Previous blog posts have explained how earthbag homes are similar to rammed earth (see Ancient Rammed Earth Structures) and compressed earth (see Impact Testing Megablocks with Black Powder Cannon). And in comparison to adobe, which is also quite durable, earthbags gain additional durability from:
– Tamping (greater density, less air space, clay platelets bonded together)
– Barbed wire (added tensile strength)
– Soil is contained in strong bags that will likely last hundreds of years when protected from ultraviolet exposure. See Durability of Polypropylene Bags where it quotes “A Federal Highway Administration (FHWA) study concluded that the half life of polypropylene fabrics in benign environments could be 500 years or more.”
So there is abundant and compelling evidence that indicates earthbag houses protected with plaster and properly maintained should last hundreds if not thousands of years.
However, earthbags are vulnerable to UV damage if left unprotected for more than a few weeks during construction. This topic was addressed in a previous blog post How to Reduce or Eliminate Tarping Earthbag Walls. The simplest solution is to slosh or spray a thin coat of mismatched recycled latex paint on the bags. It’s really cheap in five gallon buckets, especially during close-out paint sales and on Craigslist. You might even get it free at community drives that collect hazardous household goods.