Tad late to the party but I use core wood structures for the pillars below. They are a lot more sturdy and stable. According to ♥♥♥♥ they do not degrade past 50%. Glad to have learned that. Makes sense given the abandoned wood structures in the Meadows never go away from weather. The following screenshot shows what I mean regarding the bridge I built:

https://prnt.sc/15v88s5

Regardless, a good roof over the stairs and bridge itself just high enough to drag a cart by is good for me. Gotta do fetch quests with Copper across a river given the only good source of them is past a river and I need me a lot. Gotta flatten the edges of the other side first given its a mountainside to go past. Hope this image helps