Wooden GH, a question on keeping it from rotting.

I was given a wooden greenhouse for grad from hort school, of course wood is not the best when it rains for most of the year here.
I used to strap a tarp over the top on a dry day in fall, to keep the water out, realizing humidity just comes b/t the glass and tarp. I don't want it to rot, aside from buying another, any suggestions?
Oh- I did cure it with preservatives but it is still going slimy.
Thanks!

Have you got a fan in there Dennis? Is it vented?

Something I forgot to mention, it is 6' x 12', and has 3 automatic vents, because we get several sunny days in winter where it is hot inside and O'c outside.
Thanks

The tarp might be the worst thing you can do. It will add another layer to trap moisture. Find out what kind of wood its made of, cypress. redwood or ceder won't rot. Some of the new treated ones may have been used. Good luck!
Bernie

the one i have is about 60+ years old and was built by my grandfather. it is in "ok" shape it needs something every year at this point it is about 19x23

Thanks everyone, Liz I don't have a fan in there, just the heater. Guess what's going back in this minute? It will also likely stop my sanguineas buds from dropping. CG it is either redwood or cedar (probably cedar because it's our most common native tree here and local built), people build treated cedar fences here and they last on average 12 years in this damp mild climate. That's why I wonder. I'll start with a fan. When I move I will be dismantelling it, and before it goes back up I'll be sanding (arg) and re treating, and then varnishing. Where I'm going it is colder drier winters, and hotter drier summers, which should help.
Thanks, Dennis