Most of us are fascinated by the beauty of finished hardwood floors, but have you ever wondered about the cumbersome process of making the planks? Hardwood flooring is made by placing hardwood floor planks with a uniform thickness and length together over a surface. To achieve this, the planks must be cut precisely. Understanding this process will help you recognize different grades of wood.
What Is Lumber?
Lumber is the generic term for various lengths of wood used for different construction purposes. They are cut lengthwise from the trunk and are characterized by rectangular or square cross sections. Each piece of lumber is surfaced and machined to produce specific cross sections. Lumber can be either patterned or worked. Patterned lumber usually has a tongue and groove cross section, decorative molding or shiplap siding.
Lumber is produced from both hardwood and softwood species. For hardwood flooring, species like oak, maple, walnut, birch and hickory are popular. You will also find softwoods like pine, hemlocks and firs. Lumber is graded according to size and defects in the raw materials. Defects like holes, knots, splits and missing pieces at the edges and corners can affect the wood’s beauty and quality. To better understand its qualities, lumber is graded accordingly.
The Manufacturing Processes
The following is the sequence of how hardwood lumber is made:
- Trees in a select area are inspected and marked as to whether they are ready to be cut down. If there is no roadway in the area, it has to be cut and graded using a bulldozer.
- Using gasoline-powered chainsaws, the trees are cut on either side to control the direction in which they fall.
- On a level terrain, the skidder is used to drag the fallen tree to a clearing to load it. In case the terrain is steep, a self-propelled yarder is used to move the logs.
- Trucks transport the logs to lumber mills where they will be processed further.
Debarking and bucking
- In this step, the lumber is loaded on a conveyer to bring it into the mill. Before doing so, the bark is removed with grinding wheels or a high-pressure water jet spray while the log is rotated on a long axis.
- While being carried by the conveyor belt, a huge circular saw cuts them into a predetermined length. This process is called bucking.
Sawing large logs is called head rig sawing; sawing smaller logs is called band sawing.
- Logs with a diameter of more than 2-3 ft are classified as large logs. They are clamped onto a moveable carriage that slides lengthwise on a set of rails. The entire process of head rig sawing is computerized, as the number of planks you can get from a log is calculated beforehand by the computer.
- Subsequent cuts are made by bringing the cart to the original position and moving the log sideways. Thinner lumber for making boards is cut from the outer layer of the logs while thicker lumber is cut from the centre of the log.
- Logs with a smaller diameter are put through a series of band saws and cut into 1-inch, 2-inch or 4-inch width planks.
Drying and seasoning
The cut lumber is moved to a place where it is dried and seasoned. This means the moisture level of the wood is minimized so it does not decay. The wood will shrink a bit when it dries completely. The lumber can also be air-dried or kiln-dried, depending on the moisture requirement based on where the wood is to be used. For the highest-quality flooring, wood must be completely dry.
Grade stamping and banding
Finally, the lumber is inspected through various tests that are mechanically administered and graded based on its defects. The grade, mill identification number and information like moisture content are stamped on each piece. They are bundled according to that information and transported to lumber yards.
Lumber Grades and Types
- Utility is the roughest grade of lumber. It is cheap and used for rough framing.
- Standard is rough but strong and used for general framing in construction.
- 3 common has loose knots where the surface is marred. It is used as utility and standard grade.
- 2 common has a smoother surface and tight knots. This lumber is good for making shelves.
- Select or select structural is a very high-quality grade which has further grade divisions into 1-3 and A-D. The lower grades of this type have comparatively more knots than higher grades.
- Clear lumber is noted for its uniform surface with no knots.
- Furring lumber is used for drywall or panelling, trim and edging, and can fit easily into smaller spaces.
- Finished lumber is useful for trimming and paneling. It is used primarily for furniture and decks but also flooring. This lumber is smooth, aesthetically appealing and available in a wide variety of sizes.
- Tongue and groove lumber are designed to fit together snugly, and is ideal for flooring and decorative treatments.
The process of manufacturing good lumber is time-consuming and results vary. The knowledge of different types of lumber, grades and relevant terms will help you shop for the best hardwood flooring at the right price.