WOOD CONSTRUCTION Uses and Characteristics Types of Wood Manufacturing Process (milling & seasoning) Part 1 Professor Brandi R. Shepard© ACH 121-Materials and Methods 1

Sustainability in Wood Construction Only major renewable structural material Forestry Practices Sustainable forestry Clearcutting & replanting Mill Practices – Lumber Recovery Factor (LRF) Transportation Embodies Energy Content Construction Process

Only major renewable structural material

Forestry Practices

Sustainable forestry

Clearcutting & replanting

Mill Practices – Lumber Recovery Factor (LRF)

Transportation

Embodies Energy Content

Construction Process

CHARACTERISTICS OF WOOD Qualities of Wood High strength relative to it’s weight In compression & tension Bending & resistance to impact Easy to work with Simple tools to create desired shapes Highly durable Excellent insulating qualities Fastened quickly & economically Recyclable Biodegradable Renewable Resource

Qualities of Wood

High strength relative to it’s weight

In compression & tension

Bending & resistance to impact

Easy to work with

Simple tools to create desired shapes

Highly durable

Excellent insulating qualities

Fastened quickly & economically

Recyclable

Biodegradable

Renewable Resource

CHARACTERISTICS OF WOOD Undesirable Qualities of Wood Not perfectly straight nor precise Size & shape affected by moisture Contains growth defects Can spilt & warp Burns easily Decays Susceptible to Insect Damage

Undesirable Qualities of Wood

Not perfectly straight nor precise

Size & shape affected by moisture

Contains growth defects

Can spilt & warp

Burns easily

Decays

Susceptible to Insect Damage

USES OF WOOD Structural Light-wood framing Heavy-timber framing Non-Structural Interior partitions (studs), blocking Finished Carpentry Flooring, panels, moldings, shelving Architectural Woodwork Cabinetry/Furniture, drawers, cornices, mantels

Structural

Light-wood framing

Heavy-timber framing

Non-Structural

Interior partitions (studs), blocking

Finished Carpentry

Flooring, panels, moldings, shelving

Architectural Woodwork

Cabinetry/Furniture, drawers, cornices, mantels

TYPES OF WOOD Hardwoods “ Leafy” (oak, cherry, etc.) Deciduous (loses leaves) Overall generally stronger Grow slower $$$$ cost more Used for trim lumber Flooring, cabinetry/furniture, interior paneling

Hardwoods

“ Leafy” (oak, cherry, etc.)

Deciduous (loses leaves)

Overall generally stronger

Grow slower

$$$$ cost more

Used for trim lumber

Flooring, cabinetry/furniture, interior paneling

TYPES OF WOOD Softwoods “ Needles” (evergreens) Non-deciduous (does not lose leaves) Called “conifer”, bears cones Overall generally weaker Grow quicker & Cost less Used for framing lumber Sheathing (roofing & exterior panels) Types of trees SPF (spruce-pine-fir) Hem-fir (hemlock & fir) Yellow pine

Softwoods

“ Needles” (evergreens)

Non-deciduous (does not lose leaves)

Called “conifer”, bears cones

Overall generally weaker

Grow quicker & Cost less

Used for framing lumber

Sheathing (roofing & exterior panels)

Types of trees

SPF (spruce-pine-fir)

Hem-fir (hemlock & fir)

Yellow pine

SOFTWOODS 75% lumber in country Fir, white pine, hemlock, cedar, aspen, spruce, cypress HARDWOODS Grows mostly in central region Maple, birch, beech, ash, cherry, poplar, walnut, oak, hickory

SOFTWOODS

75% lumber in country

Fir, white pine, hemlock, cedar, aspen, spruce, cypress

HARDWOODS

Grows mostly in central region

Maple, birch, beech, ash, cherry, poplar, walnut, oak, hickory

PARTS OF A TREE (wood growth) Pith: absolute center of tree Heartwood: inactive cells that provide structural support for tree Cambium layer: 3-5 cell thick zone of active cell growth just beneath the inner bark Sapwood: carries sap (food) from roots to leaves Fig. 6.1-3

Pith: absolute center of tree

Heartwood: inactive cells that provide structural support for tree

Cambium layer: 3-5 cell thick zone of active cell growth just beneath the inner bark

Sapwood: carries sap (food) from roots to leaves

PARTS OF A TREE (wood growth) Rays: run perpendicular to fibers and carry food across the grain; these produce the decorative grain effects Inner bark: carries food (oxygen) from leaves to tree & roots) Outer bark: dry, dead tissue; protects tree Growth ring: made up by summer wood & spring wood; shows age of tree in years

Rays: run perpendicular to fibers and carry food across the grain; these produce the decorative grain effects

Inner bark: carries food (oxygen) from leaves to tree & roots)

Outer bark: dry, dead tissue; protects tree

Growth ring: made up by summer wood & spring wood; shows age of tree in years

Tree Composition Bark Cambium Sapwood Heartwood Pith

Bark

Cambium

Sapwood

Heartwood

Pith

Tree Cells Primarily Hollow, Cylindrical Cells Axis running parallel to the tree (grain direction) Tough Cellulose bound by Lignin Impacts the properties of wood

Primarily Hollow, Cylindrical Cells

Axis running parallel to the tree (grain direction)

Tough Cellulose bound by Lignin

Impacts the properties of wood

Professor Brandi R. Shepard© ACH 121-Materials and Methods 1

Tree Growth Springwood (earlywood) Faster growth Cells larger and less dense Summerwood (latewood) Slower growth Cells smaller and denser

Springwood (earlywood)

Faster growth

Cells larger and less dense

Summerwood (latewood)

Slower growth

Cells smaller and denser

GROWTH CHARACTERISTICS Knots Formed by branches Shakes Grain separation between growth layers Pitch Pockets Grain separation that contains solid or liquid resin

Knots

Formed by branches

Shakes

Grain separation between growth layers

Pitch Pockets

Grain separation that contains solid or liquid resin

MANUFACTURING PROCESS Sawing, edging and trimming logs into square or rectangular pieces of wood Yard lumber Boards Sheathing, siding, flooring, paneling, trim, patterned millwork Dimension Stock Light framing, joists, planks, roof & floor decking Timbers Posts, beams, stringers

Sawing, edging and trimming logs into square or rectangular pieces of wood

Yard lumber

Boards

Sheathing, siding, flooring, paneling, trim, patterned millwork

Dimension Stock

Light framing, joists, planks, roof & floor decking

Timbers

Posts, beams, stringers

MANUFACTURING PROCESS Trees are cut and transported to mill Logs are cut into shorter lengths Cut to fit machinery or to certain length Logs are sent through debarker Bark is removed by peeling, scraping or blasting using high-pressure water jets Log is sent through a headsaw Circular saw or band saw

Trees are cut and transported to mill

Logs are cut into shorter lengths

Cut to fit machinery or to certain length

Logs are sent through debarker

Bark is removed by peeling, scraping or blasting using high-pressure water jets

Log is sent through a headsaw

Circular saw or band saw

MANUFACTURING PROCESS Rough cants, timbers, planks & boards are sent through an edger Removes rounded edges Rips lumber into desired width Lumber is then moved onto trimmer Saws trim off rough ends & defects Next step is green chain, where edged, trimmed lumber are sorted visually According grade, species and size

Rough cants, timbers, planks & boards are sent through an edger

Removes rounded edges

Rips lumber into desired width

Lumber is then moved onto trimmer

Saws trim off rough ends & defects

Next step is green chain, where edged, trimmed lumber are sorted visually

According grade, species and size

MANUFACTURING PROCESS Plainsawing: Better yield from the log Cheaper (better yield) Uneven grain patterns Uneven shrinkage (warps) Used for framing lumber Quartersawing: Less yield from the log Expensive (less yield) Even grain patters Even shrinkage (no warps) Used for trim lumber Milling

Plainsawing:

Better yield from the log

Cheaper (better yield)

Uneven grain patterns

Uneven shrinkage (warps)

Used for framing lumber

Quartersawing:

Less yield from the log

Expensive (less yield)

Even grain patters

Even shrinkage (no warps)

Used for trim lumber

Typical Sawing Method Typical Sawing of a Large Log

Typical Sawing Method

MANUFACTURING PROCESS After sawmilling, lumber is seasoned. Kiln-dried or air-dried Drying Effects Shrinkage Reduced weight Increase of strength and stiffness More dimensional stable

After sawmilling, lumber is seasoned.

Kiln-dried or air-dried

Drying Effects

Shrinkage

Reduced weight

Increase of strength and stiffness

More dimensional stable

MANUFACTURING PROCESS Moisture Content: Amount (percentage) of moisture (water) in the lumber More moisture, more shrinkage!! Shrinkage creates problems!! A N D Seasoning

Moisture Content:

Amount (percentage) of moisture (water) in the lumber

More moisture, more shrinkage!!

SEASONING- Shrinkage Heartwood: oldest and strongest part of the tree More shrinkage PERPENDICULAR to the grain Lumber defects Warps Cracks in finish work Checks

Heartwood: oldest and strongest part of the tree

More shrinkage PERPENDICULAR to the grain

Lumber defects

Warps

Cracks in finish work

Checks

SEASONING- Shrinkage Lumber Defects Crook Cup Twist Bow Splits Checks These are called seasoning defects

Lumber Defects

Crook

Cup

Twist

Bow

Splits

Checks

SEASONING- Moisture Content Moisture content varies 26-32% when cut 19% MAXIMUM for framing-”kiln-dried” 15% when shrinkage is a concern Over 19% moisture content is considered “GREEN” (not good…)

Moisture content varies

26-32% when cut

19% MAXIMUM for framing-”kiln-dried”

15% when shrinkage is a concern

Over 19% moisture content is considered “GREEN” (not good…)

MANUFACTURING PROCESS Lumber is then sent to planing mill Sizing and surfacing Then graded, tallied and prepared for shipment Rough sawn (not surfaced) Purpose for surfacing Smooth Dimensional precision Surfacing typically performed after drying

Lumber is then sent to planing mill

Sizing and surfacing

Then graded, tallied and prepared for shipment

Purpose for surfacing

Smooth

Dimensional precision

Surfacing typically performed after drying

Additional Resources The Encyclopedia of Wood by: Aidan Walker Check out class WebCT site: Articles from Fine Homebuilding Magazine Website links

Check out class WebCT site:

Articles from Fine Homebuilding Magazine

Website links