A subsea wellhead assembly for a subsea well including a low pressure wellhead housing having a string of conductor piping extending therefrom. A high pressure wellhead housing, having a string of outer casing suspended therefrom, lands within the low pressure wellhead housing. The high pressure wellhead housing has a housing bore. An adapter is positioned within the housing bore. The adapter has an external load shoulder that lands on a housing load shoulder of the high pressure wellhead housing. The adapter also has an adapter bore with an inner adapter load shoulder formed thereon. A casing hanger is carried in the adapter bore, and has a string of inner casing suspended therefrom and is cemented in the well. The casing hanger lands on the inner adapter load shoulder.