Chapter 5 Wood Light Frame Construction Fundamentals of Building Construction Materials Methods 5th Edition Copyright 2009 J Iano All rights reserved Light Wood Framing Advantages Flexible Easily constructed Economical Disadvantages Burns rapidly Decays if exposed to moisture Changes volume with moisture changes Framing unattractive must be covered Balloon Frame North American invention 1833 Heavy Timber Large timbers complicated joinery skilled craftsman Light wood framing smaller dimension wood members simpler nailed connections requiring less skilled builders Necessary technologies water or steam powered saw mills machine made nails railroad transportation Balloon Frame Wall studs are continuous the full height of the frame Balloon Frame All Light Wood Framing Full Length Studs Cost Less than Timber Disadvantages Full length studs difficult to handle Hang 2nd floor platform No firestop Unbroken Studs Firestop Wood Ribbon Sills Platform Frame Post WWI variation on the balloon frame Relies on shorter length framing members that are easier to produce handle and erect Platform frame Single story height wall studs span only between floor platforms Platform Frame Advantages Short easily handled lumber Made entirely of 2 lumber Automatic fire stop Working platforms Nail Connections Disadvantage Vertical shrinkage thick layer of wood which wood grain runs horizontally Studs Studs Sole plates Platform Frame sequence Construction Concept 1 2 3 foundation first floor platform first floor walls Platform Frame sequence Construction Concept 1 2 3 foundation first floor platform first floor walls 4 5 6 second floor platform second floor walls roof ceiling Platform Frame Parallel nominal 2inch members spaced at 16 or 24 Floor ceiling joists Wall studs Roof rafters Plywood or OSB structural panels Subflooring Wall and roof sheathing FOUNDATIONS FOR LIGHT FRAME STRUCTURES Building Sequence Building Layout Locating Footings Prior to Excavation Batter Board Typical Basement Foundation Excavation to at least below the frost line Cast in place concrete strip footing Cast in place concrete foundation wall 8 to 12 thick 8 to 10 tall Typical Foundation Anchor bolts cast into top of foundation wall Steel reinforcing top and bottom of foundation wall Dampproofing or waterproofing on outside of foundation wall Crushed stone and perforated perimeter drain piping Backfill after floor platform is erected to brace walls Slab on grade may be delayed until after structure is closed in Foundation Insulation Insulate the Crawl Space Insulate the Exterior of the Wall Insulation exposed to the elements Insulate the Interior of the Wall Attach to Platform or on Ground Vapor Barrier Space condensation considerations Insulation within the Wall CMU Foundation Insulation Exterior rigid foam insulation exposed insulation but be covered with a protective finish Interior glass fiber batt insulation Rim joist insulation Cast in place concrete foundation wall with anchor bolts protruding Note pockets in far side of concrete wall for setting of floor beams Expanded polystyrene rigid foam foundation insulation BUILDING THE FRAME Erecting the Platform Frame Considerations Attachment to the Foundation Floor Framing Sheathing Ground Floor Platform Sill plates are anchored to foundation Girders are placed Floor joists are laid Subflooring is applied Attachment to the Foundation Sill Material Termite Shield Sill Attachment Decay Resistant Anchor Bolts Expansion Bolts Add l for Wind Quake Set to Line Elevation Floor Framing Material 2 Material larger sizes optional Trusses I Beams Wood Metal or Combination Floor framing with 2x12 solid member joists Floor Framing Spacing Splicing Spacing Factors Influencing Joist Spacing Designation Inches o c on center Floor Loading Minimums in Code Span Length Strength of Joist Material Used Sheathing strength size Typical 16 oc Other Typ Options 12 or 24 Splicing a In Line w metal strap or wood b Lapped Floor Framing Bridging Anchorage Bridging Joist Hanger Metal Sized to Joist Purpose Anchorage Support Material Wood or Metal Purpose Improve Rigidity Hold Joist Straight Distribute Loads Code requires for joists 2x12 Floor Framing Sheathing Materials Plywood or OSB Installation Perpendicular to the Floor Joist Nails Screws Glue Staggered End Joints Ground Floor Walls Sections of wall are assembled lying down on the floor platform and then are tilted into place Temporary bracing holds walls in proper alignment Wall sheathing may be applied before the walls are stood up or later as shown here after the frame is fully erected Framing Terminology Top Plate Often Doubled Stud Header Sheathing Sole Plate Top Plate Double Top Plate Joist Support Tie Framing Together Double Top Plate Header Supports Double Header Corner Framing Sole Plate Anchorage Ground Floor Walls Bottom plates are nailed to the floor platform Top plates are doubled to provide adequate strength to carry the joists or rafters that will be placed above The upper top plate also overlaps and ties together adjacent sections of wall that were assembled and tilted up separately Studs are continuous between top and bottom plates except at door and window openings Walls are constructed in sections lying down on the floor platform and then tilted up into position Temporary bracing is used to hold the wall in place Adjustable bowed springboards allow more precise alignment of the walls Window rough opening The header is supported by two supporting jack studs at either end The rough sill and head are also doubled Note the OSB sheathing higher on the wall and preservative treated plywood below for greater protection from moisture damage due to differences in finish and grade conditions on the exterior side Headers Sizing Factors Load Span Material Code Materials 2 Laminated Composite Metal A glu lam beam spans a garage door rough opening Note the temporary bracing supporting jack studs at each end of the beam and the top plate overlapping at the foremost corner so as to tie the two wall planes Shear Walls Steel strap seismic holddowns cast into the concrete foundation will be nailed to the wall after the sheathing is applied Shear Walls This light wood framed shear wall for a multistory residential building in a region of high seismic risk requires special attention to panel strength nailing patterns and transfer of loads across panel joints to provide the necessary resistant to lateral wind and seismic forces Wall Sheathing Materials Typically