Pretty darn strong, but it’s not concrete – it is a fraction of the weight, and about 1/20 of the compressive strength of concrete. Keep in mind that the hempcrete does not function as a structural component. In our region, we design for seismic zone 2a, and winds loads (typically) of 90mph. With certain limitations, we are able to use cast hempcrete as a shear wall. For a recent project on the mid-Atlantic coast, we designed for seismic zone 2 and 130mph wind loads. These wind loads, significantly in excess of typical specifications, were addressed with engineered steel brace frames at five locations in the exterior and interior walls.
Any construction will require an engineer’s stamp. We are fortunate to have local firms that have worked on a number of projects using hemp and really understand the material.