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MTWS™ Mass Timber Washer Strap

Simpson Strong-Tie® tested and load-rated tension straps and fasteners are designed to minimize cost and maximize speed and precision — while providing the strength, versatility and reliability you depend on. The MTWS48 strap utilizes MTW45-8 washers and Strong-Drive® SDCF Timber-CF (SDCF) fully-threaded countersunk-head screws. The combination provides a tension strap with high strength and stiffness that can be used in a variety of CLT diaphragm and wall applications. The MTWS48 is a 7-gauge high-capacity strap specifically designed to carry tension across a CLT floor or wall panel joint. The MTWS48 can also be used to attach CLT panels to steel attachment points when paired with a welded connection (designed by others).

Key Features

  • High capacity reduces the need for expensive shop-fabricated steel plates
  • Use of inclined SDCF screws and MTW45-8 washers reduces the number of fasteners needed to achieve the load
  • Strap can be used for either CLT panel-to-panel connection or CLT panel-to-steel connection


  • 7 gauge (ASTM A653 Grade 33)


  • Galvanized


  • Install optional fasteners in diamond holes to hold strap in desired location
  • Orient washers so the screws point away from the centerline of the strap and toward the end of the strap
  • Install inner fasteners first and work towards the ends of the strap
  • Reference engineering letter L-F-MTINSTALL for additional fastener installation information
  • Use all specified fasteners and washers


  • Multiple combinations of strap width and fastener length are available
  • Full straps may be used to connect CLT panels together
  • Full straps may be cut into half straps; these half straps may be used to connect CLT panels to steel attachment points (designed by others)

Related Literature

Product Information Table

Fastener Production Information and Stuff & Things
New products
Model No. Ga. W (in.) L (in.) Coating/Material Packaging Qty.
MTWS48-5.5 7 5 7/16 47 5/8 Zinc Galvanized, G90 1
MTWS48-8 7 8 1/16 47 5/8 Zinc Galvanized, G90 1

Load Tables

Allowable Tension Loads

Model No. Ga. Dimensions (in.) CLT Layup (min.) Fasteners (Total) Allowable Tension (lb.) (160)
MTWS48-5.5 7 5 7/16 47 5/8 Three-Ply (24) SDCF22512 11,160
MTWS48-8 8 1/16 (36) SDCF22512 16,740
MTWS48-5.5 5 7/16 Five-Ply (24) SDCF22858 18,655
MTWS48-8 8 1/16 (36) SDCF22858 27,600
  1. The allowable loads are based on the use of cross-laminated timber (CLT) grades E1-E5 and V1-V5 material conforming to APA PRG-320. The allowable shear load applies to CLT with specific gravity of 0.42 or better and MPP with equivalent specific gravity.
  2. Allowable loads have been increased for wind or seismic loading with no further increase allowed; reduce where other loads govern.
  3. When predrilling is used, predrill diameter is 3/16" maximum.
  4. Use all specified fasteners and washers. Use half of the required fasteners in each member being connected to achieve the listed loads.
  5. Tension loads apply for uplift when installed vertically.
  6. Fasteners: SDCF22512 and SDCF22858 = 0.315" OD by 5 1/2" long and 8 5/8" long Strong-Drive SDCF TIMBER-CF screw, respectively.
  7. Tabulated values are applicable for parallel and perpendicular to the outer layer of CLT.
  8. CLT panel thickness shall be adequate to accommodate full fastener length.

Code Reports & Compliance