timber in internal applications Material Basics Timber and Wood Products Basic material properties and characteristics.

timber in internal applications 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

timber in internal applications 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

timber in internal applications 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

timber in internal applications Material Basics Variation: fibre & grain The cell structure is designed to serve particular functions in a tree. Its properties vary in different directions. rays cells fibres vessels hardwood earlywood rays latewood softwood

timber in internal applications 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.

timber in internal applications Material Basics Each piece is unique Myrtle burl veneer Quarter sawn hardwood

timber in internal applications Material Basics Properties are variable Drying (seasoning) & shrinkage Strength & hardness Durability Appearance

timber in internal applications Material Basics Moisture and drying in wood cells removed bound water Seasoned timber 15% MC 100% MC Unseasoned timber Growing tree free water 25% MC fibre saturation bound water Partially seasoned timber

timber in internal applications 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

timber in internal applications 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 pineRad 3.5%Tang 4% Hoop pineRad 2.5%Tang 3.5% CypressRad 3.5%Tang 4% Spotted gumRad 4.5%Tang 6% KarriRad 4.5%Tang 10% Sydney blue gumRad 5%Tang 9% Grey IronbarkRad 5.5%Tang 7.5% Mountain ashRad 6.5%Tang 13% Softwood Hardwood Tangential shrinkage Radial shrinkage Longitudinal shrinkage

timber in internal applications Material Basics Shrinkage in sawn sections Tangential shrinkage is the highest; So, the growth rings tend to shorten as the timber dries.

timber in internal applications 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.

timber in internal applications Material Basics Grain, strength & stiffness Direction of grain Strong parallel to grain & stiff parallel to grain Weak perpendicular to grain Properties of the grain

timber in internal applications 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

timber in internal applications 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.

timber in internal applications 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.

timber in internal applications Material Basics Timber products: mouldings Hardwood or softwood. Solid seasoned timber milled to a wide variety of shapes.

timber in internal applications 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

timber in internal applications Material Basics Timber products: curved glulam Glue laminated material can be curved. Curved bar

timber in internal applications 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

timber in internal applications 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.

timber in internal applications 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

timber in internal applications 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

timber in internal applications Material Basics Grading standards AS Timber - Seasoned cypress pine - Milled products AS Timber - Hardwood - Sawn and milled products AS Timber - Softwood - Sawn and milled products

timber in internal applications 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.

timber in internal applications 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

timber in internal applications 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.

timber in internal applications Material Basics AS 2796 Hardwood - Sawn & milled 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.

timber in internal applications 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

timber in internal applications 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.

timber in internal applications Material Basics AS 2796 Hardwood - Sawn & milled 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.

timber in internal applications 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.

timber in internal applications Material Basics Jointing Timber is a highly versatile material that can be shaped and joined easily. Mortice and tenonHoused Half housed

timber in internal applications Material Basics Jointing methods OverlapFixing blocks DowelBiscuit

timber in internal applications 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.