1a Material Basics

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timber in internal applications

Material Basics

Timber and Wood Products

Basic material properties andcharacteristics.


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Material Basics

The nature of timber

Timber is a naturalproduct, drawn fromthe wood in thetrunks of trees.

Its character isconsistent with thespecies of tree andthe form and growth

over time of thewood in it.

Regrowth in a native forest


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Material Basics

Tree growth

New wood on outside of tree oldest wood on the inside

youngest wood on the outside

diameter largest at the base

one ring (layer) per growing season

Tree in forest grows toward light trunk is straight

lower branches die

leaving small knots in wood

Bark protects wood from damage the tree sheds bark each year


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Material Basics

Production of wood

Cambium - growth cells wood cells created on the inside bark cells created on the outside

Sapwood - newest wood on the outside of tree (~ 1-3 cm) takes nutrients from root to leaves

Heartwood - older wood cells closed - cant pass nutrients storage for waste - extractives

Pith - the start of growth in the tree the original sapling


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Material Basics

Variation: fibre & grain

The cell structure is designed to serve particularfunctions in a tree.

Its properties vary in different directions.

rays

rays

cellsfibres

vessels

hardwood earlywoodrays

latewood

softwood


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Material Basics

Variation: species & growth

Species andgenetics:

selected stock ornatural seed.

Climate: wet or dry, cold or

warm.

Arrangement:

native forest orplantation.


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Material Basics

Each piece is unique

Myrtle burl veneer

Quarter sawn hardwood


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Material Basics

Properties are variable

Drying (seasoning) & shrinkage Strength & hardness

Durability

Appearance


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Material Basics

Moisture and drying in wood cells

removedboundwaterSeasoned

timber15% MC

100% MC

Unseasonedtimber

Growingtree

free water

25% MC

fibre saturation

bound waterPartiallyseasoned

timber


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Material Basics

Benefits of drying

Drying timberincreases its: strength;

stiffness;

stability

durability; &

ease of fastening.

It is ideally dried to amoisture content inequilibrium with itsservice environment.

Checking the moisture content


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Material Basics

Timber shrinks as it dries

It shrinks at different rates in

different directions.

Once dry, it will expand &contract to be in equilibriumwith changing local conditions.

Shrinkage from 12% to 25% MC

Radiata pine Rad 3.5% Tang 4%Hoop pine Rad 2.5% Tang 3.5%Cypress Rad 3.5% Tang 4%

Spotted gum Rad 4.5% Tang 6%Karri Rad 4.5% Tang 10%Sydney blue gumRad 5% Tang 9%Grey Ironbark Rad 5.5% Tang 7.5%Mountain ash Rad 6.5% Tang 13%

Tangentialshrinkage

Radialshrinkage

Longitudinalshrinkage


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Material Basics

Shrinkage in sawn sections

Tangential shrinkageis the highest;

So, the growth ringstend to shorten as the

timber dries.

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Material Basics

Timber dries at different rates

Pines have a porous cell structure: They can be dried very quickly.

Turnaround time from saw to store canbe as low as a week.

Hardwoods have a non-porous cellstructure: The moisture must diffuse through the

cell wall.

Drying can be very slow.

It must be done carefully.

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Material Basics

Grain, strength & stiffness

Direction of grain

Strong parallel to grain & stiff parallel to grain

Weak perpendicular to grain

Properties of the grain

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Material Basics

Summary of characteristics

Timber is a natural material

Each piece is unique in fibre, texture andcolour

Its strength is dependant on the

properties of the wood and the slope ofthe grain

It takes up and gives up moisture

It expands and shrinks as it does so It deteriorates in line with exposure

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Material Basics

Timber products

Timber is available in a wide range ofproducts and species including:

Solid sawn, moulded and laminated timber;

Veneer;

Plywood; and

Wood panels.



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Material Basics

Timber products: sawn

Hardwood orsoftwood.

Solid timber cut froma log and dried.

It is a versatilematerial used formoulding, frames andexposed structures.

Size is restricted.



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Material Basics

Timber products: mouldings

Hardwood orsoftwood.

Solid seasonedtimber milled to a

wide variety ofshapes.



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Material Basics

Timber products: glue laminated

Small pieces oftimber gluedtogether to form alarger element.

Used as both astructural andfinishing element.

Size is limited only

by transportcapacity.

bench top

beam



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Material Basics

Timber products: curved glulam

Glue laminatedmaterial can becurved.

Curved bar



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Material Basics

Timber products: veneer

Thin layers of solid

wood sliced from aflitch or peeled from alog and dried.

High quality materialis used as adecorative finish.

Lower grade materialis used to makeplywood, LVL andsimilar products.

Veneer leaf



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Material Basics

Timber products: plywood

Layers of veneer

glued together sothat the graindirection alternatesbetween layers.

Usually produced insheets.

Very good in astructure, as a liningand as a flooringsurface.



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Material Basics

Timber products: wood panels

Panels made fromwood or wood fibresbound together withglue, or other binder:

Particleboard Medium Density

Fibreboard (MDF)

Hardboard

Core board

MDF sheet



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Material Basics

Appearance grading

Production processof sorting productsinto groups withsimilar

characteristics &properties.

Timber identified bycalling up a specific

grade.

Visual grading



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Material Basics

Grading standards

AS 1810-1995 Timber - Seasonedcypress pine - Milled products

AS 2796-1999 Timber - Hardwood -Sawn and milled products

AS 4785-2002 Timber - Softwood -Sawn and milled products



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Material Basics

AS 2796 Hardwood - Sawn & milled

This standard defines the requirementsfor hardwood used for visualapplications: architectural (flooring, etc),lining & cladding; &

It is in two main sections:

product requirements; &

visual grades.



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Material Basics

Appearance grading - rules

Establish permissible limits on: gum vein

knot size & frequency (location unimportant)

splits, cracks, checks (size and frequency)

stain (colour), grain uniformity

utility: want, wane, cup, bow, spring, twist



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Material Basics

Grade range

From selectgrade uniform wood with

few natural features

Through to highfeaturegrade including lively

natural feature aspart of a desirableaesthetic.



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Material Basics


Tolerances are established for the majorproduct groups (not grades):

Joinery and dressed boards;

Strip and overlay flooring, mouldings, sawn

boards for feedstock; &

Light decking, lining boards, cladding, facia,bargeboards.



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Material Basics

AS 2796 Part 1 - distortion

Bow - depends onthickness

Spring - dependent onwidth

Twist - separate limitsfor less or more than25 mm thick

Cup - 1mm per 100mm width



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Material Basics

AS 2796 Part 1

No lyctid susceptible sapwood isallowed. (Lyctids are small wood eating insects.)

MC anywhere in a piece must bebetween:

9-14% for most products including flooring.

8-13% for parquet & furniture components.



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Material Basics


The standard recognises feature as adesirable visual characteristic;

Therefore, distortion and machiningtolerances are associated with product,not grade; &

The timber can then be specified withthe desired appearance for any function.



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Material Basics

AS 4785 Softwood - Sawn & milled

Layout is similar to AS 2796 with productrequirements & visual grades;

Visual grades are Clear, Appearance,Select, Standard, Utility Grade;

With radiata, there is a much greater useof industry grades; &

Terms can vary between companies.



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Material Basics

Jointing

Timber is a highlyversatile materialthat can be shapedand joined easily.

Mortice and tenon Housed

Half housed



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Jointing methods

Overlap Fixing blocks

DowelBiscuit



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Conclusions

Timber is a natural product.

It has been used for centuries.

Skilled use and understanding of the

material can yield excellent results.



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1a Material Basics