ground cloth is getting very sticky. Worth washing with detergent and retreating?
Sticky from forest detritus or sticky because the waterproofing is breaking down? I've had to toss two tents due to the latter. One was warrantied by Nemo, great company, one was a write off.
On 15 and 20 year old rain flies from two different tents, a Nemo and a North Face, I've had the stickiness problem, which then progresses to flakiness. In both cases it was the waterproof polyurethane (PU) coating delaminating and breaking down. Nothing to do with sap or forest detritus.
PU delamination can be accelerated by storage while damp or storage in hot places. But even when stored ideally, the PU coating may have a useful life of only 8-10 years. Maybe you can wash and scrub off such chemical stickiness, but that seems unlikely to restore the waterproofness. Restoring waterproofness would require stripping off the old, cruddy PU coating and recoating the fly or ground cloth with some sort of PU or silicone sealant.
In one case the tent was Nemo Losi 3P, and as they did for
@Tryin', they honored their lifetime warranty by offering me a brand new $600 tent or a $400 purchase credit on their site.
Some people like to do different projects to revive different things. Not me, usually. I had no interest in trying to chemically revive my North Face Slickrock rain fly, so I use the old sticky fly as a snow cover for my tractor cockpit in winter. (I no longer had a proof of purchase for my North Face, so I never tried a warranty claim.)
I have three much older tents that I haven't looked at in 25 to 40 years. I have no idea of their condition. Maybe I'll peek someday out of curiosity. Meanwhile, I'm happy with my brand new REI Halfdome 3P, using my uncoated Nemo "Pawprint" as an inside-the-tent floor cover.
If it were me, which no one else is, and I had a good tent but a stickily delaminating outside ground cloth, I'd just make or buy a new one. Cutting a plastic ground cloth is cheap and easy. And no coatings to worry about.