SectionHiker.com Backpacking Gear Reviews and FAQs 
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.
Silnylon and Silpoly tents that must be seam-sealed before use
| Make / Model | Material | Sealed Seams | Weight |
|---|---|---|---|
| Yama Mountain Gear Cirriform DW 1 - Silpoly | Silpoly | No | 27.5 oz |
| Tarptent Tarptent Double Rainbow | Silnylon | No | 42 oz |
| Six Moon Designs Skyscape Trekker | Silpoly | No | 28 oz |
| Tarptent Rainbow | Silnylon | No | 37 oz |
| Lightheart Gear Firefly - Silnylon | Silnylon | No | 29 oz |
| Yama Mountain Gear Cirriform DW 2 - Silpoly | Silpoly | No | 34.8 oz |
| Tarptent Stratospire 1 | Silnylon | No | 38 oz |
| Six Moon Designs Lunar Solo | Silpoly | No | 26 oz |
| Tarptent Moment DW | Silnylon | No | 36 oz |
| Lightheart Gear Solo - Silnylon | Silnylon | No | 27 oz |
| Six Moon Designs Lunar Duo Explorer | Silnylon and Silpoly | No | 45 oz |
| Tarptent Notch | Silnylon | No | 28 oz |
| Tarptent Stratospire 2 | Silnylon | No | 45 oz |
| Lightheart Gear SoLong 6 - Silnylon | Silnylon | No | 32 oz |
| Lightheart Gear SoLong 6 - Silpoly | Silpoly | No | 32 oz |
| Six Moon Designs Haven Bundle Backpacking Tarp | Silnylon | No | 34 oz |
| Six Moon Designs Deschutes Bundle Backpacking Tarp | Silnylon | No | 24 oz |
| Tarptent Protrail | Silnylon | No | 26 oz |
| Lightheart Gear Firefly - Silpoly | Silpoly | No | 29 oz |
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
| Make / Model | Material | Sealed Seams | Weight |
|---|---|---|---|
| Durston/Drop X-Mid-2 | Sil/PeU Polyester | Yes | 39 oz |
| Durston/Drop X-Mid-1 | Sil/PeU Polyester | Yes | 28 oz |
| Gossamer Gear The One | Sil/PU Robic Nylon | Yes | 19.9 oz |
| Gossamer Gear The Two | Sil/PU Robic Nylon | Yes | 27.9 oz |
| Zpacks Hexamid Solo | DCF | Yes | 10.4 oz |
| Tarptent Protrail Li | DCF | Yes | 17.7 oz |
| Zpacks Duplex Classic | DCF | Yes | 19 oz |
| Zpacks Triplex | DCF | Yes | 21.9 oz |
| Tarptent Stratospire Li | DCF | Yes | 29.1 oz |
| Tarptent Tarptent Double Rainbow Li | DCF | Yes | 28.6 oz |
| Zpacks Altaplex | DCF | Yes | 15.4 oz |
| Tarptent Notch Li | DCF | Yes | 21.5 oz |
| Tarptent Aeon Li | DCF | Yes | 15.8 oz |
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:
- Do You Need a Tent Footprint for Backpacking?
- What are the Strengths and Weaknesses of Trekking Pole Tents?
- How to Prevent Tent Condensation
- How to Pitch a Tent on a Wooden Platform
- How to Dry a Wet Backpacking Tent
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“Silnylon and Silpoly tents that must be seam-sealed before use” This category should be re-labeled to “Tents Not Worthy of Purchase. Ever.” Why some manufacturer’s don’t seal their seams on waterproof layers is beyond me.
I also think it’s a stupid and antiquated practice to make tents that require seam sealing. People want a “complete” product they can use immediately after purchase. Forget Durston/MassDrop and Gossamer Gear who now seam-tape, the competition is Big Agnes and Nemo, which is why people still buy their products at REI.
It’s true that silicone coated tent can’t be seam taped. While sil/pu coated tents can.
Is that stupid? Antiquated? I guess that depends upon perspective.
Silicone coated tents are sealed once and protected for the life of the tent. They can be stored wet for months with no mold or mildew. A pu coated tent would be thrown away.
Sil/Pu tents still have that PU layer. It’s subject to mold, mildew and over time, delamination. Overall the lifespan of your shelter is diminished.
If you like spending money needlessly. By all means save yourself and hour’s labor. After all, think of all the more important things you could invest your time in.
Better yet spend three times the money and buy a Dyneema shelter. We sell those too.
All very rational Ron (who by the way, is the founder of Six Moon Designs), but most people who buy tents don’t use them more than a couple of times each summer. Those that use them more know to dry them before putting them away and how to repair the seams if they *ever* come undone. Or in our disposable culture they simply buy a new tent because they’re tired of the old one.
I also think that the competition on the basis of weight, although irrational, is so fierce in the cottage segment that brands can’t list the weights of tents after seam dealing or they’ll lose business. This weight fascination is irrational because it ignores the other reasons why one tent might be better than another in different circumstances. Which is why so many people end up buying multiple tents over the years.
I think it’s worth clarifying that any good sil/PU tent is using the newer PEU formulation for PU (polyETHER urethane) where mold, mildew and delamination are not issues. Newer PU totally solves those.
Thus, Ron’s argument against sil/PU is actually an argument against sil/PU but only against using old fashioned PU (polyester urethane). A dual coated sil/PEU fabric is ideal because it’s similar in strength in pure silpoly but can be seam taped and is non-slip for no downside. The main reason it’s not more common (yet) is because dual coatings and seam taping add a lot of production cost.
Ron, Skyscape Scout customer here. Do I have to seam seal it? I thought the seams we’re sealed already.
Hermia,
I suggest you contact Six Moon Designs customer support and ask. I’m pretty sure you still need to seam seal it even though it’s coated with polyurethane (PU).
Wait a second! You mean six moons sells PU coated yents too? Hard to square that with Rons comments. And they don’t even seam tape them? Hah!
Ron, not sure why you think it’s takes an hour to seam seal a tent. As an apartment dweller, I have to go to friends house and seam seal my tents in his backyard because I can’t ventilate the paint thinner fumes and I don’t want to drip seam sealer on my floor and furniture. Then I have to let the tent dry overnight and go back the next day to retrieve it. Talk about a total waste of my time!
Hmmm, as though they offer to seam-seal the tent before shipping it to you for …..$30. How much is your time worth?
If a backpacker is NOT seam sealing a tent to save weight then they are in the “ridiculous category” and cannot be reasoned with. Likely the same group that cuts ogg hiking pole straps to save weight not realizing how to utilize the straps.
Tarptent gives you the option, seam seal yourself or pay them a bit extra to do it. I always did it myself. TT Dyneema (Lithium brand) tents come seam sealed – but for the eye-watering price they certainly should.
Seam sealing ain’t “rocket surgery” so do it and “quityerbitchin’ “.
Just a reminder that Big Sky International has been making both sides silicone fabric tents for more than 10 years that do not require the customer to seam seal the tent for using.
I would also like to mention that the same fabric, such as 30D nylon rip stop, that is double coated with silicone has a tear strength 2x stronger than the same fabric with one side silicone and one side PU coating so the fabric is not only lighter, but much stronger than the fabrics that most big box tent makers use.
Bob
Big Sky International
So does Hilleberg for that matter. How does Big Sky get it’s seam tape to stick to the silnylon or do you not use tape at all?
Seam tape cannot be used on fabric that has silicone coating on both sides because the seam tape will not stick to the silicone.
Bob
Big Sky International
so what do you do to seal the seams?
Phillip,
The majority of the seams on LightHeart Gear tents are as you describe in the end of the article – lap seams done on a double needle machine – especially the ridge line seams. Trust me, these still need to be seam sealed, a prolonged rain will quickly leak through these seams and wet the hiker inside
A few comments here:
1) As Judy from LHG mentions, DNLF seams aren’t that great. Whether a double-needle lap felled seam works well enough to keep water out without seam tape/sealing depends on the geometry of the shelter (e.g. the slope of the panels), and how waterproof you expect it to be. SlingFin seems to be having good results with this technique, but seemingly no one else is finding it sufficient. For example, MSR switched most of their 2018/2019 models to this technique instead of seam taping, but customers widely complained about leaking tents so MSR ended up recalling a large portion of their 2018-2019 tents to be seam sealed:
https://www.reddit.com/r/CampingGear/comments/e9nwoe/psa_msr_tent_recall_check_your_tents/
We prototyped the X-Mid 1P and 2P in this DNLF seam construction method because it was appealing to ditch the cost and weight of seam tape, but it just wasn’t waterproof enough for sustained rain, so we kept the factory seam taping. There are certain seams where it can work, but I don’t think it’s good enough to be a widely used technique. As Judy mentions, seams getting a lot of water on them will leak eventually. Risking that for the sake a few grams seems unwise.
2) Arguments for pure sil that cite tear strength advantages (e.g. Bob’s comment that sil only is 2x stronger than sil/PU) are usually unfair to sil/PU because (1) a good modern Sil/PU is probably Sil/PeU which doesn’t have the strength issues of traditional PU, and (2) you don’t have to evenly apply both sil and PU coatings. You can apply the same amount of sil as someone else using pure sil (to get that strength increase) and then ALSO add some PeU to the other side (which doesn’t hurt tear strength) to get a fabric that is just as strong as pure sil without the downsides of pure sil (can’t seam tape, very slippery floors). There’s no reason other than cost not to do this.
3) A quality sil/PeU coated fabric also doesn’t have the other weaknesses of traditional PU that have mentioned in some of these comments (e.g. mold, flaking, yellowing). Sil/PeU is a great way to go because a fabric with sil on the outside gives good tear strength while PeU (aka PU but not to be confused with traditional PU) on the inside allows for seam taping, and further eliminates the issue of sil floors being super slippery.
IMO, there’s no good reason to use pure sil other than that it’s cheaper (a quality sil/PeU is harder to produce because you’re applying two different coatings at carefully controlled depths of saturation). Companies use pure sil because it’s widely available, cheaper, used to be the best before PeU came along, and it lets them shift seam sealing to the user, so they benefit from lower costs and being able to claim lighter weight specs, even though both an illusion (since user seam sealing immediately adds weight and cost after purchase).
Factory seam taping is better because it’s far less hassle, lasts better (true for modern seam tapes), and it provides higher performance because user seam sealing is prone to problems (e.g. missing spots, or having thin spots, or not diluting the sil enough to soak in properly). With the X-Mid we pay more for Sil/PeU fabrics, so we can then pay more for seam taping, because that best serves the users interests. Factory seam taping saves hassle and cost, and is consistently higher performing than user seam sealing.
4) I encourage other manufacturers not to spread outdated information that unfairly represents modern PeU/PU. Traditional PU (polyESTER urethane) was pretty terrible stuff with big losses in strength and durability issues (e.g. peeling/yellowing) but nearly everyone has moved on from that to modern PU (polyETHER urethane aka PE or PeU) which is vastly better. It doesn’t degrade when stored wet, and doesn’t cause large losses in tear strength (PeU commonly increases tear strength like sil). Sil/PeU fabrics are the best woven fabric for modern lightweight tents, and the sooner everyone moves to that instead of spreading misinformation about it, the more customers will benefit.
– Dan
DurstonGear.com
Is modern PE better than the PE from 2017? I bought a trekking pole tent that year (not a Durston) which began to peel its seam tape just 5 years later. Now, 6 years after purchase, the peeling is extensive. I had always let it dry out indoors for 24h before being put away in my gear closet (not a basement, attic, or garage). Perhaps PE tents need to be stored loosely as well? Mine went back in the sack it came in. Regardless, it seems like an underwhelming lifespan, and not significantly better than PU tents that I stored in the same manner.
If you bought it in 2017, it’s probably not PE, but PU. I can’t recall any tent using that fabric/coating that far back. It’s a relatively new thing, only a few years old. Hard tp generalize though from your experience without knowing what it is you bought.
I think it’s PE because it was in the specs (Tensegrity 1 FL), as published by SD (and copied down by me) at the time:
Fly Fabric: 20D Polyester Ripstop, Silicone/1200mm PE, FR
Floor Fabric: 30D Nylon Ripstop, WR/3000mm PE, FR
These specs can be confirmed at the Internet Archive:
https://web.archive.org/web/20171109074819/https://sierradesigns.com/tensegrity-1-fl/
Also, Michael Glavin talked about it being part of the re-design of the tent in a BPL thread.
https://backpackinglight.com/forums/topic/93583/#comments
“If a tent wears out, it is usually do to PU degradation. We are mitigating this with our PE coatings on our FL versions (though don’t be confused, PE is still Polyurethane, not Polyethylene) These improve matters somewhat, but still I HATE these coatings.”
He then goes on to talk favorably about silicone coating, which was put in the Tensegrity’s Elite line.
Gotcha. I has another thought this about on my walk today. You said the tape was peeling off, not that the tent fly/fabric was getting sticky which is what usually happens to PU. Maybe you should just replace the tape or get SD to do it on a warranty if there is one.
Looking at the small print of my tent instructions and warranty, the tent is indeed to be stored loosely, when stored for “extended periods.” So that’s on me; I knew it true for bags and quilts, and that tents must be stored fully dry. But requiring loose, out of bag storage … I missed that. Probably good advice generally.
Funny, I have some other PU-coated gear of the same vintage (+/- a couple years) that is doing fine in their storage bags. But one difference I see is that their stuff sacks are generously cut. Not oversized, just big enough that it’s not a wrestling match to get the items back in. Perhaps that helps significantly. Regardless, I guess I need to allocate more hanging closet space in the future.
Thanks for the feedback, Philip – it led me to find this info.