Engineered flooring shows the possibilities of this fast-growing plant
by Belinda Carr
Hemp stalks are soaked in an adhesive then made into boards under heat and pressure
The resulting product is attractive, durable, non-toxic and fire-resistant
It’s also more sensitive to moisture than some other materials
Social media and the DIY movement have contributed to the growing popularity of natural building materials, eco-friendly products, improved air quality and healthy homes. Hemp is at the forefront of this movement.
Hemp itself is nothing new—as the oldest domesticated crop in the world, it can be traced back to 8000 BC. Unfortunately, the Marijuana Tax Act of 1937 (sold as an anti-drug measure), also blacklisted hemp, even though hemp has a small fraction of the THC (tetrahydrocannabinol) found in marijuana and is not psychoactive.
The heavy tax on hemp sales led to the decline of the hemp industry. The timing of the tax bill was suspicious because it directly helped the emerging plastic and nylon industries gain significant market share.
Things finally changed in 2018 when the Farm Bill legalized hemp and all its derivatives. That has led to some exciting new products, including one I recently looked at called HempWood. It’s an example of how new processes can transform an old substance into a building material that many homeowners will love. It’s something I think a lot of builders—off-site or on-site—could profit from.
How It’s Made
HempWood (some people call it WeedWood) is produced by Fibonacci LLC in Murray, Kentucky. Although some of the processes used to make it are patented, the broad outlines of its manufacture are quite simple.
- Full-length fiber hemp stalks arrive from farmers in bales
- The bales are separated and the stalks spread evenly on a mesh
- The stalks are then submerged in a proprietary, all-natural soy-based adhesive
- After saturation, they are spread on racks and placed into a dryer
- After drying, the stalks are weighed into portions and compressed under 3000 tons of pressure into steel molds
- The molds are baked in an oven until the catalyst in the glue is activated
- The result is solid HempWood blocks, which can then be sawn and shaped into finished products
Although HempWood has been used for products that range from guitar bodies to furniture, the product builders will be most interested in is the company’s tongue and groove flooring planks.
To make the planks, HempWood blocks are sliced to create a 1/8 inch thick veneer that’s pressed onto a ½ inch plywood backing. The result is a very stable 5/8 inch thick engineered tongue and groove flooring in three color options: unfinished, natural and bourbon.
Flooring planks can be rift sawn, which has a vertical linear pattern resembling traditional lumber, or plain sawn, which has a more sporadic pattern. Plain sawn planks are harder than rift sawn.
The planks can be fastened to plywood or OSB subfloors with a standard nail gun. They can also be installed as a floating floor, but in that case, they have to be glued to one another at the edges.
Although this is an engineered veneer product, it needs to be treated like high-quality, solid, hardwood flooring. Vapor barriers are essential because HempWood is susceptible to moisture.
For instance, planks can be glued to a concrete slab, but if the slab isn’t poured over a vapor barrier, moisture drawn from the ground through the concrete can ruin them. And if the concrete hasn’t had time to fully cure, residual moisture can cause the adhesive to fail.
Even if it’s a bone-dry slab, adding a toxic adhesive to a non-toxic hemp floor defeats the purpose of investing in a healthy, sustainable product. If you plan on using adhesive, look into a zero-VOC type.
The Advantages
There are so many things to love about this product.
It’s fast-growing. Oak trees take 50-100 years to mature, while hemp can go from seed to lumber in just 150 days.
It’s extremely hard. The Janka hardness test measures wood’s resistance to denting and wear as measured in lbf or pound-force. Oak has a Janka hardness of 1300 lbf while hemp has a Janka hardness of 2000 lbf, almost as hard as Brazilian cherry wood. It’s also 25% harder than hickory, oak, or maple.
It’s eco-friendly. A hemp plot absorbs four times more carbon than a forest of the same size. By the time it’s harvested, a hectare of hemp will have taken in about 22 tons of carbon.
It’s fire-resistant. While hemp stalks are naturally flammable, HempWood is compressed to such a density that it earns a class B fire rating. That’s much more fire-resistant than softwood pine.
It’s non-toxic. Hemp planks are free of formaldehyde and VOCs. According to HempWood founder Greg Wilson, the wood flooring industry has conveniently stopped using the word “formaldehyde” in their marketing and switched to “phenolic resin” even though they are the same thing.
It’s also a lot healthier than those cheap, water-proof vinyl flooring products. Those products are made from a variety of chemicals and VOCs (volatile organic compounds) that can off-gas and cause headaches, nausea, nose and throat irritation. In large quantities, they can have more serious health effects like damage to our kidneys, liver or central nervous system.
Hemp boards’ extreme hardness has both pros and cons.
The Downsides
Every choice is a tradeoff, and hemp is no exception. Here are some relevant issues.
It’s not cheap. The people at HempWood use PureBond plywood to back their flooring, which costs 20% more than imported plywood. They also use a soy-based adhesive that costs $2.60 a pound, compared to phenolic formaldehyde which costs 17 cents a pound. Their unfinished flooring costs $8 per square foot while the finished versions are $10 per square foot.
It has to stay dry. This isn’t a good product for a bathroom because it’s susceptible to water and moisture. Room humidity must be kept in the 35%-55% range and you shouldn’t steam mop or wet mop the floor surface. You also can’t use wax, oil or soap, but must use hardwood floor cleaners instead. Stains must be oil-based because a water-based stain could cause swelling.
It’s hard. Yes, this is also a disadvantage. The manufacturer goes through two carbide-tipped saw blades a day because the material is so hard.
The Future
I was very inspired by this product and this company. It’s truly made in America, with all materials sourced from within a 100-mile radius of the factory. I also like that it’s not a Silicon Valley company that makes false claims—no one pretends that this is the Tesla Roadster of building materials, or that’s going to solve homelessness.
They also have a realistic, long-term vision. When I asked Greg Wilson what the future of HempWood is, he said that it’s a specialty product and that he doesn’t expect its market penetration to exceed a single-digit percentage. It’s also not intended for structural use.
The bottom line is that this is an eco-friendly, sustainably-sourced, American-made flooring and furniture alternative for commercial and residential applications. Off-site and on-site builders who serve a high-end market and/or have an environmental or health commitment might want to offer it to their customers, at least as an option.
