Was helping my folks to build a pergola, we dug holes about 60cm deep, placed piece of brick at the bottom then planted the timber posts in and poured quickset concrete mix to about 15cm from the top.
Some visiting relative was saying we should have concreted all the way to the top or the base of the posts will rot over time because they are buried unprotected.
Is that true? I thought concrete was used for structural purpose only? Should we pour more concrete?