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Chapter

Building Materials

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Objectives

Describe the hardwood and softwood classifications.
Define moisture content (M.C. and E.M.C.).
Identify common defects in lumber.
Define lumber grading terms.
Calculate lumber sizes according to established industry standards.
Explain plywood, OSB, hardboard, and particleboard grades and uses.

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Objectives (Cont.)

List precautions to observe while working with treated lumber.
Identify types of engineered lumber and list their uses and advantages.
Discuss the uses of light gage steel framing.
Identify a variety of metal framing connectors and indicate where each is used.
Identify nail types and sizing units.

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Lumber

Natural or engineered sawmill products

Boards used for flooring, sheathing, and trim
Dimension lumber
Timbers used for posts, beams, and stringers
Specialty items

Andy Dean Photography/Shutterstock.com

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Wood Structure and Growth

Wood contains narrow cells called fibers or tracheids
Lignin holds cells together
Cambium is layer of cells just inside bark

N.C. Brown Center for Ultrastructure Studies, State

University of New York, College of Environmental

Science and Forestry, Syracuse, NY

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Annular Rings

Growth layers that form each season
Sapwood

Contains living cells
May be several inches thick

Heartwood

Formed as sap becomes inactive

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Kinds of Wood

Softwood comes from evergreen trees

Douglas fir
Southern pine

Hardwood comes from broadleaf (deciduous) trees

Beech
Cherry

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Cutting Methods

Softwood

Flat-grained
Edge-grained

Hardwood

Plain-sawed
Quarter-sawed

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Moisture Content and Shrinkage

Moisture content is percent of oven dry weight

Free water
Bound water
Fiber saturation point

Wood shrinks most along direction of annual rings

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Equilibrium Moisture Content

Point at which moisture in wood is balanced with that in air
Moisture content (MC) is always changing
MC varies in different geographical areas

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Seasoning Lumber

Seasoning

Reducing MC of lumber to required level
Air drying
Kiln drying

Moisture content of wood can be determined

Oven drying sample
Using electronic moisture meter

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Lumber Defects

Irregularities occurring in or on wood
Reduce wood’s strength, durability, or usefulness
May detract from or improve the wood’s appearance

Western Wood Products Assn.

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Lumber Grades

Softwood grades

Boards
Dimension
Timbers
Factory and shop lumber

Hardwood grades

Firsts and seconds
Selects
Common

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Lumber Sizes

Nominal dimension is

Always used
Rough unfinished measurement (width and thickness)
Greater than dressed size

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Calculating Board Footage

Board foot is unit of measure for lumber
Formula for board feet

T is thickness of board (in.)
W is width (in.)
L is length (ft.)

bd. ft. = No. pcs. × T × W × L

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Panel Materials

Plywood

Thin sheets laminated to various thicknesses

Composite plywood

Veneer faces bonded to wood cores

Nonveneered panels

Particleboard
Fiberboard
Oriented strand board

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Grade-Trademark Stamp

Quality grades for plywood

Lettering system indicates veneer quality
Name indicates intended use or “performance rating”
APA trademark and grade stamp

APA-The Engineered Wood Association

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Exposure Ratings

Two basic categories

Exterior type, 100% waterproof glueline
Interior type, moisture-resistant glueline

Durability classifications

Exterior: Fully waterproof adhesives
Exposure 1: Waterproof bond
Exposure 2: Interior type with intermediate glue

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Span Ratings of Plywood

Span rating

Maximum center-to-center distance between supports

Example

Sheathing may have span ratings of 24/0, 24/16, 40/20, or 48/24

APA-The Engineered Wood Association

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MDO and HDO Plywood

MDO

Exterior-type panel with 100% waterproof adhesive
Readily accepts paint

HDO

Made with thermosetting resin-impregnated fiber surface
More rugged than MDO

APA-The Engineered Wood Association

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Hardwood Plywood Grades

Numbering system for faces and backs of panels
Symbols to indicate grade
Core constructions

Veneer core
Lumber core

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Oriented Strand Board

Made of individual flakes of wood
Parts adhered to each other with resins and glues
Approved for variety of construction projects

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Composite Board

Made of reconstituted wood with veneer on either side
Widely used in modern construction

Sheathing
Subflooring
Siding
Interior wall surfaces

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Particleboard

Used in cabinetwork

Drawer bottoms
Concealed panels in cases and chests

Made of wood flakes, chips, and shavings
Bonded together with resins or adhesives
Used as base for veneers and laminates

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Hardboard

Made of refined wood fibers
Pressed together to form hard, dense material

Standard
Tempered

Tempered hardboard is filled with oils and resins

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Wood Treatments

Pressure-treated lumber

Resists termites and fungal decay
Used for outside jobs

Identifying end tag or stamp
Major types of liquid preservatives

Waterborne
Oilborne
Creosote

Southern Pine Council

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Safety Note

Environmental Protection Agency (EPA) warning

Treated wood should never be used where waterborne arsenical preservatives in treatment may become component of food, animal feed, or drinking water

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Handling and Storing Lumber

Piles of framing lumber and sheathing

Place on level skids raised above ground
Cover with canvas, waterproof paper, or polyethylene film

Wood panels

Stack on level surface
Keep ventilated

Finish lumber

Open-stack with wood strips for air circulation
Handle with care to prevent soiling and scarring

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Engineered Lumber

Wood structural units altered through manufacturing processes
Stronger, straighter, and more dimensionally stable than sawn lumber
Components glued together in different configurations

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Laminated-Veneer Lumber

Produced much like plywood
Used as headers, beams, and columns
Remains stable with predictable performance
Can be stained or left exposed

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Glue-Laminated Beams

Also called glulams
Made by gluing and applying pressure to layers
Come in two types

Balanced
Unbalanced

Made in custom and stock sizes

Rik Vandermeulen, Unalam

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I-Joists

Have “I” shape
Consist of flanges of structural composite lumber
Light, straight, and strong
Can have knockouts for plumbing and electrical services

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Open-Web Trusses

Sometimes used in place of floor joists
Fabricated in factories from solid 2 × 4 lumber
Allow installation of pipes and wiring via open webs

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Parallel-Strand Lumber

Made of 1″ by 8′ strands of veneer coated with adhesive
Veneer strips form billets of various lengths
Lumber yards cut billets to specified lengths
Can be pressure-treated for outdoor use

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Laminated-Strand Lumber

Made of strands of wood bonded with polyurethane adhesive
Available in two thicknesses: 1 1/4″ and 3 1/2″
Examples of use

Door and window headers
Rim joists in floors
Core stock for flush doors with veneer overlays

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Thinking Green

Cutting custom and fabricated components at lumber mill

Reduces jobsite waste
Eliminates poor storage and other mishaps
Reduces carpenter errors

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Light Gage Steel Framing

Found in light commercial buildings and residential construction
Attached to base and ceiling channels with screws
Used for partitions and nonloadbearing walls

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Metal Framing Connectors

Stamped brackets or strapping designed to make connections

Wood-to-wood
Wood-to-masonry
Wood-to-concrete

Tension bridging
Metal corner braces

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Nails

Available in range of types and sizes

Common
Box
Casing
Finish
Brad

Come in size units called penny (abbreviated d)

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Screws

Greater holding power than nails
Often used for interior construction
Classified by

Shape of head
Surface finish
Material from which they are made

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Concrete

Used in foundations and slab-on-grade construction
Combination of several materials

Portland cement
Sand
Crushed stone
Water

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Adhesive Bonding Agents

Carpenters use several bonding materials

Glues come from natural materials
Adhesives are developed from synthetic materials
Cements and mastics are rubber-based

Some have longer curing times than others
Joints may need to be clamped securely during curing time

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Safety Note

Never use flammable contact cement in building with open flames

Space heater
Kitchen range pilot light
Furnace

Fumes are very flammable and may result in explosion

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Mastics

Include waterproofing materials and adhesives

Liquids
Pastes

Vary in characteristics and application methods
Usually packaged in metal or plastic containers or in gun cartridges

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Open Time

Amount of time between spreading material and when parts must be clamped
Also called setting time
Varies with temperature and humidity
Adhesives easily spread at open times as indicated by manufacturer

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Staples

Used as fasteners for various applications
Applied with

Pneumatic staplers
Electric staplers
Hand staplers

Available in various lengths, widths, and thicknesses (gages)
Come in different point types

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