Glencoe: Section 61 Flashcards
Lumber Defect:
Flaw that detracts from the quality of wood in either appearance of usefulness
How many characteristics are considered when wood is graded?
25
Warp:
any variation from a flat surface
It includes:
Bow, Crook, and Cup
Carpenters can cut flawed 2x4 into
blocking
The width and thickness of lumber given by two types of measurements:
Nominal and actual dimensions
Nominal:
size of the board in inches as originally cut in width and thickness, not its length.
After the board has been surfaced and seasoned at the mill, its X
actual dimensions become less than its nominal dimensions.
Building codes use X dimensions
actual dimensions
Dressed sizes apply:
after the wood has shrunk and been surfaced with a planning machine
2x4 actually measured in dressed size:
1 1/2 x 3 1/2
Why have sized of lumber been standardized?
Convenience in ordering and handling
Softwood lumber is readily available in actual lengths of
8’, 10’, 12’, 14’ and 16’
Common Nominal dimensions of softwood:
2”, 4”, 6”, 8”, 10”, 12” in width
1”, 2”, 4”, 6” in thickness
Are hardwoods standardized for length or width
no
Hardwood thicknesses:
1/4”, 1/2”, 1”, 1 1/4”, 1 1/2”, 2”, 2 1/2”, 3”, 4”
2x4 is actually
2x10 is actually
once you get into 2 x 8 you
1 1/2 x 3 1/2
1 1/2 x 9 1/4
drop to a quarter
The united states is the only lumber producing country that does not
use metric system.
Wood imported using metric have these dimensions
thickness and width in MM
length in meters
Wane:
– The presence of bark, or the lack of wood from any cause, on the edge or corner of a piece of lumber.
Bow:
A flatwise deviation (bend) along the grain from a straight true surface. Bow is measured at the point of greatest deviation.
Crook:
an edgewise deviation (bend) from a straight, true surface. rook is measured at the point of greatest deviation.
Cup:
flatwise deviation (deviation) across the grain from a straight true surface, cup is measured at the point of greatest deviation.
Check:
Small crack that runs across the growth rings. Occurs as result of seasoning
Shake
lengthwise grain separation through or between growth rings. May be further classified as ring shake or pitch shake
Split:
Lengthwise separation extending from one surface through the piece of lumber to the opposite side or an adjoining piece
Decay:
Disintegration of wood due to the action of wood destroying fungi (dot, rot, unsound wood)
Knot
Place where branch once grew. Classified according to size, quality, and occurrence. Measured by averages.
Knothole
left by the removal of an embedded knot
pitch
accumulation of resin in the wood cells
Stain
discoloration on or in lumber other than its natural color
Torn grain
torn spots created as the broad is machined to size
Decay and damage by insects to wood is most likely to occur when:
wood is wet
A house must be designed to encourage rain water to
drain away
Water vapor is given off when
cooking, washing or other household activities
Water vapor can do what to a house
pass through walls, ceilings, when it reaches a cold surface it forms water droplets.
Sources of water in homes:
rain, water activities in homes, leaking pipes.
What can allow water into homes:
gaps in exterior wood trim or between a chimney and siding
Wood will not rot if
it is kept dry
Fungi needs:
air, warmth, food (wood), moisture
Dry rot
An advanced type of decay where wood is Brown and crumbly. Wood may also be white and spongy
Decay wood is often indicated by
sunken areas on surface or a hollow sound when wood is tapped with hammer.
Fungi can grow on surface of wood if
air around is very damp
Fungi grow most rapidly between
70f and 85f
Moisture content of X or less is generally dry enough to stop fungi
20% or less
When untreated, sap wood of all common native woods
have low resistance to decay
Natural decay resistance of native woods lies in the
heartwood
Of the commonly used species in household construction, which wood has high resistance to decay
Bald cypress, redwood, and various cedars
Why is heartwood becoming harder and harder to obtain
increasing amounts of timber are cut from the smaller trees of second growth stands in which little heartwood has developed.
When decay resistant woods is needed
Preserve treated wood is used
Insects that damage wood:
termites, carpenter ants, and beetles
Termites:
termites are the most destructive of the insects that infest wood.
Best way to protect against termites:
during planning and construction: remove all woods debris such as stumps and lumber scraps from the soil before and after construction. Also NO WOOD MEMBERS SHOULD BE IN CONTACT WITH SOIL
Forms of termite protection:
chemical termiticide, physical barriers and treated wood
Two types of termites:
Subterranean and dry-wood
Subterranean termites:
account for 95 percent of termite damage. They eat the interior of wood and cause most damage before they are detected. They effect Hawaii and southern 2/3 of united states. They thrive in moist warm soil containing food. They build shelter tubes over foundation walls and pipes about 1/4 to 1/2 inch.
Two types of termite blocking methods:
Metal shields 12” min above ground, and covered soil.
Most destructive termite:
Formosan termite
Dry wood termites:
Fly directly to the wood instead of building tunnels from the ground. Less destructive
Carpenter ants:
Northeast, northwest, midwest.
Nest in ground as well as dead trees, firewood, and houses. Do not eat wood but plant juices, insects honey and food particles.
How do carpenter ants damage wood:
irregular tunnels they create for their nests.
What indicates a carpenter ants presence
small sawdust particles.
Control for carpenter ants:
chemicals
Two types of beetles that cause damage to wood:
powderpost and deathwatch
Powderpost:
Enter house via already infested wood, only attack hardwood
Deathwatch:
eats both soft and hard wood
Carpenter bees:
cut 1/2” diameter hole in bare or untreated wood. Build nests by boring tunnels.
Lumber can be treated with:
Liquid wood preservatives soon after being milled
Wood preservative:
a chemical that protects wood
Most common treated wood
Fir, spruce, and pine generally used outdoors or where in contact with concrete or masonry
Ways of preservative treating wood
Injection, dipping and drying, chemicals forced into wood under pressure
Preservative treated wood is:
graded and stamped to indicated its suitability for various uses
Preservative can accelerate
metal corrosion, so special fasteners may be needed.
Fire retardant treated wood
do not stop wood from burning but can limit the amount the fire spreads.
Moisture content of fire retardant treated wood
lumber is dried to 19%
plywood dried to 15% or less.
Can i modify fire retardant treated wood?
yes. It can be cut to length, drilled and lightly sanded. However ripping and surfacing and milling operations are only permitted in certain cases.
Today, both types of these woods are used in construction:
Solid wood and engineered wood.
Engineered panel:
any manufactured sheet product, including plywood, which is made of wood or wood pieces bonded with a natural or synthetic adhesive.
Plywood
a building material that consists of layers of wood veneer and sometimes other materials that have been glued together.
Light but strong.
Unlike solid lumber, plywood comes in
large sheets called panels that can be installed quickly
Other popular panel products other than plywood are made out of
wood flakes, dust, or fibers mixed with adhesives or Portland cement.
All manufactured panels including plywood share these characteristics:
Engineered for the efficient use of wood resources.
Manufactured using various natural or synthetic adhesives.
Performance is predictable.
Uses of plywood:
Made into foundation forms providing stiff uniform surface for concrete
Plywood floor wall and roof sheathing stiffens and strengthens structure of house.
Smooth easy to paint surface
Underlayment, plywood makes a strong smooth substrate for finish flooring
Cabinets and built ins are made of it because it host fasteners well and accommodates various types of joinery.
Types of plywood:
Structural plywood and hardwood
Structural plywood:
Used where strength is more imporatant than looks, sheathing and subflooring and concrete forms.
Hardwood plywood:
Used for paneling, cabinets, and other interior features
Plywood consists of layers of
wood veneer and sometimes other materials that have been glued together.
Wood veneer:
very thin, pliable sheet of wood that has been sawed, peeled, or sliced from a log.
Plies:
when wood veneer sheets are used in ply wood.
Plywood is manufactured with X number of layers that:
odd number of plies layers that run at 90 degree angle from neighboring layers. May have 3 5 or 7 layers. Grains of outmost layers runs in same direction.
Face Ply and Core Ply
Face plies are the two outer ply layers. Core ply are inner.
The best quality face ply is called the front, the lesser quality is caleld the back.
Plies that are arranged at 90deg angles are called
crossbands.
Lumbercore plywood
Veneers bonded to a core of glued up lumber or particle core
Hardwood ply may be made entirely out of
veneers
How Plywood is Manufactured:
After a tree is cut it:
is trucked to the plywood mill and stored into a pond.
Only select logs qualify as
peeler logs
How Plywood is Manufactured:
Chosen log is lifted from pond and
cut to length
How Plywood is Manufactured:
As log cut to length moves to the mill it is
debarked by high pressure jets
How Plywood is Manufactured:
After debarked
log is lifted into a lathe which slices continuous strips of veneer from the log.
How Plywood is Manufactured:
After veneering
it moves to clipping machine where giant knives cut into a specific width
How Plywood is Manufactured:
After clipping
Sent to the dryer to reduce moisture
How Plywood is Manufactured:
After dryer
natural defects in the veneer sheets are cut out and holes are patched with solid wood or synthetic patching material. Some sheets then go to the glue spreader where large rollers cover both sides with adhesives.
How Plywood is Manufactured:
After natural defects are removed and some are glued
Glued and unglued sheets and stacked alternatively together to make the desired thickness. This is called the Lay Up process
How Plywood is Manufactured:
After Lay Up
Panels are bonded together using pressure and sometimes heat. The panels are trimmed to exact length and thickness and blemishes are repaired. They are then graded.
How plywood is graded:
grade marks are stamped on the back face of plywood. Grade identify all features of panel.
Two methods of grading plywood:
Prescriptive and Performance
Prescriptive plywood grading:
panel is graded by the quality of its veneer, adhesive used to assemble it, number of layers(plies) and dimensions.
Performance plywood grading:
panel is rated according to its suitability for a particular use. Like moisture resistance.
Hardwood plywoods are graded primarily by
veneer quality, species, and arrangement of face plies.
In prescriptive grading, wood species are divided into five groups based on
strength.
In prescriptive grading, describe how to veneer grade is printed
“A - B” format.
Front face - back face grade.
Panel made with rater resistant adhesive is followed by an
X
Elements of a plywood grade stamp
Grade of veneer front and back panel Species group Type (interior exterior) Type of glue Product standard governing manufacturer mill number sometimes application (siding) and identification index.
Composite Panel Product:
made from pieces of wood in a variety of forms, including veneer, chips, and fibers. The wood is mixed with adhesives and formed into panels. Share many of the same characteristics as plywood.
Most common types of Composite Panel Product
Oriented-strand board (OSB), hardboard, medium-density fiberboard. (MDF), and particleboard.
Chipboard, waferboard, flakeboard
all names for panels that are essentially the same or similiar to OSB
Com-ply
panel developed by APA (The Engineered Wood Association). Compressed wood strands core with veneer wood faces.
Eco advantage of composite panels?
Made from otherwise useless wood. Small trees or unsound wood.
Two strong influences on the properties of composite panels are
The size and shape or individual flakes and particles.
The ratio of adhesive to particles.
Most adhesives in composite panels are
water proof such as Urea-formaldehyde. Trend toward developing other adhesives because of health concerns towards off gassing.
Why is wax(0.5% to 1%) added to panels?
What else is added sometimes
to reduce moisture absorption and make it suitable for sheathing.
Fire retardant chemicles
Difference between ply-wood and composite panels?
The way the wood is processed.
In composite, logs or woodscraps are processed mechanically to create small unform pieces. Mixed with adhesive then squeezed under pressure to create sheets.
Then finished or treated.
Most common panel size:
4’ x 8’ but panels go up to 8 ‘ x 16’
Concerns about using future composites
Each new product adds chemicals not found in solid wood. Therefore consider the health and environmental effects. And review the material safety data sheet.
composite panels are free from
cracks and other imperfections found in solid or veneered wood.
Use blades with X when cutting composite panels
carbide
The absence of voids gives composites X
full uniform contact surface for gluing.
OSB
oriented strand board is made from wood strands bonded with adhesive under heat and pressure.
Strands in each layer run more or less in the same direction and then layers are placed perpendicular to each other. 3 to 5 layers usually.
OSB is available with X grove edges.
square or tongue and groove edges.
Thickness of OSB
3/8” to 1 1/8”
OSB are not suited for
long term exposure to weather.
To increase moisture resistance what is done to OSB
edges are coated at the factory with sealant.
Which is most likely to swell or shrink in response to humidity, OSB or Plywood:
OSB
OSB sheathing and subflooring should be installed with a X gap between the ends of adjacent panels and Y at the sides.
1/8”
1/4”
What happens if the edge seal of OSB panel is damaged.
Moisture can wick into the panel and swell the edges.
How should OSB panels be stores on the jobsite
off the ground stacked and supported by 4x4 stringers or other blocking. Covered loosely so as not to trap moisture. Steel binding that secures panels during delivery should be cut right away to stop damage if swelling
Fiberboard
logs are chipped into small pieces of wood that are then reduced to fibers by steam or mechanical processes. Fibers are refined and mixed with an adhesive and compressed.
Fiberboard generally includes panel products such as
hardboard and medium density fiberboards
Hardboard:
high density fiberboard.
Slurry (mixture of fibers and water) is formed into a mat. Mat is compressed under several stages of pressure to form the final panel
Hardboard is available in what grades?
Standard and tempered.
Standard is given no additional treatment
tempered is given linseed oil or tung oil prior to pressing to increase stiffness and water resistance.
S1S and S2S
hardboard with 1 side smooth
hardboard with 2 sides smooth
Hardboard available thicknesses
1/8” and 3/8”
Standard Hardboard panel sizes
4’ x 8’ but up to 6’ x 16’
Perforated Hardboard
closely spaced holes drilled or punched into it.
hardboard can be printed to X
match grains of oak and walnut or other woods
Medium-density fiberboard
uniform compressed wood fibers mixed ueraformaldehyde adhesive. Smooth surface. Manufactured similar to particleboard.
Why should protection when working cutting or sanding composite products
fine dust
Particle board
combining wood particles or flakes with adhesives and hot-pressing them into panels. Particles near top and bottom are fine and coarser ones are located near core.
Is particle board weaker or stronger than OSB
weaker
Where is particle board used?
indoor wherever smooth and inexpensive material is needed.
Particle board standard sizes
1/4” to 1 1/2” thick and from 3’ to 8’ wide and up to 24’ length
How many different grades of Particle board are there?
How many densities?
ten.
three (high, medium, and low)
Fiber-cement Board
Cellulose fibers are bound together with a mixture of Portland cement, ground sand, additives and water.
Benefits of fiber-cement board
non-combustible and rot proof.
Fiber-cement board standard sizes
5/16’ thick.
Comes in sheets of 4’wide and 8’,9’,10’, or 12’ long.
One side is rough, other is smooth.
What board is desirable for siding?
Fiber-cement board because its smooth finish and stability.
Fiber cementboard should be stored
level dry surface. Keep corners from being struck.
Carry panel on edge by two people.
Breathing excessive amounts of silica dust can lead to
Silicosis
Engineered lumber
any manufactured product made of solid wood, wood veneer, wood pieces, or wood fibers in which components have been bound together with adhesives.
Pros of Engineered lumber products
Stiff, strong, dependable, and versitile.
- Uses wood that would have otherwise been waste
- Predictable performance
- Available in wide variety of dimensions
- Free of defects found in regular lumber
Engineer lumber products include:
Laminated-veneer header and I-joists Glue-laminated beams Finger-jointed studs Laminated-strand lumber posts Oriented-strand lumber window framing stock
Where should engineered lumber not be used
where it will be permanently exposed to weather. Should not be in direct contact with concrete or masonry.
LVL
laminated veneer lumber is a family of lumber products made with wood veneer as the basic element. Lightweight, rigid and available up to 66’
How is LVL made
Layers of veneer are glued together in various ways.
How is LVL different from plywood
LVL is used for beams and headers and joists instead of panels.
LVL has parallel lamination so each layer runs in the same direction as opposed to ply woods perpendicular lamination
How are LVL products made:
Sheets of veneer are moved through drying ovens, till moisture content is 8%. It is checked and graded
Goes to glue spreader. Top is coated.
Highest grade veneers are placed on top and bottom of stack.
Pressure and heat applied to cure adhesive. Final material is called a billet, which may be up to 80’ long.
Finished LVL products are typically shipped to dealer in X’ increments
60’
Dealer of LVL cuts the LVL in X’ increments
2’
