Re: pvc "lumber"
I have used both Home depot and Lowes PVC trim boards on various properties over the past 10 years. Both still show no indication of chalking or any UV damage, painted or unpainted.
The Lowes material costs more but is solid PVC and can be milled and edge finished. The Home depot material is a low density and only surface finished, milling produces an edge that requires filling and painting, so is best used where an edge is not exposed.
Both products have limited structural properties and will deflect with horizontal clear spans more than 12", or vertical clear spans more than 16".
Both can be glued with polyurethane glues or PVC pipe glue.
1970 Havsfidra 20 by Fisksatra
On the Delaware River at Fox Grove Marina Essington PA