How to Create Waterproof Seams

When you’re making a boat cover, outdoor storage cover or tarp, you want to be sure that it will keep your possessions safe, clean and dry. But did you know that when you sew, the holes the needle creates in the fabric can leave your cover susceptible to leaks? If you’re concerned with leaking seams, never fear. We're going to share a few ways you can seal up your seams to keep them as watertight as possible.

Testing Anti-Wick Thread’s water resistance

If you’re sewing a new project, you can add built-in protection from leaks by using an antiwick thread. Antiwick Thread is a bonded Dabond polyester thread with a wax coating that was specifically designed to prevent weeping seams. The way it works is that the wax plugs the stitch holes to prevent water from leaking through. It’s the same Tex 90 polyester thread that most marine fabricators use, just with an extra coating so it’s still UV, mildew and abrasion resistant. You can see for yourself just how well Antiwick Thread works by watching our test video.

Use a Seam Sealer

For those who already have thread to use or would like to waterproof the seams on an existing cover, you can use a topical seam sealer. We recommend using Iosso® Seam Sealer on cotton, polyester, Sattler® and other synthetic woven fabrics. This seam sealer will effectively protect and seal your seams without changing the look and feel of your fabric. Iosso Seam Sealer comes with a sponge applicator for easy application directly to your sewn seams. You’ll get the best results if you apply the seam sealer to both sides of the seams. Seam Sealer should be reapplied periodically if your cover sees a lot of harsh weather and after each cleaning.

To protect seams on a vinyl tarp or cover, you can use HH-66 Vinyl Cement as a seam sealer. Just carefully brush the HH-66 right on top of the sewn seams on the underside of the fabric only. The glue will dry clear and after it has cured it won’t be sticky. Learn more about HH-66 as a seam sealer in this video.

You can find all of these great waterproofing products right here at Sailrite®.