WOOD CHAPTER 3 Monday, April 9, 12
WOODCHAPTER 3
Monday, April 9, 12
TREE ANATOMY
OUTER PROTECTION OF DEAD
BARK
INNER LIVING BARK (COMPOSED OF HOLLOW LONGITUDINAL CELLS THAT CONDUCT NUTRIENTS FROM THE LEAVES TO THE ROOTS)
CAMBIUM LAYER - RESPONSIBLE FOR CREATING NEW CELLS
Monday, April 9, 12
TREE ANATOMY
THICK LAYER OF LIVING WOOD CELLS INSIDE THE CAMBIUM IS
CALLED THE SAPWOOD (THIS IS WHERE NUTRIENTS ARE STORED)
AT THE INNER EDGE OF THIS RING, THE SAPWOOD DIES AND
BECOMES HEARTWOOD (MANY TIMES IT IS A DARKER COLOR)
Monday, April 9, 12
TREE ANATOMY
AT THE VERY CENTER OF THE
TREE IS THE PITH, A WEAK ZONE OF WOOD CELLS THAT WERE THE FIRST YEAR’S GROWTH
Monday, April 9, 12
TREE ANATOMY
WOOD IS MADE OF TUBULAR CELLS WHOSE LONG AXIS IS PARALLEL TO THE LONG AXIS OF THE TRUNK
CELLS ARE STRUCTURED OF TOUGH CELLULOSE
CELLS ARE BOUND TOGETHER WITH LIGNIN
THE DIRECTION OF THE LONG AXIS OF THE CELLS IS REFERRED TO AS THE
GRAIN OF THE WOOD
Monday, April 9, 12
TREE GROWTH
THE CAMBIUM MANUFACTURES NEW SAPWOOD CELLS IN THE SPRING
GROWTH OCCURS RAPIDLY DUE TO COLD TEMPERATURES AND AMPLE GROUND WATER
THESE CELLS ARE “SPRINGWOOD” OR “EARLYWOOD” CELLS
Monday, April 9, 12
TREE GROWTH
GROWTH IS SLOWER IN THE SUMMER BECAUSE OF HIGH HEAT AND LOWER WATER
CELLS ARE MORE DENSE THAN SPRINGWOOD CELLS
THESE CELLS ARE “SUMMERWOOD” OR “LATEWOOD” CELLS
THESE STAGES RESULT IN THE RINGS WE COUNT ON TREE TRUNKS
Monday, April 9, 12
SOFTWOODS & HARDWOODS
SOFTWOOD COMES FROM CONIFEROUS TREES
HARDWOOD COMES FROM BROAD LEAF TREES
NAMES ARE DECEPTIVE BECAUSE SOFTWOOD CAN ACTUALLY BE MORE DENSE (HARDER) THAN HARDWOOD
Monday, April 9, 12
SOFTWOODS & HARDWOODS
SOFTWOOD TREES HAVE A SIMPLE MICROSTRUCTURE CONSISTING OF MAINLY LONGITUDINAL CELLS WITH ONLY A SMALL PERCENTAGE OF RADIAL CELLS
Monday, April 9, 12
SOFTWOODS & HARDWOODS
HARDWOOD TREES ARE MORE COMPLEX IN STRUCTURE, WITH A LARGER PERCENTAGE OF RAYS AND TWO DIFFERENT TYPES OF LONGITUDINAL CELLS:
FIBERS (SMALL DIAMETER)
VESSELS (LARGE DIAMETER)
Monday, April 9, 12
SOFTWOODS
SOFTWOOD LUMBER HAS AN UNINTERESTING GRAIN STRUCTURE
MOST LUMBER FOR BUILDING FRAMING COMES FROM SOFTWOODS
THEY ARE LESS EXPENSIVE AND MORE PLENTIFUL
Monday, April 9, 12
HARDWOODS
HARDWOOD LUMBER HAS BEAUTIFUL GRAIN STRUCTURE
USED FOR FINE FURNITURE AND INTERIOR FINISH DETAILS
THEY ARE MORE EXPENSIVE AND LESS PLENTIFUL
Monday, April 9, 12
CERTIFIED WOOD
CERTIFIED WOOD COMES FROM FORESTS THAT ARE MANAGED FOR THEIR LONG-TERM ECOLOGICAL SUSTAINABILITY AND ECONOMIC VIABILITY
FOREST STEWARDSHIP COUNCIL (FSC) IS PRIMARY CERTIFIER
Monday, April 9, 12
LUMBER
1. BEGINS WITH THE FELLING OF TREES AND THE TRANSPORTATION OF LOGS TO THE SAWMILL
2. EACH LOG IS STRIPPED OF BARK
3. PASSED THROUGH A HEADSAW (CAN BE CIRCULAR OR BAND SAW) TO REDUCE THE LOG INTO UNTRIMMED SLABS OF LUMBER
Monday, April 9, 12
LUMBER
4. THE SAWYER (WITH COMPUTER HELP) JUDGES HOW TO OBTAIN THE MAXIMUM MARKETABLE WOOD FROM EACH LOG
5. USING HYDRAULIC MACHINERY TO ROTATE AND ADVANCE THE LOG, THE SAWYER CUTS THE LOG USING A SUCCESSION OF CUTS
Monday, April 9, 12
LUMBER
6. A CONVEYOR BELT CARIES THE SAWED OFF PIECES AWAY TO SMALLER SAWS WHERE THEY ARE REDUCED TO SQUARE EDGE PIECES OF DESIRED WIDTHS
Monday, April 9, 12
LUMBER
Monday, April 9, 12
PLAINSAWING
THE SEQUENCE AND PATTERN WITH WHICH THE LOG IS SAWN AFFECT THE ORIENTATION OF THE GRAIN WITHIN THE FINISHED PIECES
PLAINSAWN LUMBER USES A METHOD THAT PRODUCES THE MAXIMUM YIELD OF USEFUL PIECES (THEREFORE GREATEST ECONOMY)
TYPICAL FOR STRUCTURAL LUMBER
Monday, April 9, 12
PLAINSAWING
THE ORIENTATION OF THE GROWTH RINGS VARIES ALONG THE BOARD’S WIDTH
A LARGE PORTION OF THE BOARD’S WIDER FACE HAS A GRAIN PATTERN IN WHICH THE ANNUAL RINGS ARE ORIENTED CLOSE TO PARALLEL WITH THE FACE
THIS LUMBER IS CALLED “FLAT-GRAIN”
Monday, April 9, 12
PLAINSAWING
“FLAT-GRAIN” LUMBER HAS A TENDENCY TO WARP OR DISTORT DURING SEASONING
Monday, April 9, 12
QUARTERSAWING
QUARTERSAWN LUMBER USES A METHOD THAT PRODUCE EDGE-GRAIN OR VERTICAL GRAIN LUMBER
TYPICAL FOR STRUCTURAL LUMBER
ANNUAL GROWTH RINGS RUN MORE CONSISTENTLY PERPENDICULAR TO THE PIECES’ WIDER FACES
Monday, April 9, 12
QUARTERSAWING
VERTICAL GRAIN BOARDS TEND TO REMAIN FLAT DESPITE CHANGES IN MOISTURE CONTENT
QUARTERSAWING IS MORE EXPENSIVE BECAUSE MORE OF THE LOG IS WASTED AND IS USUALLY RESERVED FOR FINISH BOARDS (OFTEN HARDWOODS)
Monday, April 9, 12
SAWING OF A LARGE LOG
Monday, April 9, 12
SEASONING
GROWING WOOD CONTAINS WATER
THIS CAN RANGE FROM 30% TO 300% OF THE OVEN DRY WEIGHT OF THE WOOD
AFTER A TREE IS CUT, WATER STARTS TO EVAPORATE
“FREE WATER” IS THE FIRST TO EVAPORATE (THE WATER IN THE VOIDS OF THE CELLS)
Monday, April 9, 12
SEASONING
WHEN THE FREE WATER IS GONE, THE TREE STILL CONTAINS 26-32% MOISTURE
THIS “BOUND WATER” IS HELD WITHIN THE CELL WALLS
AS THE BOUND WATER EVAPORATES, THE WOOD STARTS TO SHRINK
SHRINKAGE, STIFFNESS AND STRENGTH INCREASE STEADILY AS MOISTURE DECREASES
Monday, April 9, 12
SEASONING
WOOD CAN BE DRIED TO ANY DESIRED MOISTURE CONTENT
FRAMING LUMBER IS CONSIDERED SEASONED WHEN IT HAS A MOISTURE CONTENT OF 19%
FOR FINER CONTROL, LUMBER WITH A MOISTURE CONTENT OF 15% (MC-15) IS ALSO PRODUCED
Monday, April 9, 12
SEASONING
WOOD WILL MAINTAIN AN EQUILIBRIUM WITH THE SURROUNDING AIR MOISTURE
IT IS THEREFORE OF LITTLE USE TO HAVE FRAMING LUMBER WITH A MOISTURE CONTENT BELOW 13%
FINISH CARPENTRY & ARCHITECTURAL WOODWORK USE WOOD THAT RANGES FROM 5-11%
Monday, April 9, 12
SEASONING
MOST LUMBER IS SEASONED AT THE SAWMILL
CAN BE AIR DRIED IN LOOSE STACKS FOR A PERIOD OF MONTHS
OR KILN DRIED (MORE COMMON) FOR A SHORT TIME IN CAREFULLY CONTROLLED CONDITIONS
Monday, April 9, 12
SHRINKAGE
WOOD DOES NOT SHRINK AND SWELL UNIFORMLY WITH CHANGES IN MOISTURE
SHRINKAGE ALONG THE LENGTH OF THE LOG
(LONGITUDINAL SHRINKAGE) IS NEGLIGIBLE
Monday, April 9, 12
SHRINKAGE
SHRINKAGE IN THE RADIAL DIRECTION (RADIAL SHRINKAGE) IS VERY LARGE
Monday, April 9, 12
SHRINKAGE
SHRINKAGE AROUND THE CIRCUMFERENCE OF THE LOG
(TANGENTIAL SHRINKAGE) IS ABOUT TWICE RADIAL SHRINKAGE (THE LARGEST TYPE OF SHRINKAGE)
Monday, April 9, 12
SHRINKAGE
IF A LOG IS SEASONED WHOLE, IT WILL NOT SHRINK MUCH ALONG THE LENGTH (LONGITUDINAL), BUT WILL SHRINK IN DIAMETER (RADIAL) AND TANGENTIALLY CAUSING THE LOG TO CHECK
Monday, April 9, 12
SHRINKAGE
DISTORTION OF A BOARD SAWN FROM A LOG VARIES BASED ON WHERE THE BOARD COMES FROM WITHIN THE LOG
Monday, April 9, 12
SURFACING
LUMBER IS SURFACED TO MAKE IT SMOOTH AND MORE DIMENSIONALLY PRECISE
ROUGH (UNSURFACED) LUMBER IS ALSO AVAILABLE
MOST LUMBER IS SURFACED ON 4 SIDES (S4S)
HARDWOODS CAN BE S2S
Monday, April 9, 12
LUMBER DEFECTS
DEFECTS CAN COME FROM:
GROWTH CHARACTERISTICS (DEFECTS CAUSED BY THE GROWTH OF THE TREE)
MANUFACTURING CHARACTERISTICS (DEFECTS CAUSED DURING MANUFACTURE)
Monday, April 9, 12
LUMBER DEFECTS
TYPES OF “GROWTH CHARACTERISTICS” DEFECTS
KNOTHOLES
DECAY
INSECT DAMAGE
Monday, April 9, 12
LUMBER DEFECTS
TYPES OF “MANUFACTURING CHARACTERISTICS” DEFECTS:
CHANGES RESULTING FROM DIFFERING RATES OF SHRINKAGE
SPLITS & CHECKS (CAUSED BY SHRINKAGE STRESSES)
Monday, April 9, 12
TYPES OF NON-UNIFORM SHRINKAGE
Monday, April 9, 12
LUMBER GRADING
GRADES OCCUR FOR APPEARANCE OR FOR STRUCTURAL STRENGTH/APPEARANCE (DEPENDING ON INTENDED USE)
LUMBER IS SOLD BY SPECIES & GRADE
Monday, April 9, 12
LUMBER GRADING
MAIN BEAMS OR STRUCTURAL MEMBERS ARE OFTEN A HIGH GRADE/HIGH COST
REMAINING MEMBERS ARE OFTEN INTERMEDIATE GRADE/LOWER COST
FOR BLOCKING, THE LOWEST GRADE IS ADEQUATE
Monday, April 9, 12
LUMBER GRADING
STRUCTURAL GRADING CAN BE DONE BY MACHINE OR BY PERSON
VISUAL GRADING (BY PERSON) ALLOWS A PERSON TO JUDGE QUALITY AND STAMP IT WITH A GRADE IN ACCORDANCE WITH INDUSTRY WIDE GRADING RULES
Monday, April 9, 12
LUMBER GRADING
IN MACHINE GRADING, AN AUTOMATIC DEVICE ASSESSES THE STRUCTURAL PROPERTIES OF THE WOOD AND STAMPS A GRADE AUTOMATICALLY ON THE PIECE.
APPEARANCE GRADING IS DONE VISUALLY
Monday, April 9, 12
LUMBER GRADING
FOR A TYPICAL HOUSE, LIGHT FRAMING LUMBER IS USUALLY ORDERED “#2 AND BETTER” WHICH IS A MIXTURE OF #1 & #2 LUMBER
Monday, April 9, 12
DIMENSION LUMBER GRADES
Monday, April 9, 12
STRUCTURAL PROPERTIES OF WOOD
WOOD IS USUALLY:
STRONGER IN COMPRESSION THAN IN TENSION
STRONGER PARALLEL TO THE GRAIN THAN PERPENDICULAR TO THE GRAIN
STRENGTH VARIES BY TYPE AND GRADING
Monday, April 9, 12
LUMBER DIMENSIONS
LUMBER SIZES ARE GIVEN IN
NOMINAL DIMENSIONS SUCH AS 2 X 4 (TWO BY FOUR)
TRUE SIZES ARE LESS THAN THESE NOMINAL DIMENSIONS
A 2 X 10, FOR EXAMPLE IS 1.5 BY 9.25 INCHES BY THE TIME IT IS FOR SALE
NOMINAL DIMENSIONS ARE WRITTEN WITHOUT INCH MARKS!!
Monday, April 9, 12
LUMBER TERMINOLOGY
PIECES OF LUMBER THAT ARE LESS THAN 2 INCHES IN
NOMINAL THICKNESS ARE CALLED BOARDS
PIECES FROM 2 TO 4 INCHES IN THICKNESS ARE
REFERRED TO AS DIMENSION LUMBER
PIECES NOMINALLY 5 INCHES AND MORE IN THICKNESS
ARE REFERRED TO AS TIMBERS
Monday, April 9, 12
LUMBER TERMINOLOGY
LUMBER IS COMMONLY SUPPLIED IN 2’ INCREMENTS, 8’, 10’, 12’, 14’, 16’
RAFTER MATERIALS ARE OFTEN STOCKED IN SIZES UP TO 24’
LUMBER IS PRICED BY THE BOARD FOOT - A MEASUREMENT BASED ON NOMINAL DIMENSIONS
Monday, April 9, 12
BOARD FOOT
A BOARD FOOT OF LUMBER IS DEFINED AS A SOLID VOLUME OF 12 SQUARE INCHES IN NOMINAL CROSS SECTIONAL AREA AND ONE FOOT LONG
A 1X12 OR 2X6 THAT IS 10 FEET LONG EACH CONTAINS 10 BOARD FEET
Monday, April 9, 12
WOOD PRODUCTS
MUCH OF THE WOOD USED IN CONSTRUCTION TODAY IS PROCESSED INTO MANUFACTURED PRODUCTS
DESIGNED TO:
OVERCOME SHORTCOMINGS OF REGULAR WOOD
MAXIMUM UTILIZATION OF WOOD FIBER FROM EACH TREE
Monday, April 9, 12
GLUE-LAMINATED LUMBER
JOINING TOGETHER SMALLER STRIPS OF WOOD TO FORM A LARGER STRUCTURAL MEMBER
JOINING OCCURS WITH GLUE
LAMINATE BECAUSE:
SIZE
SHAPE
QUALITY
Monday, April 9, 12
GLUE-LAMINATED LUMBER
Monday, April 9, 12
GLUE-LAMINATED LUMBER
VIRTUALLY ANY SIZE STRUCTURAL MEMBER CAN BE MADE BY LAMINATING (UP TO MACHINERY LIMITS)
CAN BE LAMINATED INTO SHAPES LIKE CURVES, ANGLES AND VARYING CROSS SECTIONS
DEFECTS CAN BE CUT OUT BEFORE LAMINATION (RESULTING IN HIGHER QUALITY)
Monday, April 9, 12
GLUE-LAMINATED LUMBER
INDIVIDUAL LAMINATIONS ARE COMMONLY 1.5 INCHES THICK (EXCEPT IN SMALL RADIUS CURVES WHICH ARE 0.75 INCHES THICK)
END JOINTS ARE EITHER FINGER JOINTED OR SCARF JOINTED
SIZES RANGE FROM 9 TO 75 INCHES IN DEPTH DEPENDING ON SPAN AND LOCATION
Monday, April 9, 12
HYBRID GLULAM BEAMS
SUBSTITUTE COMPOSITE LAMINATED VENEER LUMBER (LVL) FOR USUAL SOLID WOOD TOP AND BOTTOM
WITH STRONGER MEMBERS WHERE MOST STRUCTURAL STRESS OCCURS, BEAMS CAN BE 20% STRONGER AND 15% STIFFER OVERALL
Monday, April 9, 12
ENGINEERED LUMBER (STRUCTURAL COMPOSITE)
PRODUCTS MADE FROM WOOD VENEERS OR WOOD FIBER STRANDS AND GLUE
Monday, April 9, 12
LAMINATED STRAND LUMBER (LSL)ORIENTED STRAND LUMBER (OSL)
MADE FROM SHREDDED WOOD STRANDS THAT ARE COATED WITH ADHESIVE THEN PRESSED INTO A RECTANGULAR CROSS SECTION AND CURED UNDER HEAT AND PRESSURE
LSL STRANDS ARE LONGER THAN OSL STRANDS
LEAST EXPENSIVE OF COMPOSITE PRODUCTS
MOSTLY FOR RIM BOARDS AND SHORT SPAN HEADERS
Monday, April 9, 12
LAMINATED VENEER LUMBER (LVL)
MADE FROM THIN WOOD VENEER SHEETS (AS WIDE AS THE MEMBER IS DEEP) THAT ARE GLUED AND LAMINATED INTO THICKER MEMBERS
LVLS ARE SIMILAR TO PLYWOOD IN LOOK, BUT WITHOUT THE CROSSBANDS
OFTEN USED FOR LONGER SPAN HEADERS AND FLOOR BEAMS
Monday, April 9, 12
PARALLEL STRAND LUMBER (PSL)
MADE FROM LONG THIN STRIPS OF WOOD VENEER THAT ARE GLUED AND PRESSED IN A PROCESS SIMILAR TO THAT FOR LSL AND OSL BUT WITH THE UNIFORM STRIPS ARRANGED IN A MORE UNIFORMLY PARALLEL MANNER
HEAVIEST, STRONGEST AND MOST EXPENSIVE
OFTEN USED FOR LONGER SPAN HEADERS AND FLOOR BEAMS
Monday, April 9, 12
I-JOISTS
FLANGES OF MEMBERS MAY BE SOLID WOOD, LVL OR LSL
WEBS ARE TYPICALLY OSB OR PLYWOOD
USE WOOD MORE EFFICIENTLY THAN TRADITIONAL LUMBER & CAN SPAN FARTHER BETWEEN SUPPORTS
MORE DIMENSIONALLY STABLE
Monday, April 9, 12
STRUCTURAL FINGER-JOINTED LUMBER
SHORT LENGTHS OF SOLID LUMBER SCRAP ARE FINGER-JOINTED END-TO-END INTO LONGER LENGTHS
OFTEN USED FOR STUDS AND POSTS
FOR FRAMING TALL WALLS WITH LARGE OPENINGS
Monday, April 9, 12
WHAT ARE SOME ADVANTAGES AND DISADVANTAGES OF ENGINEERED LUMBER?
Monday, April 9, 12
ADVANTAGES/DISADVANTAGES OF ENGINEERED LUMBER
ADVANTAGES:
PRODUCTIVE USE OF WOOD MATERIALS
USE OF RAPIDLY RENEWABLE MATERIALS
DIMENSIONAL STABILITY
STRUCTURAL STRENGTH
LARGE SIZES AND LONG SPANS (LARGE DEPTHS)
DISADVANTAGES:
ADHESIVES OFF-GASSING
FIRE DANGER
Monday, April 9, 12
WOOD-PLASTIC COMPOSITE DECKING
MADE FROM WOOD FIBERS AND PLASTICS OF VARIOUS TYPES THAT, WITH OTHER CHEMICALS, ARE MOLDED INTO BOARD LIKE SHAPES
CONSISTENT MATERIAL QUALITY
RESISTANT TO MOISTURE
Monday, April 9, 12
NON-STRUCTURAL COMPOSITE LUMBER
MADE FROM BLENDS OF PLASTIC AND WOOD AND QUALITY VARIES WIDELY BY SPECIFIC PRODUCT
OFTEN USED FOR TRIM & SHELVING AND OTHER PAINTABLE SURFACES
EXPANDS AND CONTRACTS MORE WITH MOISTURE
Monday, April 9, 12
PLASTIC LUMBER
MADE FROM 50% OR MORE PLASTIC CONTENT
MADE FROM RECYCLED CONSUMER WASTE (BOTTLES, MILK JUGS, ETC.)
LESS STRUCTURAL VALUE
RESISTANT TO WATER, INSECTS, FADING, ETC.
OFTEN USED FOR DECKING & TRIM
Monday, April 9, 12
WOOD PANEL PRODUCTS
PANEL DIMENSIONS ARE USUALLY 4’X8’
REQUIRE LESS LABOR TO INSTALL BECAUSE THEY ARE IN LARGER PIECES
RESIST SHRINKING, SWELLING, CHECKING AND SPLITTING
MAKE EFFICIENT USE OF FOREST PRODUCTS
Monday, April 9, 12
STRUCTURAL WOOD PANEL PRODUCTS
3 TYPES:
PLYWOOD
COMPOSITE PANELS
NONVENEERED PANELS
Monday, April 9, 12
PLYWOOD
MADE OF THIN LAYERS OF WOOD (VENEERS) GLUED TOGETHER
GRAIN ON FRONT AND BACK RUN IN THE LONG DIRECTION
ONE OR MORE OF THE INTERIOR CROSSBANDS HAS THE GRAIN RUNNING IN THE OPPOSITE DIRECTION
ALWAYS AN ODD NUMBER OF LAYERS IN PLYWOOD
Monday, April 9, 12
COMPOSITE PANELS
HAVE TWO PARALLEL FACE VENEERS BONDED TO A CORE OF RECONSTITUTED WOOD FIBERS
Monday, April 9, 12
NONVENEERED PANELS
ORIENTED STRAND BOARD (OSB) IS MADE FROM LONG SHREDS OF WOOD THAT ARE COMPRESSED AND GLUED INTO THREE TO FIVE LAYERS
OSB STRANDS ARE ORIENTED IS THE SAME MANNER AS THE GRAIN IN PLYWOOD
GENERALLY STRONGER AND STIFFER THAN OTHER TYPES OF NONVENEERED PANELS
Monday, April 9, 12
NONVENEERED PANELS
PARTICLEBOARD IS MADE FROM SMALLER WOOD PARTICLES THAN OSB THAT ARE COMPRESSED AND BONDED (WITH GLUE) INTO PANELS
MANUFACTURED IN DIFFERENT DENSITY RANGES
USUALLY A BASE MATERIAL FOR WOOD VENEERS AND PLASTIC LAMINATES
Monday, April 9, 12
NONVENEERED PANELS
FIBERBOARD IS MADE FROM WOOD FIBERS AND SYNTHETIC RESIN BINDERS
INTENDED FOR INTERIOR USE ONLY
DIMENSIONALLY MORE STABLE THAN PARTICLEBOARD, STIFFER AND BETTER ABLE TO HOLD FASTENERS
MOST COMMONLY “MDF” OR MEDIUM DENSITY FIBERBOARD
Monday, April 9, 12
PLYWOOD PRODUCTION
VENEERS FOR PLYWOOD ARE ROTARY SLICED:
1. LOGS ARE SOAKED IN HOT WATER TO SOFTEN THE WOOD
2. LOGS ARE ROTATED ON A LATHE AGAINST A KNIFE THAT PEELS OFF A THIN VENEER (LIKE PAPER BEING UNWOUND FROM A ROLE)
Monday, April 9, 12
PLYWOOD PRODUCTION
3. STRIP OF VENEER IS CLIPPED AND SENT THROUGH A DRYING KILN (MOISTURE DROPS TO 5%)
4. SHEETS ARE ASSEMBLED INTO LARGER SHEETS AND DEFECTS ARE REPAIRED (PATCHED)
5. A MACHINE SPREADS GLUE ON SHEETS AND THEY ARE ASSEMBLED WITH THE REQUIRED GRAIN ORIENTATIONS
Monday, April 9, 12
PLYWOOD PRODUCTION
6. PRESSES COMPRESS THE STACK WITH PRESSURE AND HEAT TO CREATE DENSE, FLAT PANELS
7. PANELS ARE TRIMMED TO SIZE, GRADED AND GRADE STAMPED
Monday, April 9, 12
PLYWOOD
PLYWOOD COMES IN THICKNESSES OF .25” TO 1.125”
TYPICALLY 4 X 8 FEET IN SIZE, THOUGH USUALLY .125” (1/8) SMALLER THAN NOMINAL DIMENSIONS TO ALLOW FOR EXPANSION DUE TO MOISTURE
Monday, April 9, 12
MEDIUM-DENSITY OVERLAY (MDO)PLYWOOD
FOR AN ESPECIALLY SMOOTH AND DURABLE SURFACE, A RESIN TREATED OVERLAY MAY BE APPLIED ON ONE OR BOTH SIDES
USED FOR CONSTRUCTION OF CONCRETE FORMS, CABINETWORK, FURNITURE, EXTERIOR SIDING
Monday, April 9, 12
MEDIUM-DENSITY OVERLAY (MDO)PLYWOOD
UNLIKE STRUCTURAL PANEL VENEERS, HARDWOOD PLYWOODS INTENDED FOR INTERIOR USE ARE SLICED FROM SQUARE BLOCKS OF WOOD CALLED FITCHES
FITCHED SLICED VENEERS ARE ANALOGOUS TO QUARTERSAWN LUMBER AND RESULT IN A CLOSE GRAIN PATTERN
Monday, April 9, 12
PRESSURE PRESERVATIVE-TREATED LUMBER
DESIGNED TO COUNTERACT SUSCEPTIBILITY TO ATTACK BY DECAY AND INSECTS
PREVIOUSLY CREOSOTE WAS USED (AN OILY DERIVATIVE OF COAL) BUT ODOR, TOXICITY & UNPAINTABILITY HAVE CAUSED IT TO BE INFREQUENTLY USED IN CONSTRUCTION
Monday, April 9, 12
PRESSURE PRESERVATIVE-TREATED LUMBER
CHROMATED COPPER ARSENATE (CCA) WAS ALSO COMMONLY USED, THOUGH RECENT DISCOVERY OF ITS TOXICITY HAS CAUSED IT TO BE PHASED OUT IN FAVOR OF LUMBER TREATED WITH SALTS THAT DO NOT CONTAIN ARSENIC
LONG TERM PROTECTION (30+ YEARS) COMES FROM PRESSURE IMPREGNATION WHICH DRIVES PRESERVATIVES DEEPLY INTO THE FIBERS OF THE WOOD
Monday, April 9, 12
WOOD FASTENERS
FASTENERS HAVE ALWAYS BEEN THE WEAK LINK IN WOOD CONSTRUCTION
TEND TO RELY ON ONE MEMBER BEARING ON ANOTHER
Monday, April 9, 12
WOOD FASTENERS: NAILS
SHARP POINTED METAL PINS THAT ARE DRIVEN INTO WOOD WITH A HAMMER OR MECHANICAL NAIL GUN
NAILS COME IN VARIOUS TYPES
Monday, April 9, 12
WOOD FASTENERS
Monday, April 9, 12
WOOD FASTENERS
Monday, April 9, 12
WOOD FASTENERS
Monday, April 9, 12
SUSTAINABILITY OF WOOD?
DO YOU THINK WOOD IS A SUSTAINABLEBUILDING MATERIAL ?
Monday, April 9, 12