Two South African companies say they will put the finishing touches on a seven-story building expansion constructed with hemp blocks later this year.

Hemporium and Afrimat Hemp, both of Cape Town, partnered to raise an existing conventional five-story building, 84 Harrington Street, to 12 stories by adding levels constructed with blocks from Afrimat Hemp.

The cost of U.S. construction timber is skyrocketing, and a national concern is growing for the carbon emitted by the construction industry. As homebuilders look for solutions, the nation’s small-but-growing number of hemp builders wonder if building with hemp will finally break through into the mainstream construction consciousness.

Pennsylvania-based hemp building pioneers CoExist Build have released a build-it-yourself 140 sq. foot hemp cabin that can be used as a home office.