1. Wood structures Topic 3 Floor Framing
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Wood Structures
Floor Framing
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2. Wood structures Topic 3
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Floor Framing
Floor framing in wood platform frame houses must be designed and constructed to:
Transfer loads to the buildings structural elements.
Resist deflection and excessive vibration.
Provide an acceptable surface for finishing flooring materials.
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3. Floor Framing Introduction
Wood structures Topic 3
21/09/2018
Floor Framing Introduction
Loads from other floors and the roof are often transferred through the floor system to the foundation.
Also they support their own weight and live loads from occupants, appliances and furniture.
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4. Pay Attention Wood structures Topic 3 21/09/2018 9/21/2018 BLDG 1101
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5. Transferring Loads Wood structures Topic 3 21/09/2018 9/21/2018
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6. Load transfers down rafter
Wood structures Topic 3
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Transferring Loads
Load on roof
Load transfers down rafter
Through top plates
Down studs
Through floor structure
Down through foundation
Through footing
Onto soil below
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7. Watch the load Wood structures Topic 3 21/09/2018 9/21/2018 BLDG 1101
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8. Floor framing introduction
Wood structures Topic 3
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Floor framing introduction
Beams, joists and subflooring materials need to be selected based on strength and stiffness.
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9. Wood structures Topic 3
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Introduction
The size of the component is governed by the loads and the strength of the material used.
Stiffness prevent excessive deflection and limit vibration and cracking of ceilings.
Characteristics of a floor system depend on a number of factors:
Wood species, grade, size of members, subfloor thickness and means of fastening to joists, and extent of load sharing between adjacent members.
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10. Wood structures Topic 3
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Introduction
Wood platform houses are designed and constructed under GBJ 5 Chapter 9 (Part 9) or based on engineering calculations.
For floor framing, the code applies where joists are spaced not more than 600 mm (or 610 mm), floor area of each storey does not exceed 600 sq. metres, and live loads for floors do not exceed 2.5 kPa.
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11. Introduction grade species loading condition span spacing
Wood structures Topic 3
21/09/2018
Introduction
Size of floor joists are determined in the code based on
grade species
loading condition
span
spacing
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12. Introduction Topics covered
Wood structures Topic 3
21/09/2018
Introduction
Topics covered
Floor assemblage, floor system anchorage, moisture protection, beams, sill,
Joists
Selection, support, and connecting
Floor openings, interior wall support, cantilevers
Subfloors
Notching and drilling
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13. Floor Assemblage Typically consists of the following components.
Wood structures Topic 3
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Floor Assemblage
Typically consists of the following components.
Sill plate of treated dimension lumber anchored with bolts to the top of the foundation walls with gasket and caulking to seal joint
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14. Wood structures Topic 3
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Floor Assemblage
Joists of dimension lumber or engineered wood products, spanning the building width and bearing on sill plates and beams.
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15. Wood structures Topic 3
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Floor Assemblage
Beams (Girder) of built-up dimension lumber or engineered wood products, supporting joists at intermediate points between foundation walls.
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16. Wood structures Topic 3
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Floor Assemblage
Header joists of dimension lumber or engineered wood product, securing joist ends and other end of joist bearing on sill plates.
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17. Wood structures Topic 3
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Floor Assemblage
Strapping, cross-bridging or blocking of dimension lumber, tying joist together between points of bearing.
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18. Wood structures Topic 3
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Floor Assemblage
Subfloor of structural wood-based panels, laid in an alternating pattern with lengths at right angle to joists and width joints over joists.
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19. Header, rim or band joist
Wood structures Topic 3
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Sill plate
Header, rim or band joist
Framed opening
Girder or beam
Subfloor
Column and footing
Joist
Poured concrete foundation wall
Blocking
Footing
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20. Rough Framing Basics
Rough Framing refers to the building of the wood structural elements
Rough Framing is not visible when the project is complete
Rough Framing requires accuracy in installation because finishes are not always able to hide errors in:
Layout
Level (horizontal) and Plumbness (Vertical) of framed members (floors, walls, ceilings, and roofs)
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21. Floor System Anchorage
Begins on top of the foundation wall with the sill plate. Usually a 2 x 4 or 2 x 6 anchored to the foundation wall with anchor bolts
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22. Floor System Anchorage
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23. The sill plate should be pressure treated
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24. Floor System Anchorage
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25. Floor System Anchorage
Floor systems must be anchored to the foundation to resist uplift and lateral forces from wind and earthquakes.
Ground floor joists and the entire floor system are connected to the sill plates with anchor bolts embedded in the foundation.
This provides a strong connection, so important to earthquake zones.
Sill plates also support joists and headers and transfer floor loads to foundation walls.
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26. Floor framing
Sill plates must be pressure treated if in direct contact with concrete foundation wall.
Anchor bolts are:
minimum 12.5 mm in diameter
Maximum spacing, 2400 mm O.C.
Imbedded minimum 100 mm into foundation
Designed to not pull out of wall when tightened
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27. Note: Washer
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31. Moisture Protection
The code requires that the junction between the foundation and the sill plate be sealed, as this is a potential source of air leakage into the building, by caulking with a sealant material.
In addition to caulking, a gasket is sometimes used to facilitate sealing and resist moisture transfer between foundation and sill plate.
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32. Moisture Protection
To reduce the possibilities of water penetration, the Code requires a minimum clearance between the ground floor level and the finished grade of no less than 300 mm.
In insect prone areas, the clearance should be no less than 450 mm and the ground should be covered with a moisture barrier.
Use wood that is treated with wood preservatives to prevent the risk of insect infestation.
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33. Moisture Protection
The Code requires that any framing members less than 150 mm above finished ground level are either preservative treated or separated from the ground by a moisture barrier.
Treat preserved members with ends or holes exposed from sawing or drilling with at least two coats of preservative.
Use preservative treated wood that has significant risk of attack from insects, particularly termites.
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34. Beams
Floor beams are located between foundation walls and may also be supported on columns.
Today beams are generally made from:
Steel
Built up wood beams
Made from 3, 4, or 5 ply dimensional lumber nailed or bolted together.
Paralam beams (A manufactured wood fibre beam)
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35. Beams
Beams support floor joists and loads imposed by stories above the beam.
They transfer loads to the columns and/or foundation walls.
Beams must be securely anchored to the columns.
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36. Girders Heavy beams that support inner ends of floor joists
Size should be determined by the code tables or professional engineers
Applying glue between pieces makes the bond stronger
Ends supported by pocket formed in foundation wall or columns
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38. Installing Beams/Girders
Steel beams (girders) usually come in one piece.
Wood beams (girders) usually erected in sections.
Beams made from engineered lumber products.
Size of beams depends on; species, grades, spans and loads including number of stories.
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39. Beams/Girders
Columns and beams supporting the floor system should be located according to approved floor plans.
The following drawing shows the nailing pattern of built up wood beams.
The next slide also shows the assembly of the single pieces wood .
Note where the joints are located
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41. Built up Wood Beams
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42. If possible stager joints directly over columns
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43. Nailing of Built Up Wood Beams
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46. Beams
Beams can be fastened and placed in many different configurations
Design depends on issues such as
Ease of placement
Headroom requirements
Type of materials being used
Minimum Bearing 89 mm or 3 ½” (except as required in notes to Tables A - 8 to A – 11, OBC
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47. Beams
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48. Beams
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49. Steel Beam
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50. Laterally supported steel beams
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52. Joists/selection
Joists are made from either dimension lumber or engineered lumber.
According to the code, spacing between joists will not exceed 600 mm
The size of joists made from dimension lumber are determined from span tables in accordance with GBJ 5 requirements..
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53. Joists/selection
The minimum sizes for joists using dimension lumber depends on:
Species
Grade
Load requirements
Spans
Spacing
Allowable spans are measured between edges of supports.
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54. Joists/ load sharing
Load sharing involves fastening floor components together so the floor system acts as a unit.
Strapping in combination with bridging or solid blocking adds stiffness and reduces vibration.
It also resists any tendency for joist twisting.
Cross Bridging, Solid Bridging, and Strapping are forms of strengthening that meet the requirements of Floor Joist sizing tables A-1
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55. Load sharing
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56. Joists/ load sharing Other factors that help load sharing are:
Increase the thickness of the subfloor
Gluing the subfloor as well as nailing or screwing it to the joists.
Gluing and screwing also makes the floor more silent.
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57. Nailing and Securing of Joists
Joists can be strengthened by the use of Bridging.
Cross Bridging, Solid Bridging, and Strapping are forms of strengthening that meet the requirements of Floor Joist sizing tables A-1
Maximum spacing for rows of bridging is 2.1 m from supports or from other rows.
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58. Nailing and Securing of Joists
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59. Joists/ load sharing Strapping bridging and blocking
Strapping refers to full length pieces fastened to the underside of joists
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60. Joists/ load sharing
Cross bridging consists of pairs of diagonal braces crossing each other between joists.
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61. Joists/ load sharing
Solid blocking (bridging) consists of blocks (same dimension as joists) fitted between and at right angles to joists
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62. Floor joist/ support
Floor joists need at least 40 mm mm of end bearing.
Joists may be framed on top or wood beams or framed into their sides.
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63. Floor joist/ support
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64. Floor joist/ support
When framed into wood beams, joist must be supported by hangers, connectors or by ledgers properly nailed.
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65. Floor joist/ support
When framed into the sides of steel beams, joists are supported on either the bottom flange or a ledger bolted to the web. Joist are spliced on top of the beams.
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66. Floor joist/ support
Joists framed into the sides of a steel beam give it lateral support, as there is a tendency for steel beams to buckle sideways under heavy load.
Leave at least 12 mm between splice and top of beam to allow for shrinkage.
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67. Floor joist/ support
Joists on top of steel beams can provide lateral support with the use of flanges.
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68. Joists
Engineered wood I-joists are an alternative to dimension lumber.
A floor with wood I-joists is often referred to as a engineered floor system because it is designed using the manufacturer’s structural data and standard engineering calculations.
Support details, location, bracing and bridging details, point loads, dead loads, bearing lengths, connector hardware and details should all be included on drawings and engineering reports for these floor systems
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70. Floor joists/ connecting
The structural elements are primarily connected by nails.
It is good building practice to ensure that at least half the nail’s length penetrates the second member and that nails be staggered along the grain and kept well in from the edges to avoid spitting.
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71. The following table sets out the minimum nailing requirements for floor joists
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72. Engineered floor system
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