How Waterproof is Silnylon?

How Waterproof is Silnylon?

Siliconized nylon, more commonly called silnylon, is a waterproof fabric used to make tents by many smaller manufacturers including Six Moon Designs, Tarptent, Mountain Laurel Designs, and Hilleberg which specialize in making ultralight backpacking gear or expedition-grade tents. It’s also sold in bulk for DIY-ers by Ripstop-by-the Roll, for people who want to make their own tents and tarp shelters.  Some companies like Lightheart Gear and Anti-Gravity Gear also use silnylon to make rain jackets.

Silnylon is available in different thicknesses, weights, and levels of waterproofing so it’s important to understand how the “waterproofness” of fabrics, is measured when comparing tents or rain jackets. Some silnylons are also coated with polyurethane, abbreviated as “PU” as in “Sil/PU”, and are best thought of as a separate fabric type, since it changes the properties of the fabric in a fundamental way. When people talk about silnylon, they really just mean siliconized nylon.

Waterproofing is measured using the hydrostatic head test, which measures the amount of water pressure a fabric can withstand before water starts to bleed through it. A column filled with water is placed over the fabric. As more water is added to the column, the pressure on the fabric is increased. When droplets of water begin to soak through the fabric, the height of the column is measured in millimeters and becomes the waterproof rating of the fabric.

For example, both the Six Moon Designs Lunar Solo Tent and the Tarptent Moment DW have a 3,000 mm waterproof rating (ie. hydrostatic head) on their rain flies and floors. The same waterproof rating test is also used for other fabrics including Dyneema DCF and Silicone Polyurethane (Sil/PU) treated Nylon, which is also used to make tents and rain jackets, making it possible to compare the waterproofness of tents or jackets made with different materials. Keep in mind that there are also many grades of Dyneema DCF and Sil/PU Nylon, so it really depends on what grade of material and waterproof coating formulation was used for a particular tent or jacket when making comparisons.

Waterproofness Comparison of Different Tents based on Hydrostatic Head

Many companies use a separate waterproof treatment on the rain fly and floor of their tents, since the floor is often subject to higher pressure (someone sitting on it in a puddle) than the fly and because ground abrasion wears down the floor’s waterproofing with use.

Make / ModelRain FlyFloorFabric / Material
Big Agnes Copper Spur HV UL 21,200 mm1,200 mmSil/PU Nylon
Big Agnes Tiger Wall UL 21,200 mm1,200 mmSil/PU Nylon
NEMO Hornet 21,200 mm1,200 mmSil/PU Nylon
MSR Hubba Hubba NX21,200 mm3,000 mmSil/PU Nylon
Gossamer Gear The One1,200 mm1,200 mmSil/PU Nylon
Durston/Drop X-Mid 12,000 mm2,000 mmSil/PU Polyester
Tarptent Moment DW3,000 mm3,000 mmSilnylon
Six Moon Designs Lunar Solo3,000 mm3,000 mmSilnylon
Hilleberg Niak5,000 mm12,000 mmSilnylon (Fly) PU Nylon (Floor)
Tarptent Aeon Li 8,000 mm8,000 mmDyneema DCF
Hilleberg Nammatj 25,500 mm20,000 mmSilnylon (Fly) PU Nylon (Floor)
Zpacks Duplex15,000 mm20,000 mmDyneema DCF

While the waterproof rating of Silnylon is a useful piece of information, silnylon tents and rain jackets can also leak at the seams, unless they’re seam-sealing with silicone. When silnylon is sewn, the needle and thread create many needle holes in the fabric that can leak in the rain. Unlike Sil/PU coated nylon or Dyneema DCF, these needle holes can’t be taped closed because the surface of silnylon is too slippery and tape can’t adhere to it. Most of the manufacturers who sell silnylon tents offer a seam-sealing service to you when you buy a tent from them, although it costs extra and will increase the weight of your tent by an ounce or two.

Companies that make rain jackets with silnylon use what’s called a bound seam to join together panels of fabric. This type of seam is very water-resistant but not waterproof. If you need it to be waterproof, for instance, if you have to hike in cold and wet conditions where hypothermia is a risk, you’ll want to seam-seal it yourself. This can be a messy process with a rain jacket and it’s often worth buying a seam-taped rain jacket instead.

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24 comments

  1. Very interesting and very cool. Thanks for the info, Phil!

  2. Awesome information, it’s a great capsule education in silnylon. Thanks!

  3. Great post. It gets into the weeds just enough.

  4. Maybe there is “perceived” waterproofness? For me silnylon “mists” in heavy rain and “wets out” after a few rainy days and nights. The Smokies are a high altitude rain forest and I’ve ditched all of my silnylon gear. Now, with dyneema tarp, poncho and underwear (no, not really) I actually enjoy back packing in the (summer) rain.

    • What a lot of people perceive as misting is just internal condensation (especially in a high humidity environment). Internal condensation tends to dry faster on Dyneema tents because they’re transparent and let heat through more readily which dries the internal condensation. But then again I know plenty of people with Dyneema Tents that swear by their towels. Of course, try sitting in a Dyneema tent on a sunny day and you’ll pass out from the heat.

    • I have used a Six Moons Luna Duo tent on multiple Alaskan backcountry treks lasting up to 12 days and have perceived misting in heavy rain by my sleeping bag get damp, but never actually wet.
      Also the floor wets through on wet tundra overnight, and wall wets through after a few days of constant rain. Condensation or icing, depending on temperature, is an issue, and it pays to have as much ventilation as possible, to set up for a sunny morning and to dry the inner and outer with a spare camp towel as soon as possible, and before packing away for the day.
      I love my Six Moons Luna Duo, and carefully pitched has stood up in high winds, where other tents have broken poles. My tent has been in use, since 2008, and every year since, ncluding a cross USA cycle trip in 2015.
      It gets some TLC every year with wall and seam reproofing with a silicon spray and seam sealer. A zip finally failed in high temperatures in the Australian outback in 2017, and was temporary sewn closed “in the field” and fixed when I got home. It also stood up to torrential rain in New Zealand fiordland on the same trip.
      I think it’s about done now, and there maybe better options available, but this Silnylon tent has given me more joy than the other three tents I own, which means I can put up with a little misting, condensation and careful set up.

  5. Your apples-to-apples comparisons are really helpful. Without your tabulation, I would not have focussed, for example, on how much more water resistant the DCF ZPacks Duplex is compared to the Tarptent Aeon Li. Of course, I rarely find that a tent gets wet inside from straight rainfall. It is usually from condensation combined with wind blowing water under the fly. So, where and how you pitch the tent, as well as the architecture of the structure matter at least as much as materials. I’d enjoy learning more from you about the differences between silnylon and pu-coated nylon.

  6. Thanks for sharing the numbers and info on waterproofness… below are a few additional comments for consideration:

    > The numbers given are lab numbers based on a certain testing method which may or may not correlate with actual field use. The key point is these numbers represent the pinnacle of the product’s performance, i.e., generally speaking, the fabric tested is from a roll of unused fabric which has not been made into any sort of product. In other words, the performance of the fabric itself is only going to degrade from this point on, depending on actual field use.

    > PU coatings in general can degrade quickly when improperly stored while wet or exposed to chemicals such as DEET or other solvents. They are also subject to wet flex abrasion (primarily garments) and cold crack when temperatures fall below 0 degrees F.

    > According to Natick, the Army has determined that a 165 lb person exerts 3 psi when sitting and 16 psi when kneeling, which is considered worst case scenario. Fortunately, the tests for water entry pressure in psi correlates directly to the water column test in mm’s, i.e., either multiply or divide the number by 700 to get an approximate correlation – in other words, if a coated fabric has a test rating of 10,000 mm, then the correlation in psi’s is approximately 14 psi.

    > Generally speaking, a combination of silicone/PU works best since the PU allows the product to be durably seam taped on the underside while the silicone acts as a ‘super DWR’ on the other side. If you go by lab tests results, then DCF is the ideal product. However, given the incredibly high cost of the product and relative difficulty in working with the product in manufacturing, the price/value relationship is tilted heavily toward a sil/PU product.

  7. Although a temporary condition, Silnylon will absorb water if wet for many hours. I put a standard double wall two person tent out in the rain for about six hours. It gained 15 oz. sone of which is surface tension and maybe not actual absorption but that was after shaking off and stowing ready for a pack. Dynema does let go of water more easily
    Not a big deal since we all dry a wet tent at the earliest opportunity. Just mildly interesting

    • You really have to be careful about lumping all silnylon together. That’s kind of the point of this article. Different grades and coatings behave very differently. Precision is useful. For example, what tent? What was its factory hydrostatic head? How much wear and tear did it experience before your test? And so forth.

      • Good points all. I did it out of curiosity and it was only based on the impression that a wet tent fly was noticeably heavier and that my Dyneema membrane tent did not seem to change much
        The tent was a Kuiu two person mountain tent which is fairly conventional

  8. langleybackcountry

    What I would like to know is how the numbers correlate to actual rainfall, since it is rare to have a 3 meter column of water over my tent fly. :)

    I can say the 3000mm is “more” waterproof than 1500, but if 1500 exceeds what rain will be capable of driving into the fabric the difference is kind of moot.

    • Good point. But keep in mind it’s just a lab test with all the real-world limitations that entails.
      1000 mm will withstand light showers. 2000 mm will withstand heavy rain. Your guess is as good as mine to what counts as “light showers” and “heavy rain. I’ve also seen reference to 2000mm as the level in which water can penetrate a tent floor when someone is sitting on it in a puddle. In general, a higher water column is better.

  9. Camping with a group,one of our participants with one of the group members with a light silnylon group had to spray her tent with a spray to improve the water proofness of the tent. There must me an issue, if they have to sell a spray to fix the problem. Stuff stunk badly too.

  10. There shouldn’t be any problem in expanding your future article on lab tests data to other lab tests which are seen as the ‘holy grail’ of fabric performance, i.e., MVTR tests.

    The one point that keeps getting overlooked or hidden in the marketing spiel is that lab tests are used primarily for quality control in the manufacture of fabrics for use in the outdoors and other end uses. In contrast, marketing departments love to throw around the ‘fact’ that ‘our numbers are better than your numbers’, all of which is bogus and misleading since it has no correlation to a product’s performance in the field. The best example is the MVTR test data that gets spewed around as if they had invented ‘a revolutionary new fabric’ (See: TNF Futurelight). To start with, there are at least 10 different MVTR tests used in a variety of uses, i.e., upright cup, inverted cup, etc. So which tests is most relevant to field performance? Answer: NONE. Why? because MVTR tests are used as a quality control test which are run under strictly controlled climatic conditions (humidity level, temperature, etc) so that they are comparing apples to apples when testing different batches of fabric. Once one of the variables change (as they do in the outdoors constantly), the rate of moisture vapor transfer also changes which in turn invalidates any previous claims.

    • That’s probably a test I won’t cover because I consider the entire concept of rainjacket breathability to be completely bogus bullshit in real-world conditions, as you confirm.

  11. Re: “Tarptent Aeon Li 8,000 mm 8,000 mm Dyneema DCF”, that isn’t quite accurate. We list “8,000mm +” because our pressure tester doesn’t go higher than 8,0000mm. We actually don’t know what the ultimate higher end is because we can’t test it but “more that enough” is certainly accurate.

    • Might want to ask your DCF supplier what their tests show…or get them to buy a machine to prove their quality control to you. :-)

  12. Philip,

    The ratings between materials used by various manufacturers. I would appreciate your insight into what is a ‘minimum’ water resistance rating. I appreciate so many other factors come into play but when one compares a Copper Spur and a Zpacks Duplex the Duplex appears much superior for water resistance. Is it?

    Is the scale a linear scale? It would be informative to add this information.

    • Couple of responses/comments:

      Please remember that the manufacturers are self-reporting these numbers….there’s no outsourced lab certifying them…

      Water-resistance is just one variable. You’d probably want to factor in UV, abrasion resistance, and zipper durability as well.
      For example, as soon as you use your tent it will experience some bottom abrasion and lose a portion of its water resistance.

      What’s the minimum water-resistance I’d recommend for a new (unused) tent? 2000 mm is a good baseline, although 3000 mm is better.
      Consider this. Which tent manufacturers want to sell you a tent footprint? Big Agnes, MSR, NEMO, Gossamer Gear. Is it to cover up a potential point of failure?

  13. On both my silnylon Tarptents (Moment DW and SCARP 2) I have coated the flys with more silicon in a 5:1 mix by volume of 5 parts odorless mineral spirits to 1 part GE clear silicone caulk. It’s mixed by shaking vigorously in a plastic jar then poured into a small pint roller tray and applied in 2’x 2′ section to the pitched tents with a 6″ short napped roller. It is immediately wiped down with heavy duty paper “shop towels” and dries for two days before storage. The same procedure is used for the floors.

    I did this before I found out that Tarptent had increased their silnylon hydrostatic head otherwise I would have only coated the floor exteriors for wear reasons.

    I’m happy to see the very high hydrostatic head for my TT Notch Li DCF tent but I knew it was much higher than silnylon, just not how much higher.

  14. Hike the Planet!

    I tested a Silnylon tarp by draping it over myself in a hot shower. Lasted about 20 minutes before I noticed some water getting through. Could have just been the sweat and steam, though.

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