If you are buying a site and entering a contract to have a house built on that site, you are treated as if the entire contract is for the purchase of the property and the stamp duty is applied accordingly.
If you are building yourself, then there is no stamp duty on the house part but there is stamp duty on the site (the 80k is not under the limit as the site is not residential property and would be subject to stamp duty at 5%).
If you are building yourself, then there is no stamp duty on the house part but there is stamp duty on the site (the 80k is not under the limit as the site is not residential property and would be subject to stamp duty at 5%).