for carriers is “luxury” “high-density” open-cell foam.

   

• Closed-cell foam has air pockets that are sealed off from each other. It’s firmer, springs back after it’s squeezed. It sheds water and it dries quickly. Keep in mind that closed cell foam can runs a bit warmer because air can’t pass through it. Hiking backpack straps and waist belts are usually made with closed-cell foam.

Foam Types Compared

Cross-linked polyethylene and EVA are the two foams that work best for carrier waistbands and shoulder straps. Here’s how the common options stack up.

• Cross-linked polyethylene (XLPE). Cross-linked means the foam is made with extra bonds between its molecules, which gives it small, even cells and a smooth surface. You’ll find it sold as XLPE or under brand names like Minicel and Volara. It’s light, durable, and sews cleanly.
• EVA. EVA stands for ethylene-vinyl acetate. It’s a closed-cell foam with a springy, slightly rubbery feel, and it resists tearing better than most foams. Craft foam sheets, some yoga mats, and interlocking floor tiles are often EVA, though quality varies a lot from product to product. These can be easier to source for in-person foam shopping.
• Camping pad foam. Roll-up sleeping pads are made from closed-cell polyethylene or EVA, which makes them a handy budget source. Keep in mind that cheaper pads can flatten quickly with use, or potentially try to roll away from the body if they aren’t rigid enough, so squeeze and fold a piece before you commit to it.
• Non-cross-linked polyethylene. This is packing foam, like the stiff sheets that come wrapped around electronics. It has larger, rougher cells and creases for good when it bends, so it breaks down quickly in a strap.
• Polyurethane upholstery foam. This is the soft foam sold for cushions and chair seats. You may also see it with a thin fabric backing, sold as sew foam or scrim foam, which upholsterers use for padded and pleated designs. It feels comfortable at first, but it soaks up water and flattens with use, and it isn’t made to provide support.
• Memory foam. Memory foam feels wonderful in your hand, which is why so many people ask about it. It softens with body heat and springs back slowly, so under the steady pull of a strap it flattens and stays flat.
   

What Foam Works Where in a Baby Carrier

Each part of a carrier asks something different of its foam, so the firmest foam goes in the waistband and the softest goes where it touches your baby.

• Waistband. The waistband needs the firmest foam in the carrier, because it has to keep its shape for your baby’s weight to sit on your hips.
• Shoulder straps. Strap foam exists to spread weight across your shoulders, while cushioning against the load. It needs to be flexible enough to mold to the wearer, too. This matters most for curved straps, like the ones on The Little Pick-Me-Up. I recommend a high-density 1″ open cell foam for should straps.
• Leg padding. Leg padding runs along the edge of the body panel where your baby’s legs come out. A thin, soft layer cushions the backs of their knees. Sew Toot patterns typically use stuffing for leg casings, but you could also sew in a thin piece of open cell-foam or sew or stuff in quilt batting scraps.
• Onbuhimo straps. An onbuhimo, like The Riser, has no waistband, so all of your baby’s weight sits on your shoulders. That makes good strap foam even more important. A good quality high-density foam will be very important for this style of carrier.
• Doll carriers. Dolls are light, so thin foam or quilt batting is plenty for The Mini and The Little Transporter. One perk is that you can probably use up some scraps!

What to Look For When You Buy Foam

When you’re shopping for carrier foam, start with the cell type, then check density, thickness, and how well the foam springs back.

• Cell type. Choose closed-cell foam for waistbands and open-cell for shoulder straps.
• Thickness. Use the thickness your pattern calls for. Going thicker makes straps stiffer and harder to sew, and it can change how the pieces fit together.
• Density. Density is how much a block of foam weighs for its size, usually listed in pounds per cubic foot. Keep in mind that a higher density generally means firmer foam, which is good when we’re looking to avoid compression.
• Recovery. Recovery is how well foam springs back after it’s squeezed. Foam with poor recovery “packs out,” which means it flattens for good and stops cushioning. Squeeze a sample hard and watch how quickly it bounces back.
• Heat. Closed-cell foam runs warmer than open-cell foam. If you live somewhere hot, a breathable outer fabric helps, but also consider breathable foam options like a thinner open-cell foam.

Sewing and Washing a Carrier with Foam

Getting foam into the straps is the step most makers dread, and the most important thing is to go gently.

• Inserting foam. Ease the foam into the strap a little at a time. Pulling on it can tear it, and one maker tore her strap foam right in half on her first try. My strap foam tutorial walks you through a trick that makes this much easier.
• Sewing through layers. A walking foot and a slightly longer stitch length help your machine feed evenly through fabric and foam. Go slowly at the thickest spots.
• Washing. Closed-cell foam handles the wash well and dries quickly, which matters when a carrier sees drool and spit-up. Open-cell foam holds water for a long time and can mildew if it doesn’t dry all the way through. I recommend spot cleaning when possible, and when soiled, hand washing. Always hang your carriers to dry.

Baby Carrier Foam FAQ

Can I use a yoga mat for baby carrier foam?

Some yoga mats are closed-cell EVA and can work. I’ve seen quite a few people use yoga mats successfully for carriers in the Sew Toot Patterns Facebook Group. If the yoga mat doesn’t have enough rigidity, the waistband might of your carrier could potentially fold or roll forward from the lack of structure when a baby is inside of the carrier.  For The Voyager pattern (by sea version), a yoga mat would make for great straps. 

Can I use upholstery foam from the craft store?

The soft foam sold for cushions is open-cell polyurethane, so it can work for a carrier. Keep in mind that most foams sold in craft stores will not be high-density foam. Thank the craft gods if you find HD foam in person!

Does the foam affect how safe my carrier is?

Foam affects comfort. The fabric, webbing, and stitching are what carry your baby’s weight, so follow your pattern’s reinforcement stitching and seam allowances exactly, whatever foam you choose.