If you need high strength to support the roof/deck over the columns, white oak is an excellent choice. However, if the reason for replacement is bug damage (i.e. termites, carpenter ants, etc), then cypress will outlast white oak. If you are wrapping existing support columns, I would use cypress. Bug/weather resistant. Easy to work with. Holds paint well without the oil/stain problems of redwood and cedar (I would use a latex paint. Oil base will peel/flake unless you thoroughly seal all surfaces, inside and out).
JMTCW
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