Home Postcode finder SA Sheaoak Flat Sheaoak Flat postcode SA Sheaoak Flat is a locality in South Australia covered by postcode 5581. Postcode 5581 State or territory South Australia (SA) Region Sa Subs Near 1 Add a free Sheaoak Flat business listing Be the first listing in Sheaoak Flat Common questionsWhat is the postcode for Sheaoak Flat?Sheaoak Flat, SA has the postcode 5581.What state is Sheaoak Flat in?Sheaoak Flat is in South Australia (SA).Does postcode 5581 cover more than one suburb?Yes. Postcode 5581 covers 2 localities, so the postcode alone does not identify Sheaoak Flat. Browse other postcodes in South Australia, or widen the search to every Australian postcode.