The government does not back du Plessis' ideas
Houses made from cannabis are far stronger and cheaper than conventional buildings, says South African innovator Andre du Plessis.
He sees this as the solution to the housing problem in South Africa, where millions of people live in shanty towns.
Since he started advocating the "dope houses", some South Africans have been joking that if one caught fire, people would run towards the burning building, rather than away.
But Mr du Plessis told the BBC Network Africa programme that if one of the houses did catch fire, it would not give off any "class C or D noxious fumes".
So he says people would have no reason to steal lumps out of the houses to smoke.
The fibre from the cannabis plant, which used to be used to make ropes, would be mixed with lime and sand.
Millions of South Africans lack proper housing
"It looks like cement - a brownish, greyish hue," he said, adding that it would not smell of cannabis.
Although Mr du Plessis says the cannabis cement is six times stronger and six times cheaper than normal cement, the South African Government is not interested in his idea.
He says he has 30 or 40 letters from different government departments saying "Thanks, but no thanks".
"It's quite frustrating when you're suggesting something that can only aid South Africa. I'm not doing this for any personal gain."
He also argues that building houses from cannabis cement would create lots of jobs for South Africans growing the marijuana.
Three tons of cannabis mixed with lime and sand would be needed for each house.
The houses would not give off any noxious fumes, even if set alight
Mr du Plessis says they would cost about 15,000 rand ($2,000) for an 82 square metre dwelling.
And where did he get the idea?
"I was unemployed and I was busy looking at the greater problems of South Africa, in particular land and housing," he says.
He has built a model dome about 50cm high.
"As yet, I haven't managed to source enough cannabis to build a full-scale prototype," he said.