How to waterproof a canvas tarp

Updated February 21, 2017

The right application of waterproofing can prevent mould and mildew from forming on a canvas tarp. Tarps act as protection for boats, lawnmowers or other items which are left out in the elements or stored in cool, damp places. The tarp, if treated properly, keeps dirt and water off the covered items. However, without the proper waterproofing treatment, rain and other moisture sources may begin to penetrate the canvas and allow mould and mildew to form on the tarp.

Spread the canvas tarp, top side up, in a clean, dry area.

Mix a small amount of dish detergent in a bucket of water.

Wash the top of the tarp using a clean cotton rag and the detergent mixture. Rinse with fresh water and allow to dry.

Spray fluoropolymer-based waterproofing horizontally across the tarp, working from the top downward. Allow the product to sit on the tarp for the amount of time recommended by the manufacturer.

Apply a second coat of the waterproofing vertically across the tarp, working from left to right. The checkerboard application assures that all points are covered. Allow the tarp to dry completely before using.


When prepping the tarp, concentrate on any spots of dirt or grease. Removing these spots is essential to even application of the waterproofing agent.


Waterproofing agents will not fix tears or rips in the tarp. Repair any tears or rips before treating the tarp.

Things You'll Need

  • Dish detergent
  • Bucket
  • Clean cotton cloth
  • Spray-on fluoropolymer-based waterproofing
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About the Author

Sidney Johns began her writing career in 1993 after moving to Florida. The former teacher and surgical technician worked in the home improvement industry prior to earning a Bachelor of Science in education from Indiana University. While on hiatus in 2004, Johns studied holistic healing and organic growth and gardening.