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