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MDSS Medium Diaphragm Spline Strap


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The MDSS96 surface spline is 95 1/2" long, is attached with Strong-Drive® SDS Heavy-Duty Connector screws and is an ideal solution for CLT diaphragms. For CLT manufacturers, it reduces costs by eliminating or reducing time for milling at panel edges. And since our tabulated values are based on tests, not just calculations, Designers can value-engineer a solution using fewer screws than calculated solutions would allow.

Key Features

  • Pre-punched screw holes speed fastener installation
  • Tested loads allow for value-engineered solutions using fewer screws than calculated solutions would allow
  • Reduces or eliminates the need for edge-milling of CLT panels


  • 14 ga.


  • Galvanized (G90)


  • Use all specified fasteners/anchors

Related Literature

Load Tables

Allowable Shear Loads
Model No. Ga. CLT Layup Fasteners Fastener Spacing (in.) Allowable Shear Load per Fastener (lb./ft.)
Slip Modulus per Fastener (lb./in.)
MDSS96 14 3-Ply 1/4" x 3 1/2" SDS 8 1,010 960 16,875 16,875
6 1,345 960 16,875 16,875
4 2,015 1,440 16,875 16,875
5-Ply, 7-Ply 1/4" x 6" SDS 8 1,010 960 16,875 16,875
6 1,345 960 16,875 16,875
4 2,015 1,440 16,875 16,875
  1. Allowable loads have been increased for wind or seismic loading with no further increase allowed: reduce where other loads govern.
  2. Applicable adjustments shall be applied following the ANSI/AWC NDS-15 or NDS-18.
  3. Tabulated values are applicable for splines in the major and minor strength directions.
  4. Screws: 1/4" x 3 1/2" SDS = model SDS25312; 1/4" x 6" SDS = model SDS25600; 0.22" x 4" SDWS = model SDWS22400DB; 0.22" x 6" SDWS = model SDWS22600DB
  5. CLT panel minimum thickness is: 3-ply = 4.125"; 5-ply = 6.875"; 7-ply = 9.625"
  6. The component of diaphragm deflection due to fastener slip at panel-to-panel joints is calculated as,
    δf = CLen
    • C=(1/PL+1/Pw)/2
    • PL = Length of individual CLT Panel (ft.)
    • Pw = Width of individual CLT Panel (ft.)
    • L = Overall length of diaphragm (ft.)
    • en = Force per fastener [lb]/Slip modulus [lb/in.]

(Reference — Applied Technology Council. 1981. Guidelines for the design of horizontal wood diaphragms. Redwood City, CA.)

For additional information on slip modulus, see:

  1. American Wood Council. 2018. ANSI/AWC National Design Specification for Wood Construction, NDS®, Section 11.3.6. AWC, Leesburg, VA.
  2. Zhan, J.J. 1991. Design equation for multiple-fastener wood connections. US Forest Service, Forest Products Laboratory, Madison, WI. 9 pp.0

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