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34 Cards in this Set
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1. What is the function of the Medula ring?
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Functions of the Pith or Medulla
The cells of the pith store water and starch. They allow for the exchange of gases through the intercellular air spaces. The medullary rays transport substances from the xylem and phloem to the inner and outer parts of the stem. |
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What is Heartwood/Sapwood?
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As one layer of wood succeeds another, the cells in the inner layer dies (cease to function as food storage) and become useful only to give stiffness to the tree. This older wood, known as heartwood is usually darker in color, drier and harder than the living layer (sapwood).
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Characteristics of Heartwood vs. sapwood.
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1. Equal strength
2. Heartwood is more durable than sapwood. 3. Sapwood takes preservative treatment more readily than heartwood and it is equally durable when treated. |
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*summerwood
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In many trees, each annual ring is divided into 2 layers. The inner layer consists of cells with relatively large cavities. This heavier, harder, stronger material is called the summerwood. The amt of summerwood is one measure of the density of the wood; the higher the density the greater the strength.
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*springwood
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is the portion of the annual growth ring formed during the early part of the yearly growth period. It is lighter in color, less dense, and not as strong as summerwood.
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flat-grained vs. plain-sawed
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Most trees are sawed so that the growth rings form an angle of less than 45 degrees with the surface of the boards produced. Such lumber is called flat-grained in softwoods and plain-sawed in hardwoods (figure 2 - insert). This is the least expensive method, but more likely to shrink or warp.
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edge-grained or vertical-grained in softwoods and quarter-sawed in hardwoods.
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There is another method in which the wood is cut with the growth rings at an angle greater than 45 degrees. Lumber cut by this method is known as edge-grained or vertical-grained in softwoods and quarter-sawed in hardwoods. The lumber it produces is usually more durable and less likely to warp or shrink. Quarter-sawed lumber is often used for hardwood floors. In order to obtain the most lumber from the log, most logs are cut using a combination of the two methods.
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Lumber falls into one of two general classifications: hardwood or softwood.
Hardwoods come from _________ trees such as ____________. Softwoods come from ____________ trees such as ___ and ______. |
Hardwoods come from deciduous (leaf-bearing) trees such as oak and maple.
Softwoods come from coniferous (cone-bearing) trees such as pine and fir. The term softwood does not mean it is not strong or durable. |
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Example Hardwoods
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Alder (red alder and fruitwood)
Ash - used for furniture, etc. Basswood - soft hardwood - veneer Beech - strong, furniture Birch - strong Cherry - cabinets, furniture Chestnut - cabinets, paneling Elm - heavy construction purposes Gum - tends to warp, furniture Larch - strong, fairly hard, construction Mahogany -furniture, trim, paneling Sugar maple - furniture, flooring Silver maple - not very strong White Oak - flooring, furniture Red oak - furn, cabinets Poplar - inexp. furn, crates, plywood Walnut - cabinets, furn., flooring |
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Example Softwoods
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Western red cedar - lacks strength, shingles shakes, siding, lumber
Tennessee cedar - strong odor that acts as an insect repellent, trunk linings and closets Cypress - durable, interior trim, cabinet work Douglas Fir - strong & durable, plywood Western hemlock - works easily - general construction. White pine - furniture and millwork Sugar pine - inexp. furn & interior millwork Ponderosa pine - strong - door & window frames Lodgepole pine - timbers for miners Southern yellow pine - hard - floor planks, beams, timbers Redwood - lacks strenth - planking for decks & shingles White spruce - pulp wood & lt. const. Engelmann spruce - oars, paddless, muscial instr. Sitka spruce - strong - masts, scaffolding, general construction. |
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Types of defects in lumber
1. Naturally occuring 2. Manufacturing defects Name a few Naturally occuring defects found in lumber: |
1. Naturally-Occurring Defects
- Burl - localized severe distortion of the grain. 2. Compression wood - used by artists for wood carving 3. Decay - disintegration of the wood substance due to fungi. dote, rot and unsound wood 4. Holes 5. Knots 6. Pitch 7. Pitch streak 8. Pocket 9. Stained wood |
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Types of defects in lumber:
1. Naturally occuring 2. Manufacturing Defects Name several Manufacturing defects |
1. Chipped grain
2. Torn grain 3. Raised grain 4. Loosened grain 5. Skips 6. Hit or miss 7. Mismatch 8. Machine burn 9. Machine bite 10. Machine gourge 11. Machine offset 12. Chip marks 13. Knife marks 14. Wary dressing 15. Wane |
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A simple way to check for too much moisture in the lumber is
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to hit the lumber with a hammer. If moisture comes to the surface in the dent left by the hammer, the lumber is too wet and should not be used.
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Moisture and Warping - various kinds of damage that can occur when drying lumber. Most can be prevented if lumber is dried and stored properly
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1. Wane
- twist - bow - crook - cup - split - check - shake |
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Wanes
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Wanes occur when lumber is cut too close to the outer surface of the tree
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The terms check, split, and shake are used to define
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separations at the end of a length of lumber.
A aplit, is a crack that extends all the way through the wood. A check is a crack along the growth rings. A shake is a hollow between the growth rings. |
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The following are various types of lumber defects during the drying of lumber. Most are preventable if lumber is properly dried and stored.
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1. large surface check with knot and pocket
2. pitch streak 3. shake 4. split 5. cup 6. bow 7. torn grain-heavy 8. machine offset 9. wane and dip |
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Drying Lumber - 2 methods
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1. Kiln drying - most common - few days.
2. air drying - stacked outdoors and allowed to dry for up to 3 months. Still likely to have higher moisture content than kiln-dried lumber. |
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Stacking interior finish materials on top of scrap lumber serves 2 purposes:
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1. It prevents moisture in concrete floor from coming in contact with bottom piece.
2. Although finish material is covered, possibility of pipe bursting and water flowing on floor. |
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Calculating dressed softwood lumber sizes
General rule: |
Boards with nominal width of 1" or less have dressed dimesnions that are 1/4" smaller
Boards with nominal width of 2" to 6" have dressed dimensions that are 1/2" smaller Boards with widths greather than 6" - subtrract 3/4" from nominal dimensions to get dressed sizes. General rule - always perform an actual measurement. |
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Nominal and dressed (actual) sized of dimension lumber (in inches)
Nominal 2 x 2 2 x 4 2 x 6 2 x 8 2 x 10 2 x 12 |
Nominal Dressed
2 x 2 1-1/2 x 1-1/2 2 x 4 1-1/2 x 3-1/2 2 x 6 1-1/2 x 5-1/2 2 x 8 1-1/2 x 7-1/4 2 x 10 1-1/2 x 9-1/4 2 x 12 1-1/2 x 11-1/4 |
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Matched lumber is
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end-dressed to create a smooth joint with another piece of lumber.
Tongue-and-groove joint Patterned lumber - 2 pieces of lumber are tapered opposite to form a smooth overlapping joint - called a shiplap. |
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The average or standard size of plywood is
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4'-0" x 8'-0". This is standard in the construction field.
Sheathing-grade plywood is nominally sized by manufacturer to allow for expansion, 4 x 8 is really 47 3/4" x 95 3/4". Thickness of plywood varies from 3/16" to 1-1/4". Common sizes are 1/4",1/2", and 5/" for finish paneling |
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Large quantities of lumber are normally ordered by the board food.
A board foot is equivalent to a piece of lumber that is 1" THICK, 12" WIDE, AND 1' LONG. When calculating board feet, always make sure you use the nominal lumber dimensions. The formula used to calculate board feet: |
Board feet = # pieces x thickness (in inches) x width (in inches) x length in feet / 12.
Example: 20 pieces of 2 x 6 lumber that are each 8' long equals ? board feet. 20 x 2 x 6 x 8 / 12 = 1920/12 = 160 board feet. |
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Calculate board feet:
20 pieces of 2 x 6 lumber that are each 8' long equals ______ board feet. |
Board feet = # pieces x thickness (in inches) x width (in inches) x length in feet / 12.
Example: 20 pieces of 2 x 6 lumber that are each 8' long equals ? board feet. 20 x 2 x 6 x 8 / 12 = 1920/12 = 160 board feet. |
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To caluclate the amount of sheet materials such as plywood, particleboard, drywall, and sheathing you need, calculate area to be covered (length x width = area). Area will always be the square of the values used (square feet, square inches, etc.). To figure amt of plywood decking needed for a 20' by 41' roof:
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20 x 41 = 820 square feet.
A standard 4' by 8' sheet contains 32 squre feet. Therefore, if you divide 820 by 32, it yields 25-5/8 sheets, which is then rounded to 26 sheets. Trim and moldings are priced by the lineal foot and are ordered by the dimesnion of the piece (for example, 150' of 1" quarter round molding). |
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Pressure treated lumber
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is softwood lumber protected by chemical preservatives forced deep into the wood through a vacuum-pressure process.,
Used for landscape timbers, sill plates, and foundations. Builidng of decks, porches, docks and other outdoor structures subject to decay from exposure to the elements. Low priced in comparison with redwood & cedar. Comes in 3 grades - designated by pounds per cubic foot of preservative retention. Above ground, ground contact grade, below ground. |
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Glue laminated lumber (glulam)
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Glulam is made from lengths of solid, kiln-dried lumber that have been glued together. Popular in architectural applications where exposed beams are used. Can be used in areas subject to high winds or earthquakes. Glulam is available in 3 appearance greades: industrial, architectural, and premium. Available in widths from 2-1/2 to 8-3/4 and depths from 5-1/20 to 28-1/2. Available in very long lengths.
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Laminated veneer lumber (LVL).
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Douglas fir and southern pine are primary sources. thin 1/20" to 3/16" sheets are peeled from tree in widths of 27" or 54". The veneers are laid-up in a staggered pattern with veneers overlapping to increase strenth. The grain of each layer runs in the same direction as the other layers. The veneers are bonded with an exterior-grade adhesive, then pressed together and heated under pressure. LVL is used for floor and roof beams and for ehaders over windows and doors.
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veneered wood
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Plywood is made of layers (plies) of wood veneers. A layer may be 1/16" to 5/8" thick. Center is core. As layers are added on either side, they are placed at right nagles, increasing strength.
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The plywood used in the manufacture of cabinets, doors, furniture and finished components in known as hardwood plywood. This type of plywood may have any of 4 different types of core:
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1. a lumber core
2. a particleboard core 3. a veneer core (construction plywood) 4. a fiberboard core The plywood manufactured for industrial use is often called soft plywood and has a veneer core. |
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OSB
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Oriented Strand Board is a manufactured structural panel used for wall and roof sheathing and single-layer floor construction. OSB consists of compressed wood strands arranged in 5 or more cross banded layers and bonded with phenolic resin.
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Qualities of OSB:
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1. dimensional stability
2. stiffness 3. fastener holding capacity 4. no core voids |
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Uses of Engineered Wood Products
PSL LVL Wood I-beams LSL |
PSL - Parallel Strand Lumber used for columns, ridge beams, girders, and headers.
LVL - Laminated Strand Lumber used for form headers and beams Wood I-beams are used to frame roofs as well as floors. Also used LSL studs, top plates, and soleplates in place of lumber to frame walls. |
