Presentation on theme: "Wood. Terminology and Classification The terms wood, lumber, and timber are often used interchangeably, but each term has a distinct meaning. Wood Hard."— Presentation transcript:
Terminology and Classification The terms wood, lumber, and timber are often used interchangeably, but each term has a distinct meaning. Wood Hard fibrous substance lying beneath the bark of trees. Lumber Wood that has been sawn into construction members. Timber Lumber that is five inches or larger in its least dimension.
Terminology and Classification Wood is classified as softwood or hardwood depending on the type of tree it originates from. Softwoods, such as pine, fir, and spruce, come from needle-leaved conifers, which are evergreen Hardwoods, such as maple, oak, and sycamore, come from broad- leaved deciduous trees, which shed their leaves annually. The important difference between softwoods and hardwoods is botanical, which refers to the cellular structure of the two groups. Most hardwoods are in fact harder than softwoods; however balsa wood, one of the softest woods known is actually a hardwood.
Characteristics of Wood Wood consists of approximately 70% cellulose and 18% to 28% lignin, which is the adhesive imparting strength to the wood. The remainder is made up of minerals and extractives, which give wood its color, odor, and resistance to decay.
Cutting and Sawing Lumber Lumber can be cut from a log in two different ways: tangent to the annual rings, called plain-sawed in hardwoods and flat-grained or slain-grained in softwoods. Lumber cut radially to the annual rings is called quarter-sawed in hardwoods, and edge-grained or vertical-grained in softwoods. Lumber is classified as quarter-sawed if the grain is 45 degrees to 90 degrees to the wide face and plain-sawed if the grain is 0 degrees to 45 degrees to the wide face.
PLAIN SAWNED LUMBER AND TIMBER QUARTER SAWNED LUMBER AND TIMBER
Cutting and Sawing Lumber Characteristics of plain-sawed lumber include: 1.Distinct grain pattern, 2.May twist, cup, or wear unevenly, 3.Tends to have a raised grain, 4.Shrinks and swells more in width, less in thickness, 5.Less waste in cutting, and therefore less expensive.
Cutting and Sawing Lumber Characteristics of quarter-sawed lumber include: 1.Relatively even grain pattern, 2.Wears evenly with less warpage, 3.Shrinks and swells more in thickness, less in width, 4.More waste in cutting and therefore more costly.
Shrinkage, distortion, and warpage of lumber depends partially on the way lumber is cut from a tree. Wood shrinks most in the direction of the annual growth rings (tangentially); less across these rings (radially); and very little parallel to the grain (longitudinally).
As moisture content in the cells of wood changes, particularly as it dries out, wood members can change shape if the change moisture content is not done in controlled conditions. As wood dries out the amount of shrinkage differs in various directions. Shrinkage is limited to parallel to the grain of the wood. It is greatest when measured in a tangent to the growth rings. The amount of shrinkage along the radius of the wood is less than that tangentially. Depending on where in the log the member is cut from, uncontrolled drying can cause wood members to exhibit unusual shapes as shown here in this exaggerated illustration. Seasoning of Wood shrinkage stiffness strength
Making wood suitable for construction involved more than simply cutting down a tree and sawing the wood to size. Wood in a tree is green, that is, contains a large amount of water. If green lumber is used in construction, it will shrink as it dries out. Seasoning of Wood shrinkage stiffness strength appearance Making wood suitable for construction involved more than simply cutting down a tree and sawing the wood to size. Wood in a tree is green, that is, contains a large amount of water. If green lumber is used in construction, it will shrink as it dries out. To minimize shrinkage, lumber should be seasoned dried before use to between 10% to 20% moisture content. This can be accomplished by air drying, which takes several weeks or kiln drying.which takes only a few days. Over 90% of lumber is kiln dried Framing lumber is considered seasoned if its moisture content is 19% or less. An 18 2x10 loses approx 5 gallons of water Hardwood Inc.Tour Tuesday, Sept. 6, 2011
Drying Lumber Video 1:39 minutes
Wood Defects Variety of defects affect the strength appearance use and grading of lumber. Defects may be natural. damaged by insects decayed by fungus and of course, destroyed by fire. or caused by manufacturing
Wood Defects NATURAL DEFECTS: Knot: branch embedded in a tree and cut through manufacturing. Shake: pitted area sometimes found in cedar and cypress. Pitched Pocket: opening between growth rings and containing resin.
Wood Defects MANUFACTURED DEFECTS: Check: lengthwise grain separation caused by seasoning. Split: lengthwise separation of wood extending from one face to another. Wane: lack of wood on the edge or corner. Warp: shrinkage distortion of a plane surface, includes---bow, crook, cup and twist.
Pressure Treating Lumber Video 1:01 minutes Wood can be damaged by insects and decayed by fungus
Standardized terms and dimensions
Standardize Dimensions – Nominal Verse Actual size
Plywood Veneer Cutting forms parallel pattern forms repeating pattern forms random pattern
Sample Plain Sliced Patterns
Sample Quarter Cut Patterns
Miscellaneous Panels random matching slip matching book matching running match balance match center match
23 Every other veneer turned over Veneer joints match, creating symmetrical pattern Most common Used with plain slicing most Book Match
24 Leaves slipped off in sequence without turning Repeating grain - joints dont match Often used with quartered or rift veneers Slip Match
25 Veneer book broken Leaf sequence destroyed on purpose Appearance of boards Casual or Rustic More difficult than Book or Slip Random Match
T = Tension C= Compression Wood is generally stronger in compression than tension. Unlike other materials, the strength of wood is not the same in every direction for tension and compression. Wood is stronger when the load is applied parallel to the grain than perpendicular to the grain. In fact, the strength of wood in tension perpendicular to the grain is so low that this type of loading can easily cause the wood to split. For shear, wood is very strong perpendicular to the grain and relatively weak parallel to the grain. Therefore, horizontal shear stress (parallel to the grain) is often a design consideration, while vertical shear stress (perpendicular to the grain) is not.
What is Southern Pine? Video 1:00 minute Wood Species
Wood Species Guide uotes.cfm?do=guidehttp://www.hardwoodweb.com/lumber/rfq/q uotes.cfm?do=guide
Example of what we will see at tour: Purpleheart Lumber Sources Includes species in tropical regions of Central America and South America. Appearance Generally straight grained, sometimes interlocked, with a fine even texture. Creamy white sapwood and vibrant purple heartwood that turns to dark-purplish brown with exposure to light. Physical Properties Very heavy, hard, strong, and stiff with good decay resistance and stability in service. Steam-bends moderately well.
Structural Strength of Wood Species ( Fir, Hemlock, Pine, etc) Grade Direction of Grain ( parallel or perpendicular) Size and Shape Moisture Content
Definition of Moisture Content Weight of water compared to the weight of dry wood Formula for Moisture Content Weight of water as % of wt. of dry wood
What is considered an acceptable moisture content of framing lumber?
19% Weight of the water in the wood is 19% of the weight of the dry wood. If the wood was 100 pounds dry, then it has 19 pounds of water in it.
Particle Board manufactured from wood particles, such as wood chips, sawmill shavings, or even saw dust. Made with larger pieces of wood than used to make MDF
Oriented Strand Board (OSB) sometimes called waferboard
Oriented Strand Board (OSB)
O S B Video 1:08 minutes
Medium Density Fiberboard (MDF) Combination of softwood fibers, wax & resin. Stronger than particle board
Laminate Strand Lumber (LSL) Made up of strands of lumber instead of veneers
Laminated Veneer Lumber (LVL) LVL is made by gluing sheets of veneer together. Unlike plywood, here all veneer layers are going in the same direction. Wide panels are manufactured to the thickness of the desired lumber. The panels are ripped into lumber of nominal width.
Masonite Type of hardboard invented by William H. Mason. It is formed using the Mason method, using wooden chips and blasting them into long fibers with steam and then forming them into boards. The boards are then pressed and heated to form the finished boards. No glue or other material is added.
Plywood made from thin sheets of wood veneer, called plies or veneers, layered in opposite directions
49 What is hardwood plywood? Three or more layers of wood or wood products laminated into a single sheet FACES; Outside decorative veneers CORE; MDF, PB, VC, Combos
50 Construction balance Three is minimum Always Odd 3, 5, 7, 9…… Panel Balance a Must!
Plywood Video 2.21 minutes
Plywood is classified as interior or exterior depending on the type of adhesive used: moisture- resistant for interior use, and water-proof for exterior use. Plywood used in construction is primarily softwood. Plywood used for interior millwork or cabinetry is usually hardwood..
Plywood Plywood is classified as interior or exterior depending on the type of adhesive used: moisture-resistant for interior use, and water-proof for exterior use. Plywood used in construction is primarily softwood. Plywood used for interior millwork or cabinetry is usually hardwood. Plywood is graded according to quality of the veneer: A Best D poorest.
Span Rating First number - maximum recommended roof span in inches if used as roof sheathing Second number -maximum recommended span use as subflooring. For example, a panel identified as 32/16 can be used as roof sheathing over rafters spaced 32 inches on center or as subflooring over joists spaced 16 inches on center.
Glued Laminated Lumber (Glulam) These beams are made by gluing many boards together to form a structural member bigger than the trees from which the board were sawn. Since the load is carried by the material in the top and bottom faces and the middle only has to resist shear, high quality lumber is used in the top and bottom while medium grade lumber is used in the center. (gluelam or glulam) Joints between boards are typically scarf or finger joints.
Curves that remain in one plane are much easier to construct than compound curves (a dome). A dome is likely to be segmented curves. Glue Laminated Construction
Glulam Video 2:04 minutes
RPL Recycled Plastic Lumber Lumber-like products with a plastic content of 50% or more. Higher expansion & contraction with temperature changes. Less structural strength
I -Beams & I -Joists Veneer lumber is used for the flanges and plywood or OSB is used for the web to resist shear.