Summary: I frequently receive questions about termite wood damage and which lumber products are the best termite resistant woods. Here are the answers, but please don't ask me where all this wood can be purchased. That's a question for your lumber yard dealer.
The harder the wood, the tougher it stands up against termites. In fact, because termites prefer relatively soft woods like pine and fir, these woods are often used a termite lures. Raw pine stakes, driven into the ground, will soon be attached by termites, so pest control companies use these pine stakes to show homeowners that termites are active nearby.
Very dense wood is considered œhard wood. There is less soft wood in the grain of the wood. The hard wood may also have less pattern or swirls in the finish. Some people prefer a more uniform look, but that's all very subjective.
To determine the density of wood a method known as the Janka test is used. In case you're taking notes, the Janka Hardwood Scale was invented in 1906 by Gabriel Janka, an Austrian wood researcher. It's pretty simple. A steel ball measuring 0.444 in diameter is pushed into a piece of lumber until one-half of the ball has penetrated the wood surface. The pounds of force to push the ball into the wood is the number used to compare one piece of wood to another. A very low number would indicate soft wood, while a very high number would be registered for hard wood.
Douglas fir and Southern Yellow Pine woods are the softest, with Janka scores of 650 and 690 respectively. Well, actually, Balsa is the softest at 88, but who builds with Balsa wood? I've always thought teak was pretty strong wood, yet its JANKA score is only 1155, nearly double that of fir and pine, but still not very high on the list of all woods. I'll bet you thought Redwood Sequoias were as strong as they were tall, but they only score about 480, which means they are true softies.
I've had inquiries about Kempas wood, but it only registers a 1710 on the scale. So, if you really want dense wood you need to be working with wood from Brazil. The Brazilian Cherry, Rosewood, Teak and Walnut lumber all register above 2800, with the walnut going as high as 3680. Yet, the kings of hardness are the Verawood, Jutahy, Blackwood Solomon and Lignum Vitae, which is at the very top of the scale with a whopping 4500 Janka score.
I need to tell you some interesting things about Lignum Vitae, as long as we're on the topic. The wood is three times as hard as oak. Being so dense, it easily sinks in water, so I'm uncertain if this wood was every used to build the hulls of ships, but it was used for the propeller shaft. Even shaft bearings for the USS Nautilus, the world's first nuclear sub, were made of Lignum Vitae. The wood has its own natural lubricant and is virtually waterproof, unlike metal bearings. I also know this wood is used to make cricket balls, croquet mallets and it was a favorite with British police in the making of the truncheons or batons they carried.
The wood comes from a small, slow growing tree, which is now on the endangered list, even though most uses for this wood have been replaced by modern alloys and composite materials. The tree is native from Florida to Costa Rica and from Panama to the Bahamas.
|Wood Species||JANKA Hardness Number|
Brazilian Cherry (Jatoba)
North American Maple
Pine, Antique Heart
Walnut, American Black
Pine, Southern Yellow