Do Ultralight Backpacking Tents Need to be Seam Sealed?

Most ultralight backpacking tents are made with one of the following coated fabrics: siliconized nylon, siliconized polyester, and dyneema composite fabrics, also called, silnylon, silpoly, and DCF respectively. Some ultralight tents are also made with nylon or polyester that’s coated on one side with silicone and the other with polyurethane (Sil/PU) or polyether urethane (Sil/PeU). The fabric coating that a tent is made with usually determines whether a tent can be factory seam-taped or whether it must be manually seam-sealed to prevent rain from leaking through the seams into the living space.

Waterproofing Tent Seams

When tents are sewn together with needle and thread, the needle creates many small holes where the thread passes through the tent fabric that can leak water when it rains. These must be manually seam-sealed with silicone tent sealant if they’re made with silnylon or silpoly. If you’re interested in what’s involved, see our article How to Seam-Seal a Tent that describes the materials, how to mix them, and how to seam seal a silnylon or silpoly tent.

Its' best to dilute silicone seam sealer with pain thinner so it soaks into the seams and waterproofs them
It’s best to dilute silicone seam sealer with paint thinner or white gas so it soaks into the seams more easily and waterproofs them.

Silnylon and Silpoly tents that must be seam-sealed before use

I’ve seam-sealed a lot of silnylon tents and tarps in my day and it’s a messy process that’s well worth paying someone else to do, even if it adds a small amount to the cost of a tent. Tarptent, Six Moon Designs, Lightheart Gear, and Yama Mountain Gear all offer seam-sealing on the silnylon and silpoly tents they sell for a small add-on fee.

Tent fabrics coated with polyurethane or polyether urethane are factory seam taped to make them waterproof, using tape that looks a lot like transparent scotch tape, only is much stickier and will usually last for the lifetime of your tent. The seams on tents made with Dyneema DCF are also seam-taped when they’re manufactured using a specially formulated Dyneema tape.

Sil/PU, Sil/PeU, and DCF Tents that DO NOT need to be seam-sealed

There are also some ultralight tents that have waterproof seams that are not factory seam-taped and don’t have to be manually seam-sealed. For example, the SlingFin Splitwing Tarp and the SlingFin Portal Flysheet are made using 2-sided siliconized nylon 66  and use double-needle lap felled seams. This means that the needle goes through four layers of fabric, such that the water pressure from rain really doesn’t get high enough to force water through the seam. However, this method of construction is fairly rare among ultralight backpacking tent manufacturers.

More Tent FAQs:

 

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