KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Content Timber and its properties • Grading for structural applications • Appearance properties • Grading for appearance applications Grading for structural and appearance applications 0.0 title ! www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Grading Grading • For wood products, grading is a process of: • In practice, grading involves separate assessment of: ! sorting a naturally variable material ! into groups with similar structural, visual or other properties ! against established criteria ! through human or mechanical assessment – The properties of the timber in the piece against grade criteria – The quality of the piece’s form as a board or sheet against specific tolerances for warp, wood quality, etc • Specific grade names then identifies the groups – Select, high feature, F8! Hardwood veneer Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Grading – checking tolerances Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Structural grading methods • Grading is based on a correlation between strength and a grading parameter • Visual stress grading Grading timber for structural applications – Assessing of natural characteristics to • AS 2858 for softwood, AS 2082 for hardwood • The results of an in-grade testing program to AS4490 • Machine stress grading – Assessment of stiffness on flat to AS 1748 Assured structural performance is essential for all regulated building applications, and all structural applications are regulated www.csaw.utas.edu.au • Proof grading – Assessment of ability to take a proof load to AS 3519 • Other grading methods • Quality control – Verification of the process and grade properties by testing to AS 4063 Timber and its properties www.csaw.utas.edu.au 1! KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Visual structural grading Species Determine characteristic species strength Testing short clears The piece Visual structural grading Structural capacity Structural grade (visual) The portion of strength in the piece compared to an ideal clear piece • A trained grader examines each piece and assess its characteristics against the structural grade criteria • They assign a structural grade to the piece • This is used widely for hardwood and treated pine products Stress grades Defined sets of structural properties Species strength group Cluster of species with similar strength characteristics Piece assessment - Visual using structural grading standard Grade parameter Piece stress grade (F27, A17, F5, etc) structural properties In-grade testing to determine relationship of the parameter Visual grading Timber and its properties www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Structural grade limit: softwood Machine stress grading Characteristic Limit Pith Permitted if growth rings less than 10mm Surface checks Not to exceed 2mm wide and 600mm long Knots - single or group, knot holes Face: KAR less than 60% in 80% face Edge: KAR less than 66% Other: KAR less than 45% Resin & bark pockets Up to 150mm long and 10mm wide Wane Up to 25% of width of face or edge Spring 70mm: 23mm per 2.4 m 100mm: 15mm per 2.4m Bow 35mm: 45mm per 2.4 m 45mm: 30mm per 2.4m Sloping grain Less than in Seasoned F5 KDA503/335 Timber, its origin and characteristics Species population The piece Structural capacity Grade parameter Stress grades In-grade testing to determine relationship of parameter Defined sets of structural properties Piece assessment - Machine grading using grade parameter Piece stress grade (MGP 12, etc) structural properties Machine graded pine and hardwood relies on a correlation between lowload bending on flat (the minor axis) to other structural properties Excerpt of grading rules from AS 2858 Softwood Timber and its properties www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Machine stress grading Machine stress grading Relies on a correlation between a measured structural property and all others Half span at each end not tested use visual over-ride • Minor axis stiffness most commonly used – each piece tested in non-destructive bending about minor axis over most of its length – minimum E-value determines grade (F-grade or MGP grade) of whole piece – grade stamp often applied by the machine – visual check can over-ride the machine grade TOP TOP TOP TOP TOP Grade MGP12 • More reliable results than visual gradings Commissioning a stress grading machine requires in-grade testing to establish the relationship between the grading parameter and the other structural properties Timber and its properties TOP www.csaw.utas.edu.au Load Feed timber on Flat Timber and its properties www.csaw.utas.edu.au 2! KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Industrial stress grader Data logging from the stress grader Timber and its properties www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Proof grading Proof grading Structural capacity Species population Grade parameters Stress grades In-grade testing to determine relationship of parameters - under design load Structural grade (visual) Significant major axis bending load applied Likely strength in the piece given specific characteristics Initial assessment ss Verified compliance to stress grade Pa The piece Defined sets of structural properties Proof testing This is a grade verification technique • Timber initially sorted using a documented process structural properties Fa il - Visual using structural grading standard Timber and its properties www.csaw.utas.edu.au Grade verified Broken pieces rejected Pieces sold as proof graded timber to AS 3519 If too many pieces fail, producer must adjust initial sorting process Timber and its properties KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Other grading methods Quality Control www.csaw.utas.edu.au • A production process to ensure timber output is consistent with grade marks • Several forms of non-destructive evaluation (NDE) provide useful grading parameters – The velocity of sound or other waves through the piece usefully correlates with density and stiffness – This is commonly used to grade logs and veneer Timber and its properties www.csaw.utas.edu.au • Process Checking - checking • Product Checking - product grading process to ensure that collected and tested to verify all steps are correctly applied properties • Machine control -Verify • AS/NZS 4063 machine settings Verification of properties • Grader qualifications by full scale (in-grade) Checking of grading skills testing - training if required • Third party audit - Independent verification that product matches the stress grade Timber and its properties www.csaw.utas.edu.au 3! KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Product Checking “Special” Jobs • “Special” Jobs - large or important structures may require extra provisions for quality control and reliability – large spans make major members more crucial • Specification – quality control provisions are negotiated as part of specification or purchase contract Product checking applies at several production stages • Every piece is checked for grading mistakes with a visual override • Samples are taken each shift to check stiffness • Periodic in-grade test of sample Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics • Inspection and testing – output sampled and tested Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Appearance applications Appearance properties Except where they perform some structural function, appearance applications are rarely regulated • Applications where the key performance requirements include the utility and visual appeal of surfaces or elements – flooring, lining, cladding; joinery and architectural structures www.csaw.utas.edu.au Timber and its properties KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Performance requirements Consistent doesnt mean even www.csaw.utas.edu.au Utility • Dimensional regularity – Stability, twist, bow, cup, and spring • Resistance to service conditions – Hardness, toughness, durability • Moisture content • Possibly strength or stiffness Visual appeal • Visual consistency in the finished surface from the primary viewing position – Not necessarily colour or feature consistency in the individual board or sheet • Consistency relates to a combination of colour, colour consistency, grain, feature, and surface uniformity in the boards, sheet or finished element Theatre floor and seating Timber and its properties www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au 4! KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Woods appearance properties Wood’s properties Basic Stability Visual Character Density Board stability Colour Feature Hardness Unit shrinkage Colour Clear wood Toughness Grain pattern Colour consistency Gum vein - kino Grain Knots Durability - above ground Texture Insect feature Lyctid resistance Figure Durability Broadly species related Grading for appearance applications Broadly board related Timber and its properties www.csaw.utas.edu.au www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Grading standards Grading to Australian standards • Timber for appearance applications can be graded to: • Australian Standards – flooring, feature timbers – AS 1810-1995 Timber Seasoned cypress pine - Milled products – AS 2796.2-2006 Timber Hardwood - Sawn and milled products – AS 4785.2-2002 Timber Softwood - Sawn and milled products • Industry standards – furniture stock, joinery, cabinetry • Designer specification; or • Personally selected • Each AS standard generally has two sections: – product requirement; & – visual grades Courtesy of Spowers Architects Timber and its properties www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics AS 2796.1 Product requirement AS 2796 Part 1: Distortion tolerances • As feature is identified as a desirable visual characteristic, distortion and machining tolerances are associated with the product group, not the visual grade • The major product groups are: • Tolerances limit board 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 – Joinery and dressed boards; – Strip and overlay flooring, mouldings, sawn boards for feedstock; & – Light decking, lining boards, cladding, facia, bargeboards Timber and its properties www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au 5! KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics AS 2796 Part 1: Product requirement AS 2796 Part 2: Grade rules • Three visual grades are established • Permissible limits listed for each for : Durability • No lyctid susceptible sapwood is allowed Moisture content • The MC anywhere in a piece must be between: – gum vein – knot size & frequency (location unimportant) – splits, cracks, checks (size and frequency) – insect feature – stain (colour), grain uniformity – 9-14% for most products including flooring – 8-13% for parquet & furniture components High Feature: Distinct with a rich, lively & vibrant surface Medium Feature Standard: Increased feature providing a surface with distinct natural appeal Low Feature Select: Straight & even grain with uniform texture Courtesy of Spowers Architects Timber and its properties www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Features AS 4785 Softwood - Sawn & milled • Layout similar to AS 2796 with section on product requirements & visual grades; • Visual grades are: – – – – – Tight gum vein and black spec Timber and its properties www.csaw.utas.edu.au Clear, Appearance, Select, Standard, Utility • With radiata pine, there is a much greater use of industry grades and terms can vary between companies Timber and its properties KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Plywood appearance grades Standards and colour Location grade Appearance grade for plywood for aesthetic applications Face grade A Quality A—a high quality appearance grade, suitable for clear finishing Face grade B Quality S - an appearance grade that permits natural characteristics as a decorative feature Face grade C Quality B - an appearance grade suitable for high quality paint finishing Back grade A Quality C - a non-appearance grade with a solid surface Back grade B Quality D - a non-appearance grade with permitted open imperfections Western red cedar boards www.csaw.utas.edu.au • Colour and colour consistency are critical aspects of visual appeal • However, colour is held to be a characteristic of the species in Australian standards – They does not contain any requirements for colour • Market perceptions control colour variability in supply • Timber can be colour-sorted by agreement between the parties Colour-sorted lining in a court Timber and its properties www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au 6! KDA503/335 Timber, its origin and characteristics KDA503/335 Timber, its origin and characteristics Appearance grading for colour Standards, feature and recovery • In all grading and specification, grade selection is a sustainability issue • All timber includes some natural feature, marks in the wood that portrait aspects of the trees life and history Black spec – These are highly characteristic of species and events • Both the term ‘Select’ and its prevalence in the market can lead to significant under-utilisation of logs and boards Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Hobnail Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Summary Appearance grading • Grading for structural applications – This involves visual, machine stress, proof and other NDE grading in production, coupled with quality processes – Structural grading is required for the use of any wood product in a structure • Appearance properties – Species and board characteristics influence the utility and visual appeal of surfaces and elements • Grading for appearance applications – Visual appearance grading is to one of a variety of methods or standards – Generally, special agreement is required if colour is to be a grade criteria Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Timber and its properties www.csaw.utas.edu.au KDA503/335 Timber, its origin and characteristics Varied applications Thanks to Patrick Cook www.csaw.utas.edu.au Timber and its properties www.csaw.utas.edu.au 7! ... wide Wane Up to 25 % of width of face or edge Spring 70mm: 23 mm per 2. 4 m 100mm: 15mm per 2. 4m Bow 35mm: 45mm per 2. 4 m 45mm: 30mm per 2. 4m Sloping grain Less than in Seasoned F5 KDA503/335 Timber,... properties Timber and its properties TOP www.csaw.utas.edu.au Load Feed timber on Flat Timber and its properties www.csaw.utas.edu.au 2! KDA503/335 Timber, its origin and characteristics KDA503/335... 1810-1995 Timber Seasoned cypress pine - Milled products – AS 27 96 .2- 2006 Timber Hardwood - Sawn and milled products – AS 4785 .2- 20 02 Timber Softwood - Sawn and milled products • Industry standards