Pine is the most common type of wood used for the manufacture of plywood products of all types. Construction-grade softwood plywood is almost all made of some type of pine. This is mostly because pine is an inexpensive wood to buy, due to its commonality and high growth rate. Of all the woodlands in the United States, there is more land covered by pine trees than any other type of tree.
The way pine grows makes for a high percentage of usage wood from the tree. Trunks of pine trees are almost always straight, without splitting into branches. Rather, branches grow out from the trunk at a right angle. This causes those branches to sag with time, giving the pine tree its distinctive triangular shape. It also means that the trunk runs pretty much the entire height of the tree, although it does get narrower as it gets higher.
The number and type of branches that a pine tree has means that the wood has a lot of knotholes in it. Pine wood without knotholes is more expensive, mostly due to its rarity. This is used for finish work, either turned into dimensional lumber or architectural moldings. Pine which has a lot of knotholes is normally used only for structural work, where it will be covered by other materials. But some people like the knotholes because they give a more rustic look to furniture and home construction.
This long, straight trunk is ideal for the manufacture of low-cost plywood, which starts out by putting logs on a huge lathe, so that large sheets of veneer can be peeled off the log. Quarter-sawn wood veneer, used in the manufacture of hardwood plywood, doesn’t give as much yield per log. Added to the fact that hardwood trees don’t have the long straight trunk of a pine, means that much less plywood veneer can be cut from a hardwood log for the manufacture of plywood.
The resulting plywood is lightweight, in comparison to plywood made from other woods. That makes it easier to work with. Finished projects are also easy to move around. Pine itself is less expensive than other varieties of wood, such as the many types of hardwoods, therefore pine plywood is also less expensive, often considerably less expensive.
Nevertheless, the light weight and soft texture of pine does have disadvantages. While fairly stiff and sturdy, it does have a tendency to wear down over time. Pine will scratch easier than some dense hardwoods, especially when we compare it to oak, maple or walnut. This means that when used in projects which receive rough use, pine will show wear faster and may wear out sooner.
Pine grain is smooth, with small pores which don’t absorb a lot. The color can vary considerably, ranging from a yellowish brown to a deep reddish brown, even though pine is often known for being a “white wood” and is often called by that name. It accepts paints well, which bond very well to the wood. However, it does not do as well with staining, as the wood does not absorb stain evenly, especially when comparing heartwood to sapwood. So stained finishes applied to pine may not come out evenly.
Types of Pine
While we think of pine as one single type of wood, and it is generally sold that way, pine plywood does not come from any one specific type of tree. Rather from a family of trees which all share the common name of “pine.” There are 126 species of pine within this family, although they don’t all exist in the same place and not all are used for manufacturing pine plywood. A few types of pine plywood are commonly enough known to have their own names:
- Knotty Pine – this is the type with many visible knots that gives off a rustic look. However, the knots are both small and tight, so they don’t weaken the wood.
- Heart Pine – has less knots, so it is not as great for a rustic look. However, it is both dense and strong, yet very soft and easy to work with. Heart pine literally comes from the heartwood, the oldest wood in the tree and is cut from the oldest pines harvested.
- Douglas Fir – This type of wood is tightly packed (knots and grains). Unlike other types of pine, it not only paints well, but stains well, giving an even appearance.
Uses for Pine Plywood
Softwood plywood is most commonly used for construction, although it is also used for industrial purposes at times. In construction, it is most often found used for wall and roof sheathing on homes, as well as for sub-flooring, although OSB is also allowable by building code for these applications, and is often used in place of softwood plywood, due to its lower costs.
This is not to say that pine plywood can only be used for construction uses. Higher grades of pine plywood are used for the manufacture of a wide variety of projects, especially by do-it-yourselfers and woodworking hobbyists. AC grade pine plywood provides the hobbyist with a plywood product that has a good surface finish, which does not have a high price. People make a considerable amount of furniture out of pine plywood, especially when they want an antique or rustic look. Bookcases, wardrobes, bed frames, chairs, and tables are all made out of this plywood product.
Pine plywood, specifically marine grade pine plywood, is used to make boats. This is an excellent choice, because of its light weight and high strength to weight ratio. Marine grade pine plywood is manufactured without any voids, as those can cause more rapid delaminating when exposed to a high moisture environment.
Lower grades of pine plywood, such as BC grade plywood, are often used for making rough-use furniture, such as shelving and workbenches for the workshop. This provides high strength at a lower cost. Since finish isn’t so important in these applications, it makes sense to use the BC grade plywood, rather than the more expensive AB or AC grade.
Cautions with Pine Plywood
Like any other plywood product, pine plywood is susceptible to water damage, especially when water is soaked up through the end grain. This can be limited by sealing the edges of cut pieces, an excellent idea if the project is going to be regularly exposed to water. If your project doesn’t cover the edges or seal them, you can seal the edges of plywood with painter’s caulking. Just run a bead down the edges of the board, and then wipe it into the grain with your finger, adding more caulking when needed. This can easily be painted over.
Keep in mind that furniture and other projects made with pine are not as durable as those made with harder, denser woods. While convenient, easy to work with and lower cost, projects may not last as long, especially if they are exposed to a lot of wear.
You can increase the durability of these projects by edging the pine plywood with hardwood pieces. While those will still wear, they won’t wear as heavily as the pine plywood will. It is also important to periodically refinish plywood which receives a lot of wear, as the finish provides protection for the wood, especially against moisture. Should the finish wear off and not be replaced, the underlying wood will be more likely to become water damaged.