Timber Products

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timber in internal applications

Material Basics

Timber and Wood Products

Basic material properties and characteristics.

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Material Basics

The nature of timber

• Timber is a natural product, drawn from the wood in the trunks of trees.

• Its character is consistent with the species of tree and the form and growth over time of the wood 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 - can’t 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 particular functions in a tree.

• Its properties vary in different directions.

rays

rays

cells

fibres

vesselshardwood earlywood

rays

latewood

softwood

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Material Basics

Variation: species & growth

• Species and genetics: – selected stock or

natural seed.

• Climate:– wet or dry, cold or

warm.

• Arrangement:– native forest or

plantation.

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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

removed bound waterSeasoned

timber15% MC

100% MC

Unseasoned timber

Growingtree

free water

25% MC

fibre saturation

bound waterPartially seasoned

timber

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Material Basics

Benefits of drying

• Drying timber increases its:– strength; – stiffness; – stability– durability; &– ease of fastening.

• It is ideally dried to a moisture content in equilibrium with its service 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 equilibrium with 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%

So

ftwo

od

Ha

rdw

ood

Tangential shrinkage

Radialshrinkage

Longitudinalshrinkage

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Material Basics

Shrinkage in sawn sections

• Tangential shrinkage is the highest;

• So, the growth rings tend 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 can

be as low as a week.

• Hardwoods have a non-porous cell structure:– 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 and

colour• Its strength is dependant on the

properties of the wood and the slope of the 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 of products and species including: – Solid sawn, moulded and laminated timber;– Veneer;– Plywood; and– Wood panels.

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Material Basics

Timber products: sawn

• Hardwood or softwood.

• Solid timber cut from a log and dried.

• It is a versatile material used for moulding, frames and exposed structures.

• Size is restricted.

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Material Basics

Timber products: mouldings

• Hardwood or softwood.

• Solid seasoned timber milled to a wide variety of shapes.

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Material Basics

Timber products: glue laminated

• Small pieces of timber glued together to form a larger element.

• Used as both a structural and finishing element.

• Size is limited only by transport capacity.

bench top

beam

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Material Basics

Timber products: curved glulam

• Glue laminated material can be curved.

Curved bar

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Material Basics

Timber products: veneer

• Thin layers of solid wood sliced from a flitch or peeled from a log and dried.

• High quality material is used as a decorative finish.

• Lower grade material is used to make plywood, LVL and similar products.

Veneer leaf

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Material Basics

Timber products: plywood

• Layers of veneer glued together so that the grain direction alternates between layers.

• Usually produced in sheets.

• Very good in a structure, as a lining and as a flooring surface.

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Material Basics

Timber products: wood panels

• Panels made from wood or wood fibres bound together with glue, or other binder:– Particleboard– Medium Density

Fibreboard (MDF)– Hardboard– Core board

MDF sheet

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Material Basics

Appearance grading

• Production process of sorting products into groups with similar characteristics & properties.

• Timber identified by calling up a specific grade.

Visual grading

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Material Basics

Grading standards

• AS 1810-1995 Timber - Seasoned cypress 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 requirements for hardwood used for visual applications: 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 select grade– uniform wood with

few natural features

• Through to high feature grade– including lively

natural feature as part of a desirable aesthetic.

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Material Basics


• Tolerances are established for the major product 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 on thickness

• Spring - dependent on width

• Twist - separate limits for less or more than 25 mm thick

• Cup - 1mm per 100 mm width

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Material Basics

AS 2796 Part 1

• No lyctid susceptible sapwood is allowed. (Lyctids are small wood eating insects.)

• MC anywhere in a piece must be between:– 9-14% for most products including flooring. – 8-13% for parquet & furniture components.

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Material Basics


• The standard recognises feature as a desirable visual characteristic;

• Therefore, distortion and machining tolerances are associated with product, not grade; &

• The timber can then be specified with the desired appearance for any function.

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Material Basics

AS 4785 Softwood - Sawn & milled

• Layout is similar to AS 2796 with product requirements & visual grades;

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

• With radiata, there is a much greater use of industry grades; &

• Terms can vary between companies.

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Material Basics

Jointing

• Timber is a highly versatile material that can be shaped and joined easily.

Mortice and tenon Housed

Half housed

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Material Basics

Jointing methods

Overlap Fixing blocks

DowelBiscuit

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Material Basics

Conclusions

• Timber is a natural product.

• It has been used for centuries.

• Skilled use and understanding of the material can yield excellent results.

Business

Timber Products