Wall Materials and Construction

1. Removal of Restrictions in Choices of Wall Materials and Construction

   Shearwalls no longer implements literal interpretations of SDPWS tables which limited blocking, fastener selections, and stud spacing to those listed in those tables.

   These changes avoid unnecessary penalties for unblocked/blocked of combinations of sheathing capacity on either side of wall and lower maximum aspect ratios for short segments on unblocked walls. This became more necessary due to the addition of the blocked/unblocked sheathing combination rule with SDPWS 2021.

   These changes also simplify the user interface and eliminate many cases where materials seemingly inexplicably are not available.

   1. General Principles

      The program now allows more practical selections of materials than those explicitly given in Tables 4.3A for plywood siding, 4.3C for gypsum-based materials, and 4.3.5.3 for the wood structural panel unblocked factor.

      If no design capacity or adjustment factor is available in the table for that selection, it goes to the value for the next smallest size, longer fastener or stud spacing, or unblocked rather than blocked. Materials are excluded only if there is no design capacity or factor for a weaker selection, for example of a value is given only for blocked but not for unblocked.

      1. Restrictions based on Blocking for Gypsum-based Materials

         When "unblocked" appears in tables 4.3C for gypsum-based materials, for sizes and spacings that do not have a blocked entry in the table, it will now be interpreted as "this value is for when it is either unblocked or has this size/spacing, or both"

         This allows you to select "blocked" for the purpose of blocking both sides of the shear wall for the sheathing combination rules, but to use the only shear capacity listed for the selected combination of nailing and stud spacing.

      2. Restrictions based on Edge Spacing for Gypsum-based Materials

         The edge spacing values associated with unblocked walls in Table 4.3C will now be interpreted as "this value is for when it is unblocked and has no more than this spacing, rather than that precise spacing.

   2. Gypsum-based Materials (Table 4.3C)
      1. ½" 1-ply Gypsum wallboard, nailed.

         The program did not include 24" stud spacing if blocking is selected. It now allows 24" spacing and if blocked use the same capacity as unblocked.

      2. ½" 1-ply Gypsum wallboard, screws.

         Previously, only 8" edge screw spacing is allowed for unblocked walls. Now, 4, 6, or 8" spacing can to be unblocked, and the program uses the capacity for 8" unblocked.

         The 16" field screw spacing for or 4" edge spacing was available for both blocked and unblocked shear walls. It is now available only for blocked shear walls.

         Previously if 6" or 8" edge spacing is selected with 12" field spacing, then you select 4" edge, the field spacing goes to unknown. It now remains as 12"

      3. ½" x 2’ Gypsum sheathing board

         Previously blocking is unselected and disabled. It is now enabled and the capacity for unblocked used if it is selected.

      4. ½" x 4’ Gypsum sheathing board

         Previously the program allowed only 4" edge nail spacing for blocked and 7" for unblocked. It now allows 4 and 7" for both. For unblocked walls with 4" it uses the 7" capacity and for blocked with 7" it uses the unblocked 7" capacity.

      5. 5/8" x 4’ Gypsum sheathing board

         Previously the program allowed choices of unknown, 4" and 7" for edge spacing; it now just allows 4"

      6. Lath and plaster

         Previously only unblocked was allowed, now both blocked and unblocked are possible.

         Although blocking doesn't seem relevant to lath and plaster materials, this choice is provided because of the Note 1 in the Maximum Aspect Ratio table 4.3.3.referring to blocked vs. unblocked lath and plaster, and in case you want the program output to accurately indicate the wall construction for other reasons.

   3. Wood Structural Panels (Table 4.3A)
      1. Structural I and Structural Sheathing

         Previously the program interpreted Table 4.3.5.3 literally and did not allow unblocked shear walls to have less than 6" nail spacing because only values for 6" were listed in the table, and there is no apparent other reason to include these values in the table. However, it is now apparent that the values are listed to show that the associated factors apply to walls with 6" edge spacing, and that unblocked walls with lesser nail spacing can use these values.

         Depending on the sequence of operations the program disabled and checked blocking for edge spacings less than 6, or limited the list of edge spacings the single value of "6" when the wall was unblocked. It now always enables the blocking input regardless of the nail spacing and includes all nail spacings when blocking is checked. .

         Design for unblocked shear walls with spacing less than 6" uses the shear wall strength for 6" spacing, as per SDPWS 4.3.5.3

      2. Plywood siding

         Plywood siding was indicated as unblocked in the table, but it is customary to place blocking at all seams of plywood siding installations. The program now allows both blocked and unblocked plywood siding, defaulting to blocked, but uses the "unblocked" capacity from Table 4.3A.

2. Staggered Joint Gypsum Lath and Plaster

   The gypsum lath and plaster materials for for staggered lath joints was not in the program despite being listed in shear capacity Table 4.3C. Non-staggered lath and plaster is much weaker, so it was decided to add this material.

   1. Input

      The existing checkbox that says OSB for wood structural panels has been changed to Staggered when Gypsum Lath & Plaster is selected as the material type.

   2. Design

      The shear capacity design values of 128.6 for seismic and 180 for wind design are used.

   3. Output

      In the Sheathing Materials table, in the Material column, the designation Gyp lath&pl stg is shown.

3. Wall Material Nomenclature
   1. Lumber Sheathing vs. Lumber Siding

      In SDPWS Table 4.3D, the word "Sheathing" was removed from the name of all four orientations of lumber sheathing, replacing it with long names e.g. Single-Layer Horizontally- Sheathed Lumber. Noting that the word Siding was retained in the name Vertical Board Siding, it was decided to change the name of this material in the program to Lumber Siding.

      1. Input

         In Wall Input vIew, the selection Lumber sheathing has changed to Lumber siding.

      2. Output

         In the Sheathing Materials table the selection Lumber sheathing has changed to Lumber siding.

         In the legend to this table, the possibility of lumber planks rather than panels and the definition of Dbl (double diagonal) have been added.

      3. Elevation View

         In the materials specification in Elevation view, it used to just say "lumber sheathing" without giving the orientation. Now the following is output:

         horizontal lumber

         diagonal lumber

         dbl. diagonal lumber

         vertical lumber siding

   2. Gypsum Lath and Plaster

      In SDPWS Table 4.3C, the name of the material Gypsum lath was changed to Gypsum lath and plaster.

      1. Input

         In Wall Input vIew, the selection Gypsum lath has changed to Gyp. lath & plaster.

      2. Output

         In the Sheathing Materials table Gypsum lath has changed to Gyp lath/plaster.

      3. Elevation View

         In the materials specification in Elevation view, Gypsum lath has changed to gypsum lath & plaster.

   3. 2-ply Wallboard in Sheathing Materials Table

      2-ply gypsum wallboard was listed as a separate material from gypsum wallboard in the Sheathing Materials table and showed show a dash in the "ply" column, which ordinarily shows the number of plywood plies. Now a single name is used for gypsum wallboard and the 1 or 2 plies are shown in the plies column.

      1. Material Name

         In the Material column, the names Gyp WB 1-ply and Gyp WB 2-ply have been changed to Gyp. wallboard.

      2. Legend

         The definition of ply in the legend has been altered to include wallboard plies.

   4. Material Name Review and Changes

      The material designations shown in the Wall Input view drop down list, the Material column of the Sheathing Materials table in the Design Results, and the materials specification in Elevation View, were reviewed and modified.

      Previously Elevation view shows the same name as the wall input; now different names are used. The table below shows the changes.