Wood-Framed, Exterior Walls in Type III Construction with Engineered Wood Product Floor Framing Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board.
Course Description With the trend toward increased density, more designers are choosing Type III Construction in order to achieve greater heights and areas for their mid-rise wood-framed projects. This presentation will review 2015 IBC provisions for wood-framed exterior walls in Type III buildings as compared to Type V. Discussion will include how to maintain the intent of the code at the wall-to-floor intersections in scenarios that include wood-framed walls and engineered wood floors. Details illustrating the importance of correct rim specification when using platform framing and for semi-ballooned framed walls will also be provided.
Objectives 1. 2016 CBC provision differences between Type V and Type III construction. 2. Definition of fire-retardant-treated (FRT) wood, what materials can be treated, and reductions to design properties due to treatment. 3. Required fire-resistance ratings and maintaining those ratings at the wall to floor intersection. 4. Structural significance of proper rim specification with platform framing and detailing for semi-ballooned framed walls.
Architectural Details Structural Details
Use and Occupancy Classifications Residential Group R CBC Section 310 R1 R2 R3 R4
Type of Construction Type IV Fire Resistance Requirements Type I & II Size of Building TYPE V TYPE IV TYPE III TYPE II TYPE I Type of Construction Fire Resistance Type III Type V
Type Of Construction 2016 CBC Chapter 5, General Building Heights and Areas Section 504 - Height
Type Of Construction 2016 CBC Chapter 5, General Building Heights and Areas Section 504 - Stories Check Local Code Amendments City of Seattle allows 5 stories for Type V
Type Of Construction 2016 CBC Chapter 5, General Building Heights and Areas Section 504 - Area
Some exceptions Section 505.2 Mezzanines (no. of stories) Part of story below Shall not exceed 1/3 the floor area it is occupying Section 506.3 Frontage Increase (allowable area) More area permitted when access to public way 25% of building perimeter on public way Public way or open space at least 20 ft wide Section 510.5 Group R-1 and R-2 buildings of Type III A construction Increase to 6 stories with increase in fire protection
Materials Allowed for Types of Construction Type V Section 602.5 Any material permitted by code Most common for EWP Type III Section 602.3 Non-combustible exterior walls or Fire-retardant treated (FRT) wood allowed Interior building elements any material permitted by code Check Local Code Amendments
FRT Wood 3 Pathways to FRTW 1. CBC 2303.2.1 Pressure Process 2. CBC 2303.2.2 Other means during manufacture. The use of paints, coatings, stains or other surface treatments are not an approved method of protection as required in this section. 3. CBC Section 104.11 Alternative materials, design, and methods
FRT Wood Testing Flame Spread index of 25 or less (10 min) PLUS Extended ATSM E 84 (30 min) No evidence of significant progressive combustion Flame front shall not progress more than 10.5 ft Class A Flame Spread FRT Strength Adjustments Factors Wood Structural Panels Lumber Labeled
FRT Wood Evaluation Reports for FRT Chemicals Lumber Plywood Species Strength Reductions Corrosion Fastener Reductions
FRT Wood Platform Framing Challenge: Most SCL/GLB: not evaluated after FRT Dimensional changes SCL/GLB not warranted after pressure treatment Check with SCL/GLB manufacturer
Fire-Resistance Ratings for Building
Fire-Resistance Ratings for Building
Fire-Resistance Rated Assemblies CBC Section 703.3 Methods for determining fire resistance. Established by 1. Designs per approved sources 2. Prescriptive per Section 721 3. Calculated per Section 722 4. Engineering analysis based on ASTM E 119 or UL 263 5. Alternative means per Section 104.11 6. Certified Designs
Fire-Resistance Rated Assemblies Resources: International Building Code Intertek Underwriters Laboratories Gypsum Association Manufacturer s literature/code evaluation reports American Wood Council (DCA3) APA (D350A)
Fire-Resistance Rated Assemblies What are the requirements when the floor framing intersects the exterior wall? 2 hr FRT 1 hr 1 hr
Semi-Ballooned Framed Walls Things to consider Hangers Taller Studs Scheduling trades Design considerations Connections Eccentricity Not preferred
Platform Framed Walls Things to consider Preferred Eliminate Hangers Consistent Stud Heights
Platform Framed Walls Section 705 Exterior Walls 705.6 Structural stability. Band joist to be of fire-resistant construction Equivalent fire resistance to the wall Floor joists do not require fire-resistance equal to the wall See Table 601 Rating to Rim = ceiling rating + direct applied protection
Platform Framed Walls Type IIIA Wall - 2-hr Floor - 1-hr Additional 1-hr protection required for rim to total 2-hr rating Type IIIB Wall 2 hr Floor 0-hr Direct applied 2-hr protection required
Platform Framed Walls APA wall details D350A Ceiling Membrane + Direct Applied Protection Rim Board Protection
Platform Framed Walls Interek Listing 4. Rim Board Protection: Direct-applied protection listed in table, items A-E.
FRT Wood Is rim part of the wall framing? Does rim need to be FRT wood?
Rim Specification Critical Structural Component Transfer vertical loads Transfer lateral loads Compatible with I-Joists Same depth as I-joist or slightly greater Maintain depth compatibility CBC Section 2303.1.13 Conform to ANSI/APA PRR 410 or ASTM D 7672 Depth compatibility
Framing Details Options? Wide rim with joist hangers Check with EWP manufacturer s for proprietary solutions AC124 Acceptance Criteria for Rim Board Products Section 7.0 Factory-Applied Fire-Retardant Overlaid or Coated Rim Board for Interior Applications
Review Differences between Type V and Type III construction FRTW or equivalent at exterior walls 2-hr fire-resistance rated walls FRT wood Dimension Lumber or Plywood have been evaluated Class A Flame Spread FRT Fire-resistance ratings Type III exterior rim 2-hr fire-resistance rating Total rating = ceiling protection + rim protection 2 layer ceiling for EWP joists Details Platform framing proper rim specification Semi-ballooned framed walls - hangers
Questions? This concludes the American Institute of Architects Continuing Education System Program Renee Strand, P.E Weyerhaeuser Renee.strand@weyerhaeuser.com