Wood is classified as hard or soft. Generally, the harder the wood, like oak and maple, the heavier it will be. Softwoods are cheaper than hardwoods, but despite being light, they can be very strong and durable. For this reason, woodworkers use many light softwoods to make houses, furniture, cabinets and packing crates.
Although balsa wood is extremely light, it is actually a hardwood. Depending on the variety, it typically ranges from 2.72 to 6.35kg. per cubic foot and has a high strength to weight ratio. For this reason it is best known as the wood for model plane building. It absorbs shocks and vibrations well and is easy to cut and shape with hand tools. Balsa trees grow very quickly, reaching 60 to 90 feet with a 12- to 45-inch diameter in six to 10 years. Balsa is also in surfboards, flotation devices and insulation.
Bamboo is actually a grass, not a wood, but because of its properties, qualities and uses, people use it like wood in many parts of the world. Bamboo has a very high weight to strength ratio, higher than that of steel, but weighs only about 8.62kg. per cubic foot. For this reason, people have used bamboo in over 1,500 different ways, from bridges and houses to fences, tools and furniture. Bamboo can grow as fast as four feet per day.
Western red cedar is a softwood that weighs about 9.98kg. per cubic foot and grows throughout most of North America. It is fairly cheap, due to its large supply, is naturally resistant to rot, is free of resin and shrinks and swells less than other woods. Thus it is the wood of choice for outdoor furniture and fences. Cedar also repels moths, which makes it useful for making wooden storage cabinets.
Spruce is a softwood that weighs about 10.4kg. per cubic foot, with the highest strength to weight ratio of all woods, similar to that of steel. For this reason it is common in aeroplane, boat and house construction. Old growth spruce has excellent acoustic properties, which is why craftsmen have used it in guitar, piano and violin construction. Because it resists the elements well, people use it in outdoor construction and for masts on boats.