New Hempcrete Wall Technique Cuts Drying Time in Half

Pre-cast hempcrete blocks from Co-exist Build will be used in combination with a spray applied hemp+lime application on two dwellings in New York this spring.

By Jean Lotus

Three pioneering companies in the emerging U.S. hemp-building industry will collaborate this spring on two projects that will use multiple hemp building techniques.

Two vacation cabins in New York’s Hudson Valley will use precast hemp-lime blocks on inner walls and spray-applied hempcrete insulation on outer walls to minimize the projects’ cure time, said Jennifer Martin of Goshen, Mass.-based HempStone, which is serving as general contractor on the project.

“The clients want to keep the construction schedule moving forward and not have to wait,” for inner walls to cure, Martin said. While the outer walls are drying, lime plaster can be applied to the inner walls, she added.

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The precast hemp blocks were developed by the husband-and-wife design team at Western, Pa.-based Coexist Build.

Co-founders Drew Oberholtzer and Anastasiya Konopitskaya received a $75,000 grant from the Pennsylvania Department of Agriculture to design the construction blocks, which are the same size as CMU concrete blocks, although much lighter in weight. As with regular masonry, blocks are attached to structure frames with brick ties like a traditional facade system, Konopitskaya said.

The blocks are manufactured with hemp grown in Pennsylvania and lime sourced locally in an economic model inspired by the restaurant farm-to-table movement.

The company seeks to create a “completely in-state supply chain for the hemp industry and distribution line,” Konopitskaya said.

Meanwhile, on the outside of the structures, Cameron McIntosh and Allenstown, Pa.-based Americhanvre Cast Hemp will use spray-applied hempcrete to create a thermal envelope on the outer walls. Those walls can later be plastered with lime stucco after they cure in about six weeks.

Consultation for the project has been by Alex Sparrow, of UK Hempcrete, who has been designing and building with hemp in Great Britain for more than a decade.

General contractors HempStone, led by Martin and partner Tom Rossmassler, have been designing and building with hempcrete and other natural materials in New England since 2018.

The company recently oversaw the hempcrete installation of the Goshen Howland Hemp House, a traditional timber frame home built by Village Carpentry, a family-owned building and landscaping business. The family carpentry company is now making hempcrete wall panels.

Jean Lotus is editor and publisher of HempBuild Magazine. jeanlotus@hempbuildmag.com