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How to Seam Seal a Tent or Tarp

Seam Sealing

Applying Seam Sealer with a paintbrush


Seam sealing is a procedure necessary for most tents and tarps to keep water from leaking through the stitching.  This is caused by the size of needle and thread the manufacture used while constructing the piece of outdoor gear.  Overlooking this process, may lead to a miserable and wet nights sleep in the backcountry.  Don’t let this project intimidate you, honestly it’s the easiest thing a hiker can do!

Helpful tips:

  • Seal the seam on the outside of shelter. That’s where the rain will fall and you need to seal the stitching there to repeal water.
  • Make sure its not too hot 6o Fahrenheit or 15 degrees Celsius is the ideal temperature to seal up your shelter, and a humidity that is not too high (below 80%).
  • Pitch the shelter tight (wrinkle-free) before you start to seal it.

Now lets get started sealing the seams!  Find a flat spot to pitch your tent or tarp, where you can leave it for at least a day or to cure overnight; until the sealer is dry.  Somewhere secure from rain and where there isn’t going to be wind is best as wind may blow dirt onto the sealer and foil your whole project.

What you will need:

  1. Paintbrush
  2.  Cup or something to mix up in
  3.  Cardboard stencil cut to the width of your seam (or just a steady hand)
  4.  Damp cloth
  5.  Mcnett Silnet for Silnylon, or if it is a PU coated material, Seam Grip
  6.  Paint thinner

Start by mixing 1 part Silnet sealant to 3 parts paint thinner in a cup.  Stir until it is about an olive oil consistency. This will make sure it’s easily applied and rubbed into the seams. The goal is to soak the mixture into the stitching, where the water could penetrate.

Brush in the thinned mix carefully and use the damp cloth to clean up any spills. I pre-cut a stencil card custom to the width of my seams and used that as a template to help reduce spills.  You can use a paintbrush or foam brush, just make sure to apply some pressure so that it works its way into the seams.  As the Silnet it is thinned by the mixture, it will soak into stitching nicely.  After the working area is complete, leave it to dry. I suggest focusing one seam at a time.  You should have a nice clean finish after it dries. Make sure you come back after an hour or so, so you can spot check any missed areas.

On high stress areas like the anchor points; add a few dabs of Silnet straight from the tube to reinforce those areas. Then allow 24 hours to dry. Pack away until your next backpacking adventure. Next time it rains overnight on your camping trip, sleep well; not worrying about water leaking into your shelter.


*Bonus Tips*

  • Baby powder or cornstarch can be sprinkled over the dried area if you’re worried about tackiness.
  • Apply a few strips of the seam sealer/ paint thinner mixture to the floor of your tent to prevent your mat from sliding during the night!


Gear tip written by Trail Ambassador Martin Rye and Editor – updated in August 2015 


6 Responses to How to Seam Seal a Tent or Tarp

  1. Doug July 18, 2014 at 11:42 am #

    White spirit – paint thinner. I use generic – Coleman white gas, which I use with my liquid-fuel stoves.

    • Editor July 21, 2014 at 5:12 am #

      I’ve tried white gas and had poor results with it – it turns the seam sealer a milky white. Paint thinner is the way to go because it provides a clear transparent seal.

  2. Len July 18, 2014 at 6:29 pm #

    I also use silicone thinned with mineral turpentine to do the same thing. Takes a bit of mixing initially, I find it works best when the mixture is very liquid and will wick into the sewn fabric join. Great idea using a masking card.

    I’m not sure about the use of petroleum based thinners as they could damage the integrity of the fabric and thread as they are mostly petroleum based also, but maybe it is irrelevant due to the stabilizers used.

  3. Martin Rye July 19, 2014 at 3:05 pm #

    Mineral spirits (paint thinner) is the way to go. The masking card and a wet cloth to mop up any runs that the card missed is ideal to ensure a neat finish. I could not comment on using white gas. As I have never used it.

  4. jwmilstein July 19, 2014 at 8:30 pm #

    Mineral turpentine and mineral spirits are two names for what should be the same thing.

  5. Colin Parkinson August 2, 2014 at 2:29 pm #

    Don’t forget to sprinkle some corn starch on the seam after they dry as it will stop the seams from sticking together. Even dry silicone seam sealer is tacky.

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