How to Sew a Knee-Rise Cushion With Fabric Backing

Item # X-HT-300464

Many seats in powerboats and sailboats have a knee-rise cushion built into the seating. This type of seating helps hold the occupant into the seat when underway and it raises their legs slightly for a more comfortable seat. Typically, these cushions are used in luxury boats. In our video tutorial, we’ll show you how to sew your own.

Learn how to sew a knee rise boat cushion.

There are a few things to consider before you begin this DIY project. First, if your existing knee-rise cushion has a backer board, then it is usually an outdoor cushion on a powerboat. If it’s in a cabin, then a backer board is seldom needed as it can damage the fiberglass that it rests on. A backer board can also make your knee-rise cushion bulky, heavy and hard to move around. This is actually very common for liveaboard boats because tables are lowered and made into full beds at night, so the cushions have to be moved all over.

If you want a knee-rise cushion but you don’t have boat seats with a backer board, then this is the video tutorial for you. The cushion that we'll be showing you how to create has a fabric bottom and a fabric pull with a zipper in it to separate the two heights of foam — the high rise foam and the low rise foam. This knee riser is perfectly straight, but there are some with a curve, and if we get enough demand for that type of cushion we may make a separate video tutorial for that.

We're going to be making this cushion out of Sunbrella Horizon, a high-performance engineered synthetic leather. Backed a five-year limited product warranty (the best in the industry), this fabric has what it takes to stand up to the rigors of your boat. It is completely waterproof and boasts a fanstic resistance to abrasion, stains, fading, mold, mildew and bacterial pinking. And with our incredible selection of colors and textures, you're sure to find a Sunbrella Horizon fabric that works for you. You can also use woven fabric for this project and the directions are the same.

You can use this type of cushion for your interior or exterior marine seating. Sunbrella Horizon, along with many of our other performance vinyl fabrics, can be used indoors and out. But just to be safe, you’ll want to make sure to pay attention to the recommended uses section when choosing a fabric for this project.

How did your cushion turn out? We'd love to see your finished photos in the comments section below and hear your thoughts on this video tutorial. Thanks for watching!

Video Chapters:

  • Selecting Foam - 1:17 min
  • Cutting Foam to Size - 2:37 min
  • Determining Plate & Boxing Sizes -5:54 min
  • Patterning & Cutting Fabric - 10:50 min
  • Installing Zipper on Fabric Pull - 16:30 min
  • Finishing Back Plate (Fabric Pull & Zipper Opening) - 18:46 min
  • Sewing High/Low Plates & Fabric Pull Together - 29:42 min
  • Preparing Boxing - 32:29 min
  • Sewing Boxing to Top Plates - 35:58 min
  • Adding a Top Stitch - 48:09 min
  • Sewing on Bottom Plate - 55:43 min
  • Inserting Foam - 1:03:37 min
  • Materials List - 1:15:33 min

Materials List:

  • High Density Polyurethane Antimicrobial Foam (Firm) - (#284F2480) & (#281F2480)
  • Foam Lock Spray Adhesive 12 oz - (#120464)
  • Fabric from Sailrite® – we used Sunbrella® Horizon Capriccio - (#10200-0016)
  • Cushion Underlining Fabric from Sailrite - we used Phifertex® Standard Vinyl Mesh - (#410123)
  • YKK® Continuous Zipper #5 White (Vislon® Chain) - (#28218)
  • Seamstick 1/4" Basting Tape for Canvas & Upholstery (36Yds) - (#122065)
  • Thread from Sailrite – we used Polyester V-92
  • YKK® Zipper Slider #5 Single Non‑Locking Pull (Vislon Chain) - (#103178)

Tools List:

  • Clear Acrylic Ruler 6" x 24" - (#102400)
  • Sailrite® Blade Foam Saw V2 with Carrying Case (110V) - (#121244)
  • Scribe‑All® Black Marking Pencil for Vinyl - (#121977)
  • Gingher® Scissors Right Hand Lightweight 8" - (#101017)
  • Sailrite® Ultrafeed® LSZ‑1 BASIC Walking Foot Sewing Machine - (#300601)
  • Ultrafeed® Industrial Sewing Table & Workhorse™ Servo Motor - (#120931)
  • Thread Clipper Kuroha - (#121908)
  • Seam Ripper Deluxe - (#18104)
  • Deluxe 5 1/2" Magnetic Sewing Guide - (#10359)