• Wood Frame Construction Manual 2015 Pdf

The majority of changes to the 2018 WFCM reflect increased C&C wind pressures in ASCE/SEI 7-16. 0-70 psf ground snow loads.

90-195 mph 3-second gust basic wind speeds for risk category II buildings. Seismic Design Categories A-D The WFCM includes design and construction provisions for connections, wall systems, floor systems, and roof systems. A range of structural elements is covered, including sawn lumber, structural glued laminated timber, wood structural panel sheathing, I-joists, and trusses. Comparison of C&C roof coefficients a (suction). Comparison of C&C roof overhang coefficients (suction). Figure 3 provides an overview of the various roof zones as defined in ASCE/SEI 7-16 for a gable roof with roof slopes between 7 and 45 degrees.

Tables 1a and 1b also show the roof coefficients as implemented for 2018 WFCM chapters 2 and 3. WFCM Chapter 2 uses the maximum magnitude suction loads for roof slopes between 7 and 45 degrees in Roof Zones 1, 2, and 3. WFCM Chapter 3 further simplifies the roof loading requirements by combining Roof Zones 2 and 3 into an end zone and reducing the magnitude of Zone 3 loads by limiting rake overhangs. As a result of these simplifications, the effective uplift pressures on critical roof edge and overhang zones is limited to an 11% increase in WFCM Chapter 3 requirements as shown in Tables 1a and 1b (e.g., -4.1 coefficient under ASCE 7-16 versus -3.7 coefficient under ASCE 7-10).

This results in a smaller increase in uplift load requirements between editions of the WFCM than the actual percent increase in design pressures between ASCE/SEI 7-10 and ASCE/SEI 7-16. Overview of various gable roof zones as defined in ASCE/SEI 7-16. Roof Rake Overhangs Rake overhang provisions were revised to clarify terminology and limit rake overhang lookout blocks to 9 inches (previously limited to 12 inches) based on increased wind pressures ( Figure 4a).

Rake overhang outlooker provisions were expanded to tabulate requirements for overhang spans of 12, 16 and 19.2 inches in addition to 24 inches previously tabulated ( Figure 4b). The smaller span cases were added to address increased wind pressures and remove conservatism associated with tabulated requirements based only on assumed 24-inch overhang span. Rake overhang outlooker and lookout block details (excerpted from 2018 WFCM). Changes to Fastener Design Wind uplift related changes include new fastener withdrawal and new fastener head pull-through design provisions. Roof Sheathing Ring Shank Nails Roof Sheathing Ring Shank (RSRS) nails were recently added to ASTM F 1667 Standard Specification for Driven Fasteners: Nails, Spikes, and Staples. Design provisions for RSRS nails have been added to the 2018 NDS and 2018 WFCM. RSRS nails, which have larger withdrawal design values than smooth shank nails of equal length and diameter, provide additional options for efficient attachment of wood structural panel roof sheathing.

In many cases, specification of RSRS nails will produce a reduced roof sheathing attachment schedule than permissible by use of smooth shank nails and enable the use of a single minimum fastener schedule for roof perimeter edge zones and interior zones. Recognition of higher withdrawal strength is based on the presence of 1½-inch length of standardized ring deformations on the nail. Fastener Head Pull-through Provisions Fastener head pull-through design in accordance with NDS 2018 is incorporated into sheathing attachment requirements for resistance to wind uplift/suction forces. For the design of roof sheathing fastening to resist wind uplift, the lesser of the head pull-through design value or the fastener withdrawal design value from wood is used to establish the “fastener uplift capacity,” as shown in Figure 5. Excerpt from 2018 WFCM Table 3.10 showing fastener uplift capacity controlled either by nail withdrawal capacity or head pull-through. Example Compare fastener uplift capacity of 8d Common and RSRS-03 nails as shown in Figure 5.

Fastener uplift capacity is the lesser of withdrawal and head pull through. Assume 180 mph Exposure B wind loads, 19⁄32-inch WSP sheathing, framing specific gravity (G) = 0.49 or higher, and rafter spacing = 24 inches.

Wood Frame Construction Manual 2015 Pdf

Using 2018 WFCM Table 3.10, the required nailing pattern (i.e., panel edge/panel field) at roof perimeter zones and interior zones is shown in Table 2. Comparison of RSRS-03 to 8d common nailing patterns for high wind.

A In this case, the RSRS nail provides nailing pattern options that reduce required nailing when compared to 8d common smooth shank nails. Shear Wall Assemblies Shear wall aspect ratio adjustments were revised to be consistent with the 2015 SDPWS. Shear walls using gypsum wallboard are subject to the following limits (underlines show clarifying text added to 2018 WFCM): Gypsum wallboard walls having aspect ratios exceeding 1.5:1 shall be blocked. Where shear walls are gypsum wallboard only, the maximum aspect ratio shall not exceed 2:1 in accordance with AWC/ANSI Special Design Provisions for Wind and Seismic (SDPWS) Table 4.3.4. Elevator mechanic test preparation study guide. Requirements for shear walls with blocked wood structural panel sheathing are now tabulated assuming a maximum shear wall segment aspect ratio for wind of 2:1 (previously 3.5:1).

However, the 2018 WFCM still allows aspect ratio increases up to 3.5:1 for walls with blocked WSP sheathing or structural fiberboard sheathing, provided the unit shear capacity and sheathing type adjustment factor are adjusted in accordance with 2015 SDPWS Section 4.3.3.4.1 Exception 1 for wood structural panel shear walls or Exception 2 for structural fiberboard shear walls. Applicability to Non-Residential Structures IBC 2309 allows for use of the WFCM for non-residential structures within its scoping limitations: (IBC) 2309.1 Wood Frame Construction Manual.

Structural design in accordance with the AWC WFCM shall be permitted for buildings assigned to Risk Category I or II subject to the limitations of Section 1.1.3 of the AWC WFCM and the load assumptions contained therein. Structural elements beyond these limitations shall be designed in accordance with accepted engineering practice. While WFCM provisions are intended primarily for detached one- and two-family dwellings due to the floor live load assumption associated with those occupancies, many of the WFCM provisions for specific geographic wind, seismic, and snow loads may be applicable for other buildings. For example, wind provisions for sizing of roof sheathing, wall sheathing, fastening schedules, uplift straps, shear anchorage, shear wall lengths, and wall studs for out of plane wind loads are included in the WFCM and are applicable for other use groups within the load limitations of the WFCM tables. Similarly, roof rafter size and spacing for heavy snow and shear wall lengths and anchorage for seismic are applicable within the load limitations of the WFCM tables. Examples of non-residential applications include single-story wood structures or top stories in mixed-use structures in Risk Categories I or II. Applications outside the scope of the WFCM tabulated requirements, such as the design of floor joists and supporting gravity elements for floor live loads greater than 40 psf are beyond the applicability of the WFCM and must be designed in accordance with accepted engineering practice.

This parallels the approach taken in IRC Section R301.1.3, which permits unconventional elements of one- and two-family dwellings to be designed per the IBC. More Details A section by section list of changes to the WFCM is available in the Appendix, following the article, in the pdf version,. Availability The 2018 WFCM is currently available in electronic format (PDF) only.

Once the WFCM Commentary is updated, printed copies will be available for purchase. Check the AWC website for status updates on the 2018 WFCM. Conclusion The 2018 WFCM represents the state-of-the-art for the design of wood members and connections. The 2018 WFCM updates pre-engineered design provisions based on loads from ASCE 7-16 and design requirements from the 2018 NDS and 2015 SDPWS.

Both the 2018 IRC and 2018 IBC reference the 2018 WFCM for the design of wood structures.▪ Watch for an upcoming article on navigating the new ASCE 7-16 and 2018 IRC requirements for determining components and cladding roof pressures.