Silnylon and silpoly are the two fabrics most ultralight tents use. They look similar, weigh similar amounts and both need seam sealing — so why do some tents use nylon and others polyester?
The short answer: silnylon is lighter and packs smaller, but it stretches when wet. Silpoly is slightly heavier for the same strength, but it sags less in rain and handles UV better. For UK conditions, that difference matters.
Silnylon or silpoly — which is better in rain?
Quick answer: Silpoly is the better choice for UK rain because it absorbs less water and sags less when wet. Silnylon is lighter and packs smaller, but it can lose tension in sustained rain. Both need seam sealing unless factory-sealed.
Silnylon vs silpoly at a glance
| Property | Silnylon | Silpoly |
|---|---|---|
| Base fabric | Nylon | Polyester |
| Weight | Lighter for the same strength | Slightly heavier |
| Stretch when wet | Noticeable; fly can sag | Low; pitch stays tighter |
| Water absorption | Absorbs a little water | Absorbs very little |
| UV resistance | Good, but lower than polyester | Better |
| Pack size | Smaller | Slightly larger |
| Seam sealing | Required unless factory-sealed | Required unless factory-sealed |
| Best for | Dry trips, fast-and-light | UK rain, long pitches, UV |
What is silnylon?
Silnylon is a nylon fabric coated with silicone. It is light, strong for its weight and packs down small. That is why many trekking-pole tents use it, including the standard Lanshan 1 and Lanshan 2.
The downside is stretch. Nylon absorbs a small amount of water, and the fabric can relax when wet. A silnylon fly that was drum-tight in the garden can sag after a night of rain. You can re-tension it, but it is an extra job in bad weather.
What is silpoly?
Silpoly is a polyester fabric with a silicone or silicone/PU coating. Polyester absorbs very little water, so it does not stretch as much when wet. The pitch stays tighter, which is useful in wind and rain.
Silpoly is usually a little heavier than silnylon for the same tear strength, and it may pack slightly larger. It also has better UV resistance, which matters if the tent is pitched for long periods.
Does silnylon or silpoly sag in rain?
Silnylon sags more. The fly can lose tension as the nylon absorbs water and stretches. Silpoly stays closer to its original pitch. In UK conditions, that is the main practical difference.
Neither fabric is waterproof on its own. The coating provides the hydrostatic head, and the seams need sealing. A 20D silnylon with a 4,000 mm coating can be more waterproof than a cheap 40D polyester with a weak coating.
Weight and pack size
Silnylon wins on weight and pack size, but the difference is small on a two-person tent. If you are counting every gram, silnylon is attractive. If you want a tighter pitch in wet weather, silpoly is the more practical choice.
Seam sealing
Both fabrics need seam sealing unless the manufacturer has already sealed the seams. Silnylon and silpoly seams can both wick water. Use a silicone seam sealer compatible with the fabric, clean the seam, apply a thin layer and let it cure.
Our guide to seam sealing a tent covers the process step by step.
Which is better for the UK?
For most UK backpacking, silpoly is the more forgiving choice: less sag, less water absorption and better UV resistance. If you mostly camp in dry conditions, or you want the lightest possible pack, silnylon is still a sensible choice.
The standard Lanshan 2 uses silnylon; the Lanshan 2 Pro is available in silnylon and silpoly versions. Check the product page for the exact fabric of the variant you are buying.
FAQ
Is silnylon waterproof?
The coating makes it waterproof, but the fabric itself is not. Hydrostatic head depends on the coating and seam sealing, not the name.
Does silpoly sag when wet?
It sags much less than silnylon because polyester absorbs very little water. The pitch stays tighter in rain.
Which is stronger, silnylon or silpoly?
Both are strong for their weight. Silnylon has slightly better tear strength at the same weight; silpoly has better UV resistance.
Do both fabrics need seam sealing?
Yes, unless the manufacturer has factory-taped or sealed the seams. Silicone-coated fabrics usually need a silicone sealer.
Which packs smaller?
Silnylon packs smaller for the same strength, but the difference is small on a two-person tent.
Verdict
Silnylon is lighter; silpoly is more stable in wet weather. For UK use, choose silpoly if you want a tighter pitch and less sag. Choose silnylon if weight and pack size matter more than the last bit of weather resistance.
Still choosing a tent? Start with the Lanshan comparison hub or browse ultralight tents.
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