Home Building – House Frame Work, Part 2

INTRODUCTION

• This article is the second of two about the fundamental materials and methods of house frame work in building a home 

HOUSE FRAME WORK

• Smoke-stopping
  • Shall be 
    • At fireblocked abuts to habitable space, e.g., stringer head,
    • At firestopped abuts to sleeping areas and hallway passages, e.g., through-penetrations in the field, such as through-plate electrical cables to a bedroom or water supply tubing in a stairway or hallway wall
    • Of not less than the L-rated materials conforming to not less than ANSI/UL 1479 (a/k/a/ American National Standards Institute/Underwriters Laboratories, “Fire Tests of Through-Penetration Firestops, 1994") 
• Dimensioned, or hand-framed, lumber shall be specified as to deflection limit(s) and all other relevant performance metrics at not less than such metrics for engineered lumber that may be applied in lieu 
• For hand-framed structure, the span table to follow shall be definitive at minimum as to a member's structure 

Comment:  The Span Table – Hand-Framing grew out of this designer’s frustration with contemporary tables of clearspans.  This custom home designers standard approach to floor truss deflection limits is L/480 overall, except in applications below masonry floors – ceramic where it’s L/600 (personally-assigned limit) and for natural, or stone, tile where it’s L/720 (reference: MIA, a/k/a Marble Institute of America).  

     You see, nowadays, every dimensioned lumber span table that the author’s laid eyes on tops out at L/360.  What’s the point?

     So the old geezer fetched here and there, and, with Dr. Frank Woeste’s absolutely vital assistance, this old boy found what he was looking for – a span table for dimensioned lumber at L/480 (with the added attraction that the simple math to get there could be applied to any load scenario). 

Span Table - Hand-Framing

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Key to abbreviations: CLG=CeiLinG; DL=Dead Load; EQV = Equivalent; FLR=Floor; JST = JoiST; L = Length; LL = Live Load; MAX = MAXimum; MIN = MINimum; NGT = Not Greater Than; NLT = Not Less Than; OA = OverAll; OC = On Center; RFR=RaFteR; SYP = Southern Yellow Pine; WL = WaLl. 

Comment:  The effect of this table - along with Part 1 prescriptions to delimit span tables generally - makes open web floor truss manufacturers happy, happy, happy.  Same goes more importantly, for the future residents who’ll walk on those floors every day forever after.  Whichever - hand- or truss-frame-  these leveled performance metrics will help level the floor. 

• For roof framing and floor framing structural metrics, the following shall be definitive at the minimum
  • Floor construction 
    • Shall generally be not less than equivalent L/480 at not less than 40 pounds live load and 15 pounds dead load except
      • Below finish masonry, shall be not less than L/600 at not less than 40 pounds live load and 15 pounds dead load
    • Shall apply 2 linear inches x 6 linear inches strongbacks
    • At mid-spans
    • Fastening to web member and bottom chords
    • Scabbing at right angles for not in-line situations
    • Shall involve contractor approval of truss shop drawings prior to manufacture
  • For roof construction
    • Not less than L/240
      • At not less than total load = 40 pounds per square foot
        • 30 pounds per square foot live load
        • 10 pounds per square foot dead load
        • Duration factor = 1.15
    • Plus all environmental loads
    • Plus roof materials total load
    • Shall involve contractor approval of truss shop drawings prior to manufacture 

Comment:  The engineered lumber guidelines to follow are suggestive of performance aspects to consider, notwithstanding requisite engineering latitude. That is, this should give you something to learn about, to talk about, maybe even in which to participate. 

• Glu-Lam beams (Dry adhesive)
  • Fb = 2400
  • Not less than L/480
• Parallel Strand Lumber (a/k/a PSL) 
  • Fb = 2900
  • E = 2.0
  • Fv = 290
• Laminated Veneer Lumber (a/k/a LVL) 
  • Fb = 2600
  • E = 1.8
  • Fv = 285
• Noting well that in all applications
  • Prohibited materials include
    • Wood composite I-beams
    • Rim boards not engineered
    • Oriented strand board and
    • All other oriented particle-component materials shall be prohibited materials
• Wood materials in floor and roof framing shall be of not less than #2 grade
• Members shall be spaced at not greater than 16 linear inches on center

• Framing structure shall be supported by framing structure, and not with toe-nails 

Comment:  This note is specifically aimed at ends of members to hip ridges and all forms of valley, but could be just as pointed to some deck joists we’ve seen fastened to “ledgers." 

Comment:  If you can only toe-nail one member to another, get out your Simpson Strong-Tie “Wood Construction Connectors" catalogue, and find something definite and necessary to your purpose. 

• Framing structure shall be supported by framing structure, and not air 

Comment:  This note is specifically aimed at studs and posts set on bottom, or sole, plates without full-depth and -width solid blocking to sills, girders and the like.  This framing failure is a whole lot easier to commit than you might think.   

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