Silicone-coated nylon is lighter and stronger for its denier and stretches when it gets wet; silicone-coated polyester barely moves and weighs more for the same denier. Everything else about the two — the coating chemistry, the repair rules, the way a pitch behaves — follows from that one difference.
What the two names mean
Both are woven fabrics with a silicone coating, and the shorthand names describe the yarn underneath. Silnylon is siliconised nylon; silpoly is siliconised polyester. Both are quoted in denier, both are used for flysheets and tarps, and both are found across the same weight band on the shelf.
The silicone part is what they have in common and it matters more than most people expect, because it changes what can be stuck to the fabric later.
Stretch is the working difference
Nylon absorbs water and relaxes as it does. A silnylon tarp pitched taut in dry evening air will sag once the rain arrives, and the answer is to retension the guylines rather than to blame the pitch. Experienced users treat that as part of the routine.
Polyester takes up almost no water and holds its dimensions. A silpoly pitch set tight stays tight, which is the argument for it in a shelter you would rather not get out of a sleeping bag to adjust at three in the morning.
The trade is weight and tear resistance. At the same denier, nylon is the stronger fibre and the lighter fabric, which is why the very lightest coated shelters are still nylon.
Both change how you repair them
This is where the choice reaches beyond the pitch. Silicone-coated fabric rejects ordinary adhesive tape. A conventional self-adhesive repair patch will lift off a silnylon or silpoly fly, usually in the rain, because there is nothing for the adhesive to key into.
Repairs on these fabrics need a silicone-specific repair tape or sealant, and the same rule applies to seam sealant. By contrast, a polyurethane-coated flysheet — the third fabric on this shelf, and the one most family tents use — takes the conventional patches and the conventional sealant.
Makers state which coating their tape is for. Read the flysheet label before buying a repair kit rather than after a pole has gone through the fabric, because silicone tape on a PU fly and PU tape on a silnylon fly both fail the same way.
How to read this listing
Four figures make coated fabrics comparable. The denier, which describes the yarn. The hydrostatic head in millimetres, which is the maker’s waterproofness figure for the coating and is published separately for a fly and for a floor. The weight, noting whether the maker is quoting a bare canopy or a complete pack with guylines and pegs. And the coating name itself, which is the thing that decides the repair rules.
Where a maker publishes no denier at all, the fabric is often Dyneema composite — a laminate rather than a coated weave, which does not stretch or absorb water, weighs least and costs most. It is a third answer to the same question rather than a variant of either.
Choosing between them
If the priority is the lightest possible shelter for its strength and you are content to retension after rain, silnylon is the traditional answer. If the priority is a pitch that stays where you put it, silpoly is. Neither is more waterproof by virtue of its yarn: that is the coating’s job, it is published as a hydrostatic head, and it is quoted for the fly and the floor as two separate numbers.
What people ask before buying
Which one holds a taut pitch better in rain?
Polyester, because it absorbs almost no water and barely stretches. A silicone-coated nylon tarp or fly pitched drum-tight in the evening will usually want retensioning once it is wet, which is a known property of the fabric rather than a fault in the pitch.
Can I use ordinary repair tape on either of them?
No. Silicone-coated fabrics reject conventional self-adhesive repair tape and need a silicone-specific tape or sealant. Polyurethane-coated flysheets take the conventional patches. Makers state which coating their tape is for, and the two are not interchangeable.
Last reviewed 6 September 2026