Walipini framing material?

Sorry if this has already been covered on here, but I couldnt find it.

Building a Walipini with concrete block walls but I need a long lasting material for the roof trusses. I've been asking around and it seems that the more I ask, the more opinions I get. I've heard locust, white oak, hemlock, and finally one fella said to use modern copper treated pine. He said the modern treated is safe, and Google says that as long as it doesnt contact the food directly that its safe. Another source suggests regular pine with a penatrating oil, like tung. Then there's the thing of if I miscount or miscut and have to get one or two boards.

I cant get locust (all crooked), hemlock is 1.10 per board foot, white oak is .80 a board foot. Treated is .45 a foot.

I want to build a good structure, but I just cant spend tons of money. I'm looking at around 600 board foot. Perhaps more.

Suggestions and experience?

Thanks.

Our pit-style growhole uses cedar. Has lasted, oh I bet 25 years, but getting pretty light now... Cedar is expensive, but it seems to work OK in that cool, humid environment. Good luck! Best, T

Oh, and I sure wouldn't use any treated wood...

cant get cedar in anything but 1 X somethings at lowes, unless it's trucked in and then I'd pay shipping by truck.

Why wouldnt you use treated? supposedly now its copper napthalate which is only a fungicide.

Hi Matt,

I'm struggling with the same thing. However my greenhouse is currently going to be 40'x55' so the vertical on the roof is 45' based on the pitch I need. Can't find wood that long without it being manufactured. It was suggested to me to use metal tubing. Not sure the cost for you but just a thought.

Jim