1. Final Project - Materials - Wood Flashcards
What material is it?
Strong, durable, lightweight and easy to work with
Wood
Wood: 2 main categories?
- Softwood (conifers: pine, fir, hemlock, spruce)
- Hardwood (hardwood: cherry, maple, oak)
What type of wood is mostly used for: flooring, panelling, furniture and interior trim?
Hardwood
What main property determines the use of wood as a construction material? Why?
Is wood more subject to horizontal or vertical shearing?
- The grain
- A piece of wood is more resistant to tensile and compressive forces when these are oriented parallel to its grain.
- Tensile forces perpendicular to the grain cause the wood to split
- The shear resistance of a piece of wood is greater when it acts perpendicular to its grain rather than parallel. The wood is therefore more subject to horizontal shearing than to vertical shearing.
Why reduce the water content of wood? How to do?
- By drying it in the air or in a dryer under specific conditions of heat, air circulation and humidity.
- To increase the general resistance of the wood, its stability and its resistance to fungi, rotting and insects.
- Wood resists rotting when its water content is less than 20%.
What should be taken into account when cutting and constructing assemblies of wood of any size? (2)
Below a water content of 30%, wood expands when it absorbs water and contracts when it loses it.
It is therefore necessary to take into account these possible shrinkages and swellings.
Name the 3 types of preservatives.
- Water-soluble preservative: gives clean, odorless and easy-to-paint wood. However, exposure to chromium and arsenic can pose a health hazard.
- Oil preservatives: May stain wood, but treated wood can be painted. Very toxic, so not used in building construction.
- Creosote treatment: gives the wood a colored and oily surface and a persistent odor (especially used for installations in aquatic environments)
Which wood preservative treatment is the most effective? Protects what?
The most effective is the pressure treatment, especially when the wood touches the ground.
Wood: what is the nominal dimension?
Refers to the dimensions of a piece of lumber before drying and surface planing.
(The dimensions after planing correspond to the actual dimensions of a piece of construction wood)
Name the 4 main types of wood panels.
- Plywood
- Particle board
- Oriented strand board (OSB)
- Chipboard
Wood : advantages as a building material
- Readily available as a building material
- Lower cost than concrete, masonry, and steel structures
- Stronger in compression than tension
- Heavy Timber resists fire better than unprotected steel
- For improved tension and compression apply load parallel to the grain • For improved shear strength, apply load perpendicular to the grain
Two primary calssifications of softwood lumber
yard lumber: structural purposes and rough framing; further classfied as boards, dimension, and timber
factory and shop lumber: used for making door frames, windows, and finish items
Define board, dimension, and timber when referring to softwood yard lumber
board - less and 2” thick; 2” or more wide
dimension - 2”-5” thick; 4” to 12” or more wide
timber - 5” or more thick; 5” or more wide
Wood that will be seen in finish applications (e.g.: flooring, interior trim, furniture, hardwoods, casework) are sawn from a log in what way?
quartersawn to produce lumber that have annual rings running nearly perpendicular to the face of the piece
Plain-sawn
Quartersawn
Rift-sawn
Plain-sawn grain : growth rings leave irregular shapes *used for rough
Quartersawn: growth rings run parallel to board edges *used for finishing
Rift-sawn: Growth rings run parallel to board edges but more variability
When a tree is cut, the water slowly begins to evaporate in the following order:
- Free Water: water held in the cavities of the cells. Reduces water content to 26% - 32% moisture
- Bound Water: water held in within the cellulose of the cell walls, wood starts to shrink at this point and the strength and stiffness of the wood begins to increase.
Seasoning
• Water content in a piece of wood can vary between 30% - 300% of the oven-dry
weight of the wood. This unseasoned wood is called greenwood.
• Seasoned lumber is stronger and stiffer than unseasoned, more dimensionally
stable, andlighter in weight.
What type of sawing is used mostly in building construction?
• Most lumber intended for use in building framing is plainsawed,
which produces the maximum yield of lumber from a log.
• Some pieces have the rings running perpendicular to the faces
of the piece, some have rings on various diagonals, and some
have rings running parallel to the faces.
• Varying grain orientation cause pieces to distorted differently
during seasoning, or drying, vary differently in their appearance,
and erode at different rates when used as flooring, siding, etc.
Grading
- Each piece of lumber is graded for appearance or structural strength and stiffness at the mill.
- Appearance grading is done visually by trained inspectors. Structural grading is done either visually or by machine.
• •
Lumber is sold by species and grade…. Higher grade = more $$$
Grade stamps are applied to each piece of lumber.
Grade Stamp
to be considered dry lumber, moisture content in wood cannot exceed ____%
19%
to be grademarked kiln dry, moisture content in wood cannot exceed ___%
15%
wood shrinks mostly in which direction relative to its grain?
perpendicular to its grain
pressure treated wood
preservative is forced deep into wood cells
- protects from fungi, moisture, and insects
3 basic types of wood preservative
creosote - distillate of coal tar and is effective protection against insects; insoluable in water; easy to apply; used mainly to protect railroad ties, marine timbers, and roadway guard posts; _not used in building applicatio_ns
oil borne preservative - include pentchlorophenol(penta); used to treat utility poles and cross arms, fresh water pilings, and bridge timbers; applied by brishing, dipping, or pressure treating; generally not used in building application but sometimes used for long span glulams
waterborne preservatives - used in building; include ammoniacal copper quaternary (ACQ); also known as alkaline copper quat, copper azole, and sodium borate (SBX); leave wood paintable; odorless
two chemical wood preservative that aren’t good to use
chromated copper arsenate (CCA), ammoniacal copper zinc arsenate (ACZA)
- harmful to health and environment because of arsenic content
- CCA was phased out by EPA in 2003; chemcials leach out form wood
- ACQ more corrisive than CCA to fasteners and flashing
- aluminium flashing should not be used with these preservative
- preservative with borates will leach out when exposed to moisture; preservative with borates are limited to areas protected from moisture and not in contact with ground
when wood that is treated with preservatives is cut exposed areas should be treated with
a copper naphenate solution containing at least 2 percent copper.
what organization grades finish carpentry lumber
WWPA
Western Wood Products Association
heartwood
wood that comes from the center of the tree
sapwood
wood that comes from the perimeter of the tree
Flitch
Veneer is obtained either by “peeling” the trunk of a tree or by slicing large rectangular blocks of wood known as flitches. The appearance of the grain and figure in wood comes from slicing through the growth rings of a tree and depends upon the angle at which the wood is sliced.
Wane
the presence of bark or absence of wood from any cause on the edge or corner of a piece of lumber
wood deformations
the straightest, most uniform grain appearance in board lumber is achieved by specifying what type of sawn wood?
rift sawing
with rift sawing, each cut for a board is made by sawing a quarter section of a log radially toward the center point of the tree. This requires the quearter section of log being sawn to be shifted slightly for each cut.
- the grain is nearly perpendicular to the face of the board
- this gives the straightest grain pattern
- normally reserved for oak, to reduce appearance of flaking, which is caused by the medullary cells in the oak
rotary slicing is ony used to make…
veneer
Name wood defects
Shake: a lengthwise separation in a piece of rough carpentry occuring between or through the growth rings
Check: a separation of the wood fibers occuring across or through the growth rings
Split: similar to a checkexcept that the separation extends completely through the lumber, usually at the ends
which of the following most affects lumber strength
a. a split
b. a wane
c. a check
d. a shake
a. a split
a split extends completely through the wood so this wood affect both horizontal shear resistance and bending strength. the other defects listed extend only patrially into the wood
the allowable stress ratings for lumber in the building codes are based primarly on
a. size groups
b. species
c. types of defects.
d. all of the above
d. all of the above
Architectural woodwork for installation in the southwest US should have a moisture conent of
a. less than 5%
b. 4%-9%
c. 5%-10%
d. 8%-13%
b. 4%-9%
the southwestern portion of the US is the driest, so moisture content should approximate the conditions in which the lumber will be used. However, it is difficult to reduce the moisture conent below 5%, so option A is an unrealistic answer
it is unrealistic to attempt and dry wood to have a moisture content of less than ___%
5%
wood species highly resistance to decay
black locust
osage orange
red mulberry
yews
wood species resistant to decay
cedars
redwood
white oak
sassafras
junipers
catalpa
baldcypress
(old growth)
wood species moderately resistant to decay
white pine
honey locust
longleaf pine
baldcypress
On APA stamps, an exposure durability rating of “exterior” means…
panels are fully waterproof bonded and deisgned for permanent exposure to weather, when painted or sealed
On APA stamps, an exposure durability rating of “exposure 1” means…
panels have full waterproof bond and are designed for use where long construction delays may occur before panels are protected or where high moisture conditions are expected in service
-these panels are not a substitute for exterior rated panels
On APA stamps, an exposure durability rating of “exposure 2” means…
designed for use in protected construction applications where only moderate exposure to moisture is expected
Difference between platform framing and balloon framing?
Ballon: continuous studs to roof
Platform: studs interrupted @ floors
Typical roof framing members
Ridge beam, Rafters, Battens, etc
What is ice damming?
It occurs when inadequate insulation or major air leaks allow heat from inside the building to escape through the roof and cause melting of snow on the roof. It prevents water to escape the roof - backs up under the shingles and creates potential for leak.
1 - Ceiling insulation location
2 - Skylights away from ice damming areas
3 - Eave protection - type S or M roll roofing laid with joints lapped 4” and cemented together - extending 12” min beyond inside face of the exterior wall and min 36” from the edge.
Types of roof framing, most common
Most common is gable roof
When wood joists are framed into masonry walls, a fire cut is required for wood joists because…
…it prevents the masonry from being pushed up and out if the wood member should collapse during a fire.
saddle hangers
pieces of preformed metal, designed to fit over a beam, that provide support for joists framed perpendicularly to the beam.
- this type of connection hardware allows the joists to be installed with their top edges flush with the top edges of the beams
- it avoids requirement that the joists be placed over the beams, which wold increase the total deph required for the floor structure- reduces depth of the structure
these are used to connect wood structure that must be diassembled
shear plates
NOT split ring connectors
Split Ring Connector
are high capacity connectors used in heavily loaded joints of timber frames and trusses
- Is used in conjunction with a bolt and is inserted in matching circular grooves in the mating pieces of wood.
- It spreads the load across a much greater area of wood than can be done with a bolt alone
plywood used as sheathing is designated 32/16. What does ths mean?
32/16 is the span rating for the plywood sheathng.
- this designation means that the material has been tested according to the standard of the Enigneered WOod Association and can be used to span rafters 32 in on center or joists 16 in on center
- span rating and other information about the material can be found stamped on each sheet of plywood
APA stamp
- APA grade stamps are divided into three classes which outline the sheathing panel’s intended use:
Stud-I-Floor, Rated Siding, Structural I Rated Sheathing and Rated sheathing.
- The number beneath the grade is the span rating. From the APA Guidelines: “The left-hand number is the maximum recommended center-to-center spacing for supports in inches when the panel is used for roof sheathing with the panel’s long dimensions across supports. The right-hand number is the maximum center-to-center spacing of supports in inches when the panel is used for subflooring with the panel’s long dimension across supports. The Span Rating on APA RATED STURD-I-FLOOR and APA RATED SIDING panels appears as a single number. The Span Ratings for APA RATED STURD-I-FLOOR panels, like those for APA RATED SHEATHING, are the maximum recommended center-to-center spacing for supports in inches with the panel’s long dimension or strength axis across three or more supports.” The span ratings are determined by strength and not thickness.
- Bond classification: Here the classification denotes the weather conditions and moisture levels your OSB sheathing panels are designed to withstand. Exposure 1 means the panel is not intended for permanent exposure to the elements but will withstand normal delays in construction.
- Mill Thickness expressed in inches (the thickness category is below #9). The thickness and application will help you establish the proper fastener size and spacing.
- This number identifies the producing mill.
- PS-2 10 is the voluntary standard the panel must meet or exceed.
- OSB sheathing panel face orientation indicator.
LVL (or laminated veneer lumber)
uses the veneers in sheets and looks like thick plywood with no crossbands
“thin glued laminated framing”
Structural Composite Lumber
Made up of ordinary plywood veneers or of long strands of wood fiber
• All grains of all the veneers or strands are oriented in the longitudinal direction of
the piece of lumber to achieve max bending strength.
• It’s stronger, straighter, and more uniform than conventional lumber and less
likely to warp, twist, bow, or shrink
Structural insulated panel (SIP)
composite unit consisting of two outer skins bonded to an inner core of rigid insulating material
- commonly composed of 7/16 OSB
- insulated with molded expanded poly styrene
common coordition concerns for SIPs
- detailing vapor barriers
- providing seismic anchors where required
- detailing termite shield in geographical areas where requried
Glulams are available in 3 appearance grades
industrial - used where appearance is not a primary concern
architactural - used where appearance is a factor but the best grade is not required
premium - finest appearance is important
fingerjointed
short pieces are joined with finger-like projection
-apporpriate for a paint finish where joints will be covered
a. flush construction
b. flush overlay
c. reveal overlay
d. lipped overlay
high rpessure decorative laminate (HDPL)
thin sheet material made by impregnating several layers of kraft paper with phenolic resins and overlaying the paper with a patterned or colored sheet and a layer of melamin resin
in order to get a countertop or cabinet to fit snugly against a slightly irregular partition, which of the following should be specified or called out on the drawings
a. astragal
b. extended frame
c. scribe
d. shoe molding
c. scribe
a scribe is an integral part of woodwork or a separate piece of trim that is cut, sanded, or otherwise shaped on the jobsite to exactly match the irregulatiries of an adjacent material
