“Owen, Found an interesting document I thought you might find interesting. It looks like someone’s thesis.
moisture barrier
Ferrocement Rainscreen for Earthbag Domes
Domes evolved in deserts, so we recommend extra protection for snowy/wet climates. There are two main approaches: 1. Build a roofed dome. Search our Projects pages at Earthbag Building.com to see several examples. 2. Build a ferrocement rainscreen on the exterior of the dome. The rainscreen is basically an outer cement shell that’s built on top of the dome with about 1″ space between that allows any water that gets through to escape.