A sticky tent is a polyurethane coating breaking down by hydrolysis. Water splits the polyester links in the coating, and what was a smooth waterproof film becomes a soft, tacky one that smells and starts to flake. It cannot be reversed. You can strip the failed coating and paint on a new one, or replace the fly, but the stickiness itself means the waterproofing is already going.
What makes a tent sticky?#
Tent fabric is usually woven nylon or polyester with a waterproof coating. When the outdoor trade says "PU", it means polyester urethane, a polyurethane whose soft segments are built from polyester. That is the chemistry that goes sticky.
The weak point is the ester link. Czeiszperger's review of polyurethane hydrolysis gives the order of resistance as "ester<<urea<urethane", and says the hydrolytic stability of the alternative, a polyether, "is excellent". Each link water breaks shortens a chain, and the coating loses strength and cohesion.
Sandia National Laboratories watched it happen. A polyester urethane held at 80 and 95 degrees C at 100 percent humidity started as "semi-rigid pellets" and "converts to a viscous, tacky substance during the aging process". NMR spectra of the aged material showed new carboxylic acid and alcohol groups: the two halves of the broken ester.
Many tents are sil/PU: silicone on one face, PU on the other. The tent maker's guide published by Garage Grown Gear explains why. Silicone sheds water better, but the PU side is where the fire retardants go to meet CPAI-84, the old American tent flammability specification covered in why tents carry a flame warning. The PU side is usually the inside. So on a sil/PU fly, the outside can still bead water perfectly while the inside has turned to glue.
Is it hydrolysis, or something else?#
Not every tacky tent has a failed coating.
| What you notice | Most likely cause | How to check | What to do |
|---|---|---|---|
| Inner face of fly or top of floor tacky, sticks to itself when folded | PU hydrolysis | Fold the face onto itself, press, peel | Strip and recoat, or replace the fly |
| Sour, musty "old tent smell" that a wash does not remove | PU hydrolysis | Smell the coated face, not the mesh | Same as above |
| White or grey flakes on the floor, or the coating peels in sheets | Advanced hydrolysis | Rub with a thumb: flakes come away | Strip completely before any recoat |
| Black or coloured spots, often in folds, plus a damp smell | Mildew | Spots in patches where the tent lay folded and wet | Clean and dry; the coating may be damaged under it |
| Tack only along the seams, a few days after sealing | Uncured seam sealer | Recent seam sealing, tack follows the seam line | Let it cure; dust with talc |
| Seam tape lifting or peeling in strips | Tape adhesive failure | Edges of tape curl away from the fabric | Reseal the seam; separate from the fabric problem |
GEAR AID lists three signs that a factory PU coating needs replacing: "a foul odor", peeling or flaking, and "a sticky or gummy feeling". The Garage Grown Gear guide calls the smell "Old Tent Smell" and puts it down to hydrolysis. It also warns that "humidity alone can destroy coated fabrics and factory hot-taped seams", so a sticky fly and peeling tape often arrive together and need both jobs done.
If both faces of the fabric feel slippery, the tent is sil/sil (silnylon or silpoly) and the cause is not PU hydrolysis. The same guide says "silicone coatings don't hydrolyze".
Why it seems to happen all at once#
When an ester link breaks, one of the products is a carboxylic acid, and acid catalyses ester hydrolysis. Each broken link makes the next break more likely. Czeiszperger measured it in the water the samples sat in: water that started at pH 7.76 finished at 5.47 and 5.76 for the two polyester polyurethanes, and rose to between 8.98 and 9.08 for the polyethers, which release basic amine groups instead of acid.
Sandia saw the timing. Changes in the polymer's mobility were "modest" until 4 weeks at 80 degrees C and 2 weeks at 95, then fell sharply, which "suggests an autocatalytic response due to production of carboxylic acid". In Czeiszperger's own tests at 50 degrees C, the polyester samples kept their tensile strength "very well for about two months", then dropped "dramatically".
So a tent that was fine one season and sticky the next is the expected shape, and a coating tacky in one corner is not stable: it is further along the same curve as the rest of the fly.
How much faster heat makes it: the storage arithmetic#
Most care advice, including our own gear storage guide until today, uses the rule of thumb that reaction rate doubles for each 10 degrees C. For polyester polyurethane the measured figures are steeper.
Czeiszperger's review cites Gajewski (1989) for half-lives at two temperatures: a polyester-based system fell from 4 to 5 months at 50 degrees C to 2 weeks at 70. That is a rate ratio of about 8.7 to 10.9 across 20 degrees. Putting those two points through the standard Arrhenius relationship gives an activation energy of about 100 to 110 kilojoules per mole, and from that a rate at any storage temperature. This is our arithmetic on two published numbers, and it is a model.
| Where the tent spends the summer | Temperature | Ageing rate against a 20 degrees C cupboard | Doubling rule says |
|---|---|---|---|
| Cool basement | 10 degrees C (50 F) | 0.20 to 0.24 | 0.5 |
| Cupboard in a heated home | 20 degrees C (68 F) | 1 | 1 |
| Warm room | 25 degrees C (77 F) | 2.0 to 2.1 | 1.4 |
| Hot room or shed | 30 degrees C (86 F) | 3.9 to 4.4 | 2.0 |
| Loft under a roof, summer afternoon | 35 degrees C (95 F) | 7.3 to 9.0 | 2.8 |
| Loft or shed in a heatwave | 40 degrees C (104 F) | 14 to 18 | 4.0 |
| Closed vehicle in sun | 50 degrees C (122 F) | 45 to 66 | 8.0 |
Every 10 degrees C near room temperature costs a factor of about 3.5 to 4.5. A week in a car at 50 degrees C does about as much hydrolysis as 10 to 15 months in a 20 degrees C cupboard, where the doubling rule would say 8 weeks. A basement at 10 degrees C ages a coating four to five times more slowly than a 20 degrees C room.
Can a sticky tent be fixed?#
Not by reversing it. The Garage Grown Gear guide is blunt: "once hydrolysis has begun, there's no stopping it", and a scrub that removes the smell is "a purely symptomatic treatment". What you can do is remove the failed coating and replace it.
The decision, in order:
- What is the fabric? Check the spec sheet or label. If it is sil/sil, the problem is not hydrolysis; go back to the table above. If it is PU, sil/PU or PE, carry on. Silicone-only fabric cannot take a PU recoat: GEAR AID says its PU sealer "will not work on silicone-treated fabrics nor sil-nylon".
- Is a replacement fly sold? A new fly brings a factory coating and taped seams. A recoat leaves the seams to you.
- How much of it is gone? Tack in patches or across the whole inner face is a strip-and-recoat job. Strip the whole panel, not the patch: GEAR AID says "it is important to remove the previous coating" before applying a new one, and the autocatalysis above means the rest of the panel is not far behind.
- Are the seams failing too? If tape is lifting along most seams as well, you are taking on two full jobs. That is the point at which retiring the tent, or keeping it for fair-weather car camping, is a reasonable call.
After a recoat, treat the fly as waterproof only once it has passed a hose or bucket test. A factory coating comes with a hydrostatic head rating of the kind described in waterproof ratings explained; your own coat does not.
How to strip and recoat a sticky fly, step by step#
From GEAR AID's instructions and the Sierra Designs and SylvanSport support articles. Where they differ, both are given.
- Soak. GEAR AID: a tub of warm water with "about 5 drops of liquid soap", item submerged for 2 to 3 hours. Sierra Designs: cool water with unscented laundry detergent, unscented because "scents can attract skunks, bears, and other animals".
- Scrub the coated face (fly underside, floor top) with a mix of isopropyl alcohol, water and a couple of drops of soap (GEAR AID). For stubborn patches, Sierra Designs says rubbing alcohol "dissolves the urethane into a greenish blob that you can scrape off".
- Rinse, dry completely, and brush off remaining flakes, as Sierra Designs and SylvanSport both advise.
- Apply one thin film of a PU tent fabric sealer to the coated face only.
- Dry for at least 4 hours at room temperature with treated surfaces kept apart, then dust with talc "to alleviate any surface tack" (GEAR AID).
- Seal the seams, with a silicone-based sealant on silnylon. GEAR AID gives cure times of 2 to 12 hours depending on the sealant.
- Renew the outside water repellent if water no longer beads, and let everything dry at least 24 hours before storage (SylvanSport).
Work outdoors or with the windows open when using alcohol, and keep it away from flames.
Check this before you store a tent, or buy one#
- Find the coated face. Fly underside, floor top. Note whether the label says PU, sil/PU, PE or sil/sil.
- Smell it. Put your nose to the coated face of the fly and the floor, away from the mesh. A sour smell that survives airing is the first sign.
- Press and peel. Fold a section of the coated face onto itself, press it with your palm for ten seconds, and peel it apart. Healthy coating separates cleanly; failing coating clings or sheds flakes.
- Bowl test the floor. Hold a section of floor as a bowl, pour in a litre of water and leave it for ten minutes. Damp patches on the underside show where the coating has gone, as with the seam check in reproofing rain gear. Water inside the tent after a night out is usually condensation, not this.
- Store it dry and cool. Bone dry, loosely packed, and in the coolest dry room you have. The table above is the reason.
If you want a tent that outlasts hydrolysis, fabric matters more than brand. The Garage Grown Gear guide says it almost never sees hydrolysed polyether (PE) coatings and has "never seen a sil/sil fabric go bad". Our guide to choosing a tent compares polyurethane and silicone coatings as a buying decision.
Common mistakes#
Dusting it with talc and packing it away. Talc stops the fabric sticking to itself. The coating under it is still breaking down and still losing waterproofing.
Recoating over the old coating. New sealer on a tacky, flaking surface bonds to the failing layer, not to the fabric. Strip first.
Putting PU sealer on silnylon. It will not adhere. Silicone fabric needs silicone products throughout.
Stripping only the sticky patch. The rest of the panel is the same age and chemistry, and the acid from the failing area is right next to it.
Storing the tent in a car, shed or loft between trips. At 40 degrees C the model above puts ageing at 14 to 18 times the rate of a cool cupboard.
Frequently asked questions#
Why does my old tent smell so bad?#
The smell comes from the same reaction that makes the coating sticky. Water breaks down the polyester polyurethane coating on the inside of the fly and the top of the floor, and the products give old tents a sour, musty odour that airing does not clear. GEAR AID lists a foul odour as one of the three signs that a factory PU coating needs stripping and replacing, alongside stickiness and flaking.
Can I just put baby powder on a sticky tent?#
Talc, the usual base of baby powder, stops a tacky coating sticking to itself, and GEAR AID recommends dusting a freshly recoated surface with it. On a hydrolysed coating it treats the symptom only: the coating underneath is still breaking down and losing its waterproofing. Use powder as the final step of a strip and recoat, not instead of one.
Is a sticky tent still waterproof?#
Sometimes, for a while. Stickiness means the coating has started to break down, and Sierra Designs groups sticky, flaky and leaking as stages of the same failure. A sil/PU fly can still bead water on the outside while the inside is tacky. Test it with a hose or a bowl of water before a trip that depends on it, and plan a recoat or a replacement fly.
How long does the PU coating on a tent last?#
Sierra Designs says breakdown generally starts at around 8 to 10 years and recommends retreating every 8 to 12 years. Storage decides where in that range, or outside it, a given tent falls. Heat speeds hydrolysis by roughly 3.5 to 4.5 times for every 10 degrees C, so a hot loft or car pushes a tent toward the early end of that range and cool, dry storage pushes it the other way.
Do silicone-coated tents get sticky?#
Not from hydrolysis. Silicone is far more chemically inert than polyurethane, and a tent maker writing for Garage Grown Gear says silicone coatings "don't hydrolyze". Some tents described as silicone-coated are actually sil/PU, with polyurethane on the inside face, and that inside face can go sticky. Check the spec for "sil/sil" or "silnylon" before assuming your tent is immune.
Is a sticky tent covered by warranty?#
Usually not. Sierra Designs states that coating breakdown "is not covered under warranty" because it is part of a tent's natural ageing, and SylvanSport describes it as normal wear. It is still worth asking the maker whether a replacement fly is sold, often the simplest fix when the poles, floor and zips are sound.
Standards, sources and further reading
- Lang, D. P., Assink, R. A. and Celina, M., *Chemical and physical changes in a hydrolyzed poly(ester urethane)*, Sandia National Laboratories, OSTI 15017. A polyester urethane aged 2 to 8 weeks at 80 and 95 degrees C under 100 percent relative humidity turned "viscous" and "tacky"; carboxylic acid formed and the delayed onset "implies an autocatalytic degradation mechanism".
- Czeiszperger, R., *Polyurethane Elastomer Hydrolytic Stability: A Comprehensive Review*, Anderson Development Company, Polyurethane Manufacturers Association conference, 2012. Ranks ester, urea and urethane links for hydrolysis resistance, reports the pH of immersion water, and cites Gajewski (1989) for half-lives at 50 and 70 degrees C.
- Sierra Designs, *My tent is sticky, flaky, and leaking water: what do I do?*, support article. Onset at around 8 to 10 years, the strip and retreat procedure, and the warranty position.
- SylvanSport, *When your tent becomes sticky or the coating flakes off, the urethane coating is starting to break down*, support article. The same procedure, which product goes on which face, and drying time before storage.
- GEAR AID, *Tips for Using Seam Grip TF*, application instructions. Signs that a factory coating has failed, the soak and alcohol removal method, drying time, talc, and that the product does not work on silicone-treated fabric.
- GEAR AID, *How to Waterproof and Seam Seal a Tent*, 2020. Seam sealant cure times and silicone sealant for silnylon.
- Garage Grown Gear, *Tent Fabric Coatings: Pros and Cons of PU, PE and Silicone*, written from a tent maker's perspective. What "PU" means in the outdoor trade, sil/PU construction, the hydrolytic stability of PU, PE and silicone, and humidity damage to taped seams.
- MSR Xtreme Shield technology page, as reproduced by Ultralight Outdoor Gear. A manufacturer's claim of a coating "3 times more durable than standard coatings", with no test method given.
How this page is made. Every number here is either a published standard, a physical constant, or arithmetic we show in full so you can check it. Read our evaluation method and editorial standards, or tell us we got something wrong.
Last reviewed and updated 6 October 2026.