How to Make a Foam Bolster for a Pontoon Boat

Item # X-HT-300447

If you are reupholstering boat seats and you notice the original foam is old, broken down and has lost its support, you need to replace it. This video will show you how to measure, cut and shape foam specifically for the rounded section of boat seats. Let's get started on this quick and easy foam shaping DIY. Our video will show you how it's done.

A look at our finished pontoon seat. In this blog, we're learning how to shape foam for the bolstered backrest cushion.

Often seen on pontoons and powerboats, there is a rounded section of foam at the front edge of the seat or along the top edge of the backrest cushion. This rounded section of the seat is called a bolster or knee-rise. Its function is to provide added lumbar support for the occupant by slightly lifting their legs. Even though this upholstered bolster section of the seat is rounded, we're going to show you how to cut and shape square pieces of foam to create a finished foam piece that is nicely and evenly rounded.

This is a two-part process involving cutting and shaping the corners of the square foam piece. Then we glue a layer of 1-inch foam on top of the first foam piece to achieve a rounded look. We recommend different types of foam depending on whether your rounded foam is for the seat bottom or backrest. If it's for the seat knee-riser, we recommend a High Density Foam with a medium or firm firmness for the main block of foam and the 1-inch top layer. The backrest cushion will experience less weight and pressure, so you can use a High Density foam with medium firmness for the block and soft firmness for the 1-inch layer. At Sailrite®, we carry a wide selection of foam types for all your marine, home, auto and outdoor upholstery and cushion needs.

Watch the video below to see how easy it is to cut, shape and layer square foam to create rounded corners.

Materials & Tools List:

  • High Density Polyurethane Foam (Medium) 4" x 24" x 80" (#284M2480)
  • Sailrite® Blade Foam Saw V2 with Carrying Case (#121244)
  • Tape Measure 120 Inch (#102986)
  • Medium Density Polyurethane Antimicrobial Foam (Soft) 1" x 48" x 80" (#181S4880)
  • Foam Lock Spray Adhesive 12 oz (#120464)