Kiln-Dried Woods
Wood can store moisture which may lead to a loss of durability. Many living room furniture pieces are made of kiln dried wood, which has been heated to eliminate the moisture. This prevents the wood from rotting and cracking under stressful conditions such as a kid bouncing up and down on the bed.
Hardwoods
A hardwood is the best type of wood to use on a bunk bed frame, including oak, maple and cherry. These woods are the most durable and capable of withstanding stress without cracking or feeling unstable. Hardwoods are heavier than most others and will usually cost more at both the lumber yard and your local furniture store. Bunk beds can be seen as a long term investment because most can be disassembled in the future and used as two free-standing frames.
Avoid Soft Woods
Pine and spruce are softer woods that may be used on lower-end bunk bed models. They won't hold up as long, especially under stressful conditions. Other cheaper woods to avoid include particle wood frames. These frames are the lowest on the sturdiness spectrum and are manufactured with tiny fragments of wood that are molded together. Particle wood cracks easily and will often continue to fall apart once that happens. They're are also hard to mend once the initial crack occurs.
Exterior Surfaces
Exterior surfaces such as the face of the bunk bed or other accents can contain softer woods without compromising overall strength and durability. Hardwoods should be used on the main parts of the frame that will be under the most pressure. Carved surfaces can often be constructed with veneer wood, which is softer than hardwood but allows for sculpting those detailed surfaces. Veneer wood may be softer, but it's of exceptional quality that won't split or warp over time.