Seam Sealing a Tent or Tarp

Seam Sealing is the process of treating the stitch holes and seams in gear made from waterproof fabric to prevent them from leaking when it rains or snows to achieve maximum waterproofness. Tents and tarps of all types and ages often require some degree of seam sealing to prevent moisture from dripping through and onto your sleeping bag. While many new tents come with factory taped floors and fly seams, there are some manufacturers who still require that you seal your tent or tarp by hand.

There are a number of commercial products for sealing tents available at most outdoor retailers. I prefer McNett's Outdoors SilNet, a silicone based product. Silnet can be applied with a brush but I prefer to use a plastic syringe, when possible,  because it gives you better control and requires less sealant.

 Silnet Silicone Seam Sealer

I recently seam sealed my new Black Diamond FirstLight tent in preparation for early spring. Before I began, I waited until the temperature outside was well above freezing and I set the tent up in my garage with the door open for ventilation purposes. Next,  I made sure that all of the seams were clean and free of debris and carefully identified all of the seams that I wanted to seal.

I began by sealing all of the seams where two panels of fabric met using my plastic syringe.  I laid down a thin bead of sealant just above the seam and let gravity pull the sealant into it. You can see this in the photo below. The syringe gives you a lot more fine motor-control than a brush and helps accelerate the process. if you've laid the sealant on too thick, you can run your finger or a sponge along the seam to prevent droplets from forming.

Seam Sealing a Tent

Next, I used the brush to cover seams where the stitching is visible on the outside of the tent, around the awnings and the reinforced corners. For visible stitches, I squeezed the sealant onto the brush and painted it directly on.

After covering all the seams and stitches, I left the tent set up in my garage for a few days to let the sealant dry. After that, I did a final inspection of all the seams and used the brush to paint on touch ups. When I performed this final inspection, I tied the top of the tent to a rope and hoisted it up to hip level so I could look at all of the seams more easily. When I was finished, I lowered the tent and left it in the garage for a few more days to dry.

The process of sealing a tarp is similar. First you need to stretch out the tarp in a windless, but well ventilated area. Next decide which seams you need to seal paying particular attention to the ones that may leak water onto you when they get wet. This will vary depending on the shape of the tarp. Then apply the sealant using a syringe or brush depending on the type of seam and let it dry for a few days.

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11 Responses to Seam Sealing a Tent or Tarp

  1. TentSweat May 17, 2008 at 1:11 pm #

    Where can you buy one of those syringes at?

  2. earlylite May 17, 2008 at 6:18 pm #

    I got mine on Amazon, I think. Just search for "plastic syringe". They work great for seam sealing a tent.

    • ohzie May 1, 2014 at 3:22 pm #

      also remarkably useful for jello shots.

  3. BW August 16, 2009 at 12:55 pm #

    Interesting technique, I am going to give it a try right now. The tent is 1/2 done, but I haven't had as much control over the sealant as I want.

    I have one of those syringes upstairs – it was for irrigating the sockets where my wisdom teeth used to be! If you have a good relationship with an orthodontist s/he might be able to hook you up.

  4. dchyde March 27, 2010 at 6:13 am #

    Do you need to seal the bottom of the tent or are the Black Diamond tents already sealed on the bottom? Thanks.

  5. Earlylite March 27, 2010 at 9:43 am #

    I sealed my firstlight tent where the bathtub floor meets the walls. But Black Diamonds EPIC tents wouldn't be my first choice for camping in rainy conditions. They really shine for winter camping when you want a lightweight single walled breathable tent in consistently freezing temperatures. That's mainly when I use mine.

  6. Chris October 6, 2010 at 11:36 am #

    Do you use straight Silnet when sealing your tents or do you opt to "dilute" it with mineral spirits before using the syringe for application?

  7. Earlylite October 7, 2010 at 12:44 pm #

    These days, I cut it with about 40-50% paint thinner and apply it with a small paint brush or the brush that comes with silnet. Works just as well, but is lighter weight and you need less silnet to seal a tent/shelter.

  8. Dawn March 4, 2012 at 4:20 pm #

    We just bought a Northwest Territory Blue Ridge Bay 12 person tent. it is 15×15. I like the sound and method you describe. Approx. how much sealer would you suggest I purchase? I hate getting in the middle of something and running out and having to go back to the store :) Thank you! This is the first site that I came across that I can actually ask a question like this!

    • Earlylite March 4, 2012 at 4:55 pm #

      Your tent’s fly is seam taped, so you really shouldn’t have to seam seal it.

  9. Dawn March 4, 2012 at 6:08 pm #

    Thank you Earlylite…I was reading the paperwork that did come with this tent and it said additional waterproofing was not necessary but additional seam sealer would be fine.

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