This house, in Tarpon Springs, looks just like many others throughout the Sunshine State. But don’t let its benign appearance fool you. This single-family home is unique (so far) in Florida. / Bob Clayton

 

Bob Clayton can boast about something that no other resident of the Sunshine State can (though he wants to change that).


Clayton moved into his new home – made of “hempcrete” – in 2014. No one else in the state is known to have built a house composed of the hemp plant’s woody core and a lime-based binder.

This hempcrete brick was made with hemp shivs, lime (as a binding agent), and water. Hemp shivs, also called “hurds,” are the woody, inner part of the hemp stalk that is left over when the bark fiber is removed. / J.D. Vivian

This hempcrete brick was made with hemp shivs, lime (as a binding agent) and water. Hemp shivs, also called ‘hurds,’ are the woody, inner part of the hemp stalk that is left over when the bark fiber is removed. / J.D. Vivian

In almost every way, the home is like any other. “It meets all building codes, and it will take 175-mile-an-hour winds,” he said. “The building inspectors were very tight on this house.”

Once dry, the hempcrete, though much lighter than concrete, has a similar color and feel.

The hempcrete was poured into special forms, onto the house’s 2-by-6-inch wood studs. Then the area was covered for about a week, Clayton explained, to protect it from rain, and allowed to dry.

The retired mechanical engineer said that his Tarpon Springs home offers other advantages: “This house ‘breathes.’ That’s very important in Florida.” A 1-inch space between the framing and the interior walls allows air circulation – a major plus in the state’s humid climate, in which mold and mildew can easily thrive.

In addition, termites cannot eat the hempcrete. And, Clayton added, “We dumped 12 inches (of raw hemp ‘shiv’) in the attic. That gives us R30 insulation.”

With fiberglass batts and 2-by-6-inch walls, you can get up to R19 or R21 insulation levels. Clayton said his electric bill, in August, is about $90. The walls of the home are 12 inches thick.

The process

The hemp shiv – the loose particles at the center of the plant – are mixed with lime because it binds with the silica in the hemp, Clayton explained.

Hempcrete wall at Bob Clayton's home, under construction. / Courtesy Bob Clayton

A hempcrete wall at Clayton’s home, shown while under construction. / Bob Clayton

Because no chemicals – such as formaldehyde or VOCs (volatile organic compounds) – are used in hempcrete, the house should reduce the potential for allergies.

Clayton imported about $65,000 worth of hemp shiv and lime binder from England. Used in constructing buildings throughout Europe, especially in England, hempcrete weighs only about one-seventh what concrete does.

The forms can be removed in about one hour after pouring the hempcrete, reducing construction time and expense.

The three-bedroom, two-bath house has 1,532 square feet of living space, according to the Pinellas County Property Appraiser’s Office. Total square footage, with the porch and garage, is 2,290. The “just/market value” of the home is $157,987 in 2016, according to the appraiser’s office.

Clayton’s goal

Though highly optimistic about the future of hemp in construction (and for other uses, including agricultural), Clayton admits “The whole house is an experiment.”

His home looks like many other Florida homes built of concrete block. That was an important consideration, since he’d like to see many, many more such houses throughout the state. “I wanted to design a house that could be built in gated communities.”

Bob Clayton, who built Florida’s first house made of hemp, speaks to a visitor about the virtues of hemp at the Fort Pierce City Marina on June 12, 2016. He was in the Florida Cannabis Action Network’s tent. J.D. VIVIAN

Bob Clayton, who built Florida’s first house made of hemp, speaks to a visitor about the virtues of the plant at the Fort Pierce City Marina in June. / J.D. Vivian

One problem with mass production of hempcrete homes is their higher costs for materials. Clayton didn’t keep track of all the expenses while building his unique home, so he cannot compare the construction price of his house to that of a conventional one.

“My house is a prototype. I just had to bite the bullet and pay rare prices to get unusual materials. Often, we had to buy a pallet of material to use a couple bags and throw the rest in the Dumpster.” That’s because, Clayton explained, he and the builders weren’t sure how much they would need, so they sometimes ordered too much of a certain material.

Once production of such homes increases, however, and more construction workers are trained in installing and maintaining hempcrete, prices will drop, Clayton believes.

But that won’t happen until materials don’t have to be imported, he said: “Hempcrete won’t be cost-competitive until we can grow and process it locally, so the ban on hemp farming is keeping this sustainable housing from Floridians.”

J.D. Vivian serves as a writer, photographer and editor for Florida Food & Farm. He has written, and shot photos for, The South Florida Sun-Sentinel, The Palm Beach Post and other publications during his more than four decades in South Florida.