TIMBER FRAMING USING AS 1684.2 SPAN TABLES AS 1684 Teaching Guide TIMBER FRAMING USING AS 1684.2 SPAN TABLES

AS 1684-2010 Residential timber-framed construction Go to www.education.WoodSolutions.com.au for up to date teaching resources including an annotated copy of the standard. This powerpoint presentation is part of a series that has been revised to reflect the requirements of AS 1684 Parts 2 & 3 – 2015 Edition. Some major changes to this edition include amendments to wall nogging requirements, inclusion of ring beam systems and an Appendix of building practices for engineered wood products (EWPs). The MGP span tables provided with the Standard have also been amended.

the timber framing standard AS 1684 RESIDENTIAL TIMBER-FRAMED CONSTRUCTION the timber framing standard Currently you should be using the 2015 Edition.

TIMBER-FRAMING STANDARD AS 1684 TIMBER-FRAMING STANDARD Provides the building industry with procedures that can be used to determine building practice to design or check Construction details, determine member sizes and bracing and fixing requirements for timber framed construction in Non-Cyclonic areas (N1 – N4).

AS 1684.2 – CD Span Tables AS 1684 TIMBER-FRAMING STANDARD Contains a CD of Span Tables (45 sets in all) for wind zones N1 - N4 for the following timber stress grades: Unseasoned Softwood: F5, F7 Seasoned Softwood: F5, F7, F8 MGP10, MGP12, MGP15 Unseasoned Hardwood: F8, F11, F14, F17 Seasoned Hardwood: F14, F17, F27

TIMBER-FRAMING STANDARD AS 1684 TIMBER-FRAMING STANDARD Each set of Span Tables contains 53 separate design tables

TIMBER-FRAMING STANDARD AS 1684 TIMBER-FRAMING STANDARD Using AS 1684 you should be able to design or check virtually every member in a building constructed using timber framing.

First floor wall frames AS 1684 TIMBER-FRAMED CONSTRUCTION Ridge beam Battens Rafters Hanging beams Ceiling Ceiling battens First floor wall frames Roofing External cladding Floor joists Ceiling battens Flooring Lintel Wall frame Wall stud Internal cladding Floor joists Flooring Bearers Stumps or piles

AS 1684 Scope and Limitations WHERE CAN AS1684 BE USED?

Physical Limitations - AS 1684 Physical Limitations - Plan: Rectangular, square or “L”-shaped Storeys: Single and two storey construction Pitch: 35o max. roof pitch Width: 16m max. (between the “pitching points” of the roof, i.e. excluding eaves) 1 6 . m ax W 16.0 m max. W 1 6 . m a x

Physical Limitations - Width Width AS 1684 Physical Limitations - Width Width The geometric limits of the span tables often will limit these widths.

Physical Limitations – Wall Height AS 1684 Physical Limitations – Wall Height Wall Height The maximum wall height shall be 3000 mm (floor to ceiling) as measured at common external walls (i.e. not gable or skillion ends).

Design Forces on Buildings AS 1684 Physical Limitations – Design Forces on Buildings Design Forces on Buildings AS1684 can be used to design for Gravity Loads (dead & live) and wind loads. Suction Internal pressure Suction (uplift) Wind LIVE LOADS (people, furniture etc.) DEAD LOAD (structure) Construction loads (people, materials) (a)  Gravity loads (b)  Wind loads

Wind Classification AS 1684 Wind Classification Non-Cyclonic Regions A & B only N1 - W28N 100km/h gust N2 - W33N 120km/h gust N3 - W41N 150km/h gust N4 - W50N 180km/h gust

Wind Classification AS 1684 Wind Classification Wind Classification is dependent on : Building height Geographic (or wind) region (A for Victoria) Terrain category (roughness of terrain) Shielding classification (effect of surrounding objects) Topographic classification (effect of hills, ridges, etc.)

Wind Classification – Simple References Geographic Region A Site Location Top ⅓ of hill or ridge Below top ⅓ of hill or ridge Suburban site Not within two rows of: City or Town perimeter (as estimated 5 years hence) Open areas larger than 250,000 m2 N2 N1 Less than 250m from: the sea open water wider than 250m N3 Within two rows of: Rural areas

AS 1684 Using Span Tables Design fundamentals & basic terminology Roof framing Wall framing Floor framing (Click on arrow to move to section required)

AS 1684 Using Span Tables DESIGN FUNDAMENTALS & BASIC TERMINOLOGY

Design Fundamentals AS 1684 SPAN TABLES Design Fundamentals – Load Path Design Fundamentals You build from the Bottom up. But you design from the Roof down because loads from above can impact on members below. So start with the roof and work down to the ground level.

Design Fundamentals – Load Path AS 1684 SPAN TABLES Design Fundamentals – Load Path Understanding the concept of a ‘load path’ is critical. Loads need to be supported down the building to the ground. Indirect Load path due to cantilever Roof Load Ground level

Design Fundamentals – Load Path AS 1684 SPAN TABLES Design Fundamentals – Load Path As a general rule it is necessary to increase the timber member size when: Load increases (a function of dead, live, wind loads). Span increases (a function of load paths across openings). Indirect load paths occur (e.g. cantilevers and offsets). Indirect Load path due to cantilever Roof Load Ground level It is possible to decrease timber member size when: Sharing loads across many members. Using members with higher stress grades.

Design Fundamentals – Load Distribution Loads distributed AS 1684 SPAN TABLES Design Fundamentals – Load Distribution Loads distributed Loads are distributed equally between Points of Support. Of the total load on Member X one half (2000 mm) will be supported by the beam or wall at “A” and the other half (2000 mm) will be supported by the beam or wall at “B”. B A MEMBER X

Design Fundamentals – Load Distribution AS 1684 SPAN TABLES Design Fundamentals – Load Distribution If Member X is supported at three or more points it is assumed that half the load carried by the spans either side of supports will be distributed equally. MEMBER X A A B B C C Beam A will carry 1000 mm of load Beam B will carry 3000 mm (1000 mm plus 2000 mm on other side) Beam C will carry 2000 mm

Terminology - Span and Spacing AS 1684 SPAN TABLES Terminology – Span Terminology - Span and Spacing Span is the “face-to-face” distance between points capable of giving full support to structural members or assemblies. Joist Span (between internal faces of these support members). Bearers and Floor Joists

Terminology – Single Span AS 1684 SPAN TABLES Terminology – Single Span The span of a member supported at or near both ends with no immediate supports. This includes the case where members are partially cut through over intermediate supports to remove spring.     

Terminology – Continuous Span AS 1684 SPAN TABLES Terminology – Continuous Span The term applied to members supported at or near both ends and at one or more intermediate points such that no span is greater than twice another. NOTE: The design span is the average span unless one span is more than 10% longer than another in which case the design span is the longest span.

Example: Continuous Span AS 1684 SPAN TABLES Continuous Span Example Example: Continuous Span Span 1 (2000 mm) Span 2 (3925 mm) 1/3 (2000 mm) The center support must be wholly within the middle third. 6000 mm 75 mm Span 2 is not to be greater than twice Span 1. This span is used to determine the size using the Continuous Span tables.

Terminology – Rafter Span and Overhang AS 1684 SPAN TABLES Terminology - Rafter Span and Overhang Terminology – Rafter Span and Overhang Rafter spans are measured as the distance between points of support along the length of the rafter and NOT as the horizontal projection of this distance. Rafter

Terminology - Span and Spacing AS 1684 SPAN TABLES Design Fundamentals – Spacing Terminology - Span and Spacing Spacing is the centre-to-centre distance between structural members unless indicated otherwise. Joist Spacing (Centreline-to-Centreline) Bearers and Floor joists Bearer Spacing (Centreline-to-Centreline).

Terminology – Wall Construction AS 1684 SPAN TABLES Terminology – Wall Construction Terminology – Wall Construction Loadbearing wall A wall that supports roof loads, floor loads or both. Non-Loadbearing internal wall A wall that does not support roof or floor loads but may support ceiling loads and act as a bracing wall. The main consideration for a non-loadbearing internal wall is its stiffness (i.e. resistance to movement from someone leaning on the wall, doors slamming shut etc.).

Terminology – Roof Construction AS 1684 SPAN TABLES Terminology – Roof Construction Terminology – Roof Construction Coupled Roof - rafters are tied together by ceiling joists so that they cannot spread.

Terminology – Roof Construction AS 1684 SPAN TABLES Terminology – Roof Construction Non-coupled roof - a pitched roof that is not a coupled roof. It includes cathedral roofs and roofs constructed using ridge and intermediate beams Such roofs rely on ridge and intermediate beams to support the centre of the roof. These ridge and intermediate beams are supported by walls and/or posts at either end.

AS 1684 SPAN TABLES Using Span Tables ROOF FRAMING

Roof Framing – Typical Basic Roof Shapes AS 1684 SPAN TABLES Roof Framing – Typical Basic Roof Shapes The “footprint” of a building generally consists of a rectangular block or multiple blocks joined together. Roof shapes are made to cover the footprint while also providing sloping planes able to shed water. Hip Gable (Cathedral or flat ceiling) Skillion Hip and valley Dutch Hip (or Dutch Gable)

AS 1684 SPAN TABLES Roof Framing – Typical Members

Roof Framing - Transferring loads to Pitched Roof AS 1684 SPAN TABLES Roof Framing - Transferring loads to Pitched Roof 3. Rafters – take batten loads and transfers them to the support structure below e.g. walls. 1. Roofing material - takes live/dead/wind loads and transfers them to the Battens. 2. Battens - takes roofing loads and transfers them to the Rafters/Trusses. Support wall

Roof Framing – Batten Design AS 1684 SPAN TABLES Roof Framing – Batten Design Typical Process Step 1: Determine the wind classification to factor in wind loads (e.g. assume non-cyclonic winds N1 or N2) Step 2: Determine type of roof (e.g. tiled or sheet.) Step 3: Determine batten spacing – typically 330 mm for tiles, or 450, 600, 900, 1200 mm sheet Step 4: Determine batten span – this will be the supporting rafter spacing. Batten Span Spacing

Roof Framing – Batten Design AS 1684 SPAN TABLES Roof Framing – Batten Design Step 5: Look up relevant Batten Span Table (i.e. non-cyclonic winds N1 and N2) in AS1684 Vol. 2. Step 6: Choose a table reflecting preferred stress grade. Step 7: Select column in the table for the previous batten “spacing and span” assumptions.

Roof Framing – Batten Size Example AS 1684 SPAN TABLES Roof Framing – Batten Size Example Inputs required Wind Classification = N2 Timber Stress Grade = F8 Roof Type = Steel Sheet (20 kg/m2) Batten Spacing = 900 mm Batten Span = 900 mm

Roof Framing – Batten Size Example AS 1684 SPAN TABLES Roof Framing – Batten Size Example 2006 Simplify table Wind Classification N2 Roof Type - Steel Sheet (20 kg/m2) Timber Stress Grade F8 A 38 x 75 mm F8 Batten Is adequate Batten Spacing = 900 mm Batten Span = 900 mm

Rafter Design - Cathedral Roof Scenario AS 1684 SPAN TABLES Rafter Design - Cathedral Roof Scenario Step 1: Determine the wind classification to factor in wind loads. For this example assume non-cyclonic winds N1 or N2. Step 2: Determine dead/live loads on rafters . For this example assume loads are as for a tiled roof with battens (e.g. 60kgs/m2) Step 3: Determine the rafter span. For the example assume a 2100 mm single rafter span. Step 4: Determine the rafter overhang which creates a cantilever span adding extra load. For the example assume a 500 mm overhang. Step 5: Determine the rafter spacing as this determines how much roof loads are shared between rafters. For the example assume a 600 mm spacing . Ridge beam O v e r h a n g Rafter span Rafter Spacing

Rafter Design - Cathedral Roof Scenario AS 1684 SPAN TABLES Rafter Design - Cathedral Roof Scenario Step 6 Look up AS1684 Vol 2 Step 7 Choose table reflecting preferred stress grade Step 8 Determine which column in table to select using the previous “rafter spacing” and “single span” assumptions. Step 9 Go down the column until reaching assumed 2100 mm rafter span and 500 mm overhang Step 10 Check the spans work with assumed roof load of 60kgs/m2 Step 11 Read off rafter size – 90x45mm

Rafter Design - Cathedral Roof Scenario AS 1684 SPAN TABLES Rafter Design - Cathedral Roof Scenario Inputs required Wind Classification = N2 Stress Grade = F8 Rafter Spacing = 900 mm Rafter Span = 2200 mm Single or Continuous Span = Single Roof Mass (Sheet or Tile) = Steel Sheet (20 kg/m2)

Determine Rafter Size Simplify table A 100 x 50mm F8 rafter 2006 Simplify table Maximum Rafter or Purlin Span & Overhang (mm) Inputs required Wind Classification = N2 Stress Grade = F8 Single or Continuous Span = Single Rafter Spacing = 900 mm Rafter Span = 2200 mm Roof Mass (Sheet or Tile) = Steel Sheet (20 kg/m2) A 100 x 50mm F8 rafter is adequate At least 2200mm

Single or Continuous Span AS 1684 SPAN TABLES Ceiling Joist Design Ceiling Joist Design Ridge board Ceiling Joist Rafter Design variables Timber Stress Grade Ceiling Joist Spacing Ceiling Joist Span Single or Continuous Span

Ceiling Joist Design Example AS 1684 SPAN TABLES Ceiling Joist Design Example Ceiling Joist Design Inputs required Wind Classification = N2 Stress Grade = F17 Overbatten = No Single or Continuous Span = Single Joist Spacing = 450 mm Ceiling Joist Span = 3600 mm

ceiling joist is adequate Ceiling Joist Size 2006 Simplify table Inputs required Wind Classification = N2 Stress Grade = F17 Overbatten = No Single or Continuous Span = Single Joist Spacing = 450 mm Ceiling Joist Span = 3600mm At least 3600mm A 120 x 45mm F17 ceiling joist is adequate

Other Members And Components - Ridge board Ridge board AS 1684 Span Tables Other Members And Components - Ridge board Ridge board Some members do not have to be designed using span tables. They are simply called up or calculated based on members framing into them.

Roof Member Load Impacts AS 1684 Span Tables Roof Member Load Impacts The loads from roof members often impact on the design of members lower down in the structure. This impact can be determined from the following load sharing calculations: Roof Load Width (RLW). Ceiling Load Width (CLW). Roof area supported.

Roof Member Load Impacts – Roof Load Width AS 1684 Span Tables Roof Member Load Impacts – Roof Load Width RLW is the width of roof that contributes roof load to a supporting member. It is used as an input to Span Tables for: Floor bearers. Wall studs. Lintels. Ridge or intermediate beams. Verandah beams. Roof Load Widths are measured on the rake of the roof.

AS 1684 Span Tables Roof Member Load Impacts – Roof Load Width

Roof Member Load Impacts – With Trusses AS 1684 Span Tables Roof Member Load Impacts – With Trusses RLW wall B = RLW wall A =

Roof Member Load Impacts – Without Ridge Struts AS 1684 Span Tables Roof Member Load Impacts – Without Ridge Struts For a pitched roof without ridge struts it is assumed that some of the load from the un-supported ridge will travel down the rafter to walls 'A' and 'B'. The RLWs for walls A & B are increased accordingly. RLW wall A = RLW wall B =

Roof Member Load Impacts – With Ridge Struts AS 1684 Span Tables Roof Member Load Impacts – With Ridge Struts x Underpurlin 1 = 2 Underpurlin 2 = 3 y Underpurlin 3 = 3 y

Roof Member Load Impacts – Ceiling Load Width AS 1684 Span Tables Roof Member Load Impacts – Ceiling Load Width Ceiling load width (CLW) is the width of ceiling that contributes ceiling load to a supporting member (usually measured horizontally). A B x CLW

Roof Member Load Impacts – Ceiling Load Width AS 1684 Span Tables Roof Member Load Impacts – Ceiling Load Width CLW is used as an input to Span Tables for hanging beams and strutting/hanging beams Strutting beam span Ridgeboard Underpurlin Strutting beam Roof strut Hanging Beam Strutting/Hanging Beam

Roof Member Load Impacts – Ceiling Load Width AS 1684 Span Tables Roof Member Load Impacts – Ceiling Load Width FIGURE  2.12   CEILING LOAD WIDTH (CLW) CLW Hanging beam D = CLW Strutting/Hanging beam E =

Roof Member Load Impacts – Roof Area Supported AS 1684 Span Tables Roof Member Load Impacts – Roof Area Supported Example: The Strutting Beam Span Table requires a ‘Roof Area Supported (m2)’ input. The strutting beam shown supports a single strut that supports an underpurlin. The ‘area required’ is the roof area supported by the strut. A A/2 B/2 B This is calculated as follows:- Roof Area Supported = Sum of half the underpurlin spans either side of the strut (A/2) multiplied by the sum of half the rafter spans either side of the underpurlin (B/2).

Strutting Beam Design Example AS 1684 Span Tables Strutting Beam Design Example Inputs required Wind Classification = N2 Stress Grade = F8 Roof Area Supported = 6m2 Strutting Beam Span = 2900 mm Single or Continuous Span = Single Roof Mass (Sheet or Tile) = Steel Sheet (20 kg/m2)

Strutting Beam Design Example AS 1684 Span Tables Strutting Beam Design Example Roof Area Supported = 6m2 Roof = Sheet Strutting Beam Span = 2900 mm 2 x 140 x 45 mm F17 members are adequate

AS 1684 Span Tables Wall Framing Return to menu WALL FRAMING

AS 1684 Span Tables Wall Framing Return to menu

Wall Studs Design Example AS 1684 Span Tables Wall Studs Design Example Return to menu Inputs required Wind Classification = N2 Stress Grade = MGP10 Notched 20 mm = Yes Stud Height = 2400 mm Rafter/Truss Spacing = 900 mm Roof Load Width (RLW) = 5000 mm Stud Spacing = 450 mm Roof Type = Steel Sheet (20 kg/m2)

Wall Framing – Wall Stud Size 2006 Simplify table At least 5000mm Inputs required Wind Classification = N2 Stress Grade = MGP10 Notched 20 mm = Yes Stud Spacing = 450 mm Roof Type = Steel Sheet (20 kg/m2) Rafter/Truss Spacing = 900 mm Roof Load Width (RLW) = 5000 mm Stud Height = 2400 mm 70 x 35mm MGP10 wall studs are adequate

Top Plate Design Example AS 1684 Span Tables Top Plate Design Example Return to menu Inputs required Wind Classification = N2 Stress Grade = MGP10 Rafter/Truss Spacing = 900 mm Roof Load Width (RLW) = 5000 mm Stud Spacing = 450 mm Roof Type = Steel Sheet (20 kg/m2)

MGP10 top plates are adequate Wall Framing – Top Plate Size 2006 Simplify table At least 5000mm Inputs required Wind Classification = N2 Stress Grade = MGP10 Roof Type = Steel Sheet (20 kg/m2) Rafter/Truss Spacing = 900 mm Tie-Down Spacing = 900 mm Roof Load Width (RLW) = 5000 mm Stud Spacing = 450 mm 2 x 35x 70mm MGP10 top plates are adequate

Wall Framing – Wall Lintel Design Example AS 1684 Span Tables Wall Framing – Wall Lintel Design Example Inputs required Wind Classification = N2 Stress Grade = F17 Opening size = 2400 mm Rafter/Truss Spacing = 900 mm Roof Load Width (RLW) = 2500 mm Roof Type = Steel Sheet (20 kg/m2)

Wall Framing – Lintel Size 2006 Simplify table Inputs required Wind Classification = N2 Stress Grade = F17 Roof Type = Steel Sheet (20 kg/m2) Roof Load Width (RLW) = 2500 mm Rafter/Truss Spacing = 900 mm Opening size = 2400 mm A 140 x 35mm F17 Lintel is adequate Use 3000mm Use 1200mm

AS 1684 Span Tables Floor Framing Return to menu FLOOR FRAMING

Floor Framing – Floor Members AS 1684 Span Tables Floor Framing – Floor Members Floor joists Floor bearers Platform Floor Sheets Perimeter Brickwork

Floor Framing – Floor Bearers AS 1684 Span Tables Floor Framing – Floor Bearers Bearers are commonly made from hardwood or engineered timber products and are laid over sub-floor supports. Bearers are sized according to span and spacings – typically a 1.8m (up to 3.6m) grid Bearer Span Bearer Spacing

Floor Framing – Floor Load Width Example AS 1684 Span Tables Floor Framing – Floor Load Width Example If a = 900 mm x = 2000 mm y = 4000 mm FLW A = 1900 mm FLW B = 3000 mm FLW C = 2000 mm

Floor Framing – Bearer and Floor Joist Example AS 1684 Span Tables Floor Framing – Bearer and Floor Joist Example Simple rectangular shaped light-weight home Gable Roof =25o pitch Steel Sheet = 20 kg/m2 Wind Speed = N2 Wall Height = 2400 mm 3600 Section Floor joists Bearers 4500 Elevation

Floor Framing – Bearer Design Example AS 1684 Span Tables Floor Framing – Bearer Design Example 25o Floor Load Width (FLW) Bearers at 1800 mm centres FLWA = 1800/2 = 900 mm Bearer A Supports both a Roof Load Floor Joists at 450 mm crs And a floor load 3600 Section 1800

Floor Framing – Bearer Design Example AS 1684 Span Tables Floor Framing – Bearer Design Example Roof Load Width (FLW) for Wall A = a = 496 mm x = 1986 mm Total RLW On Wall A = 1986 mm (say 2000 mm) + 496 mm (say 500 mm) = 2500 mm

Floor Framing – Bearer Design Example AS 1684 Span Tables Floor Framing – Bearer Design Example Inputs required Wind Classification = N2 Stress Grade = F17 Floor Load Width (FLW) at A = 900 mm Roof Load Width (RLW) = 2500 mm Single or Continuous Span = Continuous Roof Mass (Sheet or Tile) = Steel Sheet (20 kg/m2) Bearer Span = 1800 mm

2 x 90 x 35mm F17 members joined together are adequate Floor Framing – Bearer Size 2006 Use 1200mm table Use 4500mm Simplify table 2 x 90 x 35mm F17 members joined together are adequate Inputs required Wind Classification = N2 Stress Grade = F17 Floor Load Width (FLW) at A = 900 mm Roof Mass (Sheet or Tile) = Steel Sheet (20 kg/m2) Single or Continuous Span = Continuous Roof Load Width (RLW) = 2500 mm Bearer Span = 1800mm

Floor Joist Design Example AS 1684 Span Tables Floor Joist Design Example Inputs required Wind Classification = N2 Stress Grade = F17 Roof Load Width (RLW) = 0 mm (just supporting floor loads) Single or Continuous Span = Continuous (max 1800) Roof Type = Steel Sheet (20 kg/m2) Joist Spacing = 450 mm

90 x 35mm F17 floor joists at 450mm crs Floor Framing – Floor Joist Design Example 2006 Simplify table 90 x 35mm F17 floor joists at 450mm crs are adequate Inputs required Wind Classification = N2 Stress Grade = F17 Joist Spacing = 450 mm Roof Type = Steel Sheet (20 kg/m2) Single or Continuous Span = Continuous (max 1800) Roof Load Width (RLW) = 0 mm Joist span = 1800mm At least 1800mm

Further Information Visit www.WoodSolutions.com.au For more than three thousand pages of information, inspiration and technical publications on everything about timber in the built environment. WoodSolutions is an initiative of Forest & Wood Products Australia.