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STHD Strap-Tie Holdown

Strap-Tie Holdowns

This product's information may differ depending on the category of use. You are currently viewing details related to Strap-Tie Holdowns. You can also view product information related to the category: Holdowns and Tension Ties for Cold-Formed Steel Construction

The STHD is an embedded strap-tie holdown offering high loads in both wood and cold-formed steel construction. When installed on the forms with the StrapMate® strap holder, the unique design delivers enhanced stability before and during the pour to help prevent both parallel and perpendicular movement. This results in accurate positioning of the strap and reduced possibility of spalling.

Key Features

  • The staggered nailing pattern helps to minimize splitting and allows for nailing to the edges of double 2x members
  • Strap nail slots are countersunk to provide a lower nail head profile when used with specified fasteners
  • The slots below the embedment line enable increased front-to-back concrete bond and help to reduce spalling

Material

  • 12 gauge

Finish

  • Galvanized

Installation

  • See General Notes for Holdowns and Tension Ties.
  • Use all specified fasteners; see General Notes.
  • Use tables for both standard concrete and post-tension slab installations.
  • Install before concrete pour with a StrapMate, or other holding device. Use of StrapMate (SM1) aids in keeping STHD plumb during installation.
  • Nail strap from the bottom up. Install strap plumb.
  • Strap may be bent one full cycle (bent horizontal 90° then bent vertical) to aid wall placement, but may cause spalling behind the strap. If the spall is 1" or less, measured from the embedment line to the bottom of the spall, full loads apply. STHD10 and STHD14 achieve full load for spalls less than 4". Any portion of the strap left exposed should be protected against corrosion.
  • Other than where noted in the two-pour detail, do not install where: (a) a horizontal cold joint exists within the embedment depth between the slab and foundation wall or footing beneath, unless provisions are made to transfer the load, or the slab is designed to resist the load imposed by the anchor; or (b) slabs are poured over concrete block foundation walls.
  • Additional studs attached to the shearwall studs or post may be required by the designer for wall sheathing nailing.
  • Wood shrinkage after strap installation across horizontal members may cause the strap to buckle outward.
  • For installations in severe corrosion environments, refer to General Corrosion Risks for additional considerations.
  • See installation illustrations in the image gallery for rebar information.

For Two-Pour Installation for Downturn Footings

  • For STHD10 installed through a 4"-thick slab, use the equivalent 8" stem wall loads of the LSTHD8
  • For STHD14 installed through a 4"-thick slab, use the equivalent 8" stem wall loads of the STHD10
  • For STHD14 installed through a 6"-thick slab, use the equivalent 8" stem wall loads of the LSTHD8

Related Literature

High Wind Guide
F-C-HWG23
A comprehensive guide to help designers select the most appropriate connections for high-wind regions.
Product Guide
Conectores para la construcción con madera 2021–2023
C-C-2021SP
El catálogo incluye información sobre nuevos productos, así como especificaciones e instrucciones de instalación aplicables para conectores estructurales de madera a madera y de madera a concreto.
Catalog
Wood Construction Connectors – Canadian Limit States Design
C-C-CAN2022
A complete product and application catalogue including load tables and installation information for wood-to-wood, wood-to-concrete and wood-to-masonry connectors.
Catalog
Connecteurs pour constructions en bois — Conception aux états limites canadiens
C-C-CAN2022CF
Un catalogue complet sur les produits et les applications, y compris de l’information sur l’installation et les tableaux de charge pour les connecteurs bois-à-bois, bois-à-béton et bois-à-maçonnerie.
Catalog
Wood Construction Connectors 2024-2025
C-C-2024
A catalog including new product information as well as any applicable specification and installation instructions for wood-to-wood and wood-to-concrete structural connectors.
Catalog
Connectors for Cold-Formed Steel Construction Catalog
C-CF-2023
A catalog for Connectors for Cold-Formed Steel Construction products and solutions.
Catalog
Installer's Pocket Guide
S-C-INSTALL22
A bilingual pocket installation guide for connectors.
Product Guide
Connector Solutions to Meet the Wall Bracing Requirements of the International Residential Code®
T-C-WALLBRACE23
A technical bulletin providing technical information about wall bracing methods and code sections that require connectors (e.g., holdowns or straps) and anchors.
Technical Bulletin
Connectors Installed on SCL Columns
T-C-SCLCLM23
A technical bulletin discussing the structural properties of the two different surface sides of SCL columns, with connector solutions (PCZ and EPC) added to the column bases and caps section.
Technical Bulletin
Connectors Installed on SCL Columns
T-C-SCLCLMCAN23
A Canadian Limit States technical bulletin addressing typical installations of Simpson Strong-Tie® connectors on SCL columns as well as reduction factors for narrow-face SCL installations.
Technical Bulletin
STHD in PFH Wall Bracing Assembly
L-C-STHDPFH423
Simpson Strong-Tie® STHD holdowns with Method PFH Wall Bracing on 4-inch Wide Concrete Garage Curb.
Engineering Letter

Product Information Table

Fastener Production Information and Stuff & Things
Model No. Ga. W (in.) L (in.) Coating/Material Packaging Qty.
STHD10 12 3 24 5/8 Zinc Galvanized, G90 1
STHD10RJ 12 3 38 1/8 Zinc Galvanized, G90 1
STHD14 12 3 26 1/8 Zinc Galvanized, G90 1
STHD14RJ 12 3 39 5/8 Zinc Galvanized, G90 1

Load Tables

Tension Loads for STHD Installations

Wind and SDC A&B — Allowable Tension Loads for DF/SP/SPF/HF (160)
Min. Stem Wall (in.) Model No. Strap Length (L) le (in.) Required Nails (in.) Uncracked Cracked
Standard Rim Joist Standard (in.) Rim Joist (in.) Midwall Corner Endwall Midwall Corner Endwall
6 STHD10 STHD10RJ 24 5/8 38 1/8 10 (24) 0.148 x 3 1/4 3,535 3,535 1,960 2,910 2,910 1,635
STHD14 STHD14RJ 26 1/8 39 5/8 14 (30) 0.148 x 3 1/4 4,935 4,935 3,065 4,935 4,935 3,065
8 STHD10 STHD10RJ 24 5/8 38 1/8 10 (28) 0.148 x 3 1/4 4,755 4,075 3,015 4,020 3,350 2,480
STHD14 STHD14RJ 26 1/8 39 5/8 14 (30) 0.148 x 3 1/4 5,285 5,285 4,410 5,285 5,285 4,410
SDC C-F — Allowable Tension Loads for DF/SP/SPF/HF (160)
Min. Stem Wall (in.) Model No. Strap Length (L) le (in.) Required Nails (in.) Uncracked Cracked
Standard Rim Joist Standard (in.) Rim Joist (in.) Midwall Corner Endwall Midwall Corner Endwall
  1. Allowable loads have been increased for wind or earthquake loading with no further increase allowed. Reduce where other loads govern.
  2. Concrete shall have a minimum compressive strength of f'c = 2,500 psi.
  3. 0.148" x 3" or 0.148" x 2 1/2" nails may be used as a direct replacement for the required nails shown in the table with no load reduction when they are installed directly over framing or over 1/2" maximum structural sheathing.
  4. Use the number of nails listed in the table or as otherwise specified. In many cases, not all nail holes will be filled. Nail strap from the bottom up.
  5. Deflection at the highest allowable loads for installations over wood double studs is as follows: Installed on framing: STHD10 = 0.117" and STHD14 = 0.118". Installed over 1/2" maximum structural sheathing: STHD10 = 0.146" and STHD14 = 0.164".
  6. To obtain LRFD values, multiply ASD seismic load values by 1.43 and wind load values by 1.67.
  7. Per 2012, 2015, 2018 and 2021 IBC, Section 1613.1, detached one- and two-family dwellings in Seismic Design Category (SDC) C may use “Wind and SDC A&B” allowable loads.
  8. Minimum center-to-center spacing is three times the required embedment, 3 x le, for STHD strap-tie holdowns acting in tension simultaneously. Midwall installation is based on 1.5 x le end distance.
  9. See technical bulletin T-C-SCLCLM for installation on structural composite lumber posts or columns.
  10. For brick ledge applications, use full loads shown for STHD installed in 8" stem wall.
  11. For slab-on-grade installation, use full loads shown for STHD installed in 8" stemwall.
  12. Fasteners: Nail dimensions in the table are listed diameter by length. For additional information, see Fastener Types and Sizes Specified for Simpson Strong-Tie Connectors.
6 STHD10 STHD10RJ 24 5/8 38 1/8 10 (18) 0.148 x 3 1/4 2,750 2,750 1,615 2,550 2,550 1,435
STHD14 STHD14RJ 26 1/8 39 5/8 14 (22) 0.148 x 3 1/4 3,695 3,695 2,685 3,695 3,695 2,685
8 STHD10 STHD10RJ 24 5/8 38 1/8 10 (20) 0.148 x 3 1/4 3,400 2,940 2,295 3,400 2,940 2,175
STHD14 STHD14RJ 26 1/8 39 5/8 14 (24) 0.148 x 3 1/4 3,815 3,815 3,500 3,815 3,815 3,500

Code Reports & Compliance

Drawings

PDF DWG DXF RFA IFC SAT

Related Products

LSTHD
LSTHD
Light Strap-Tie Holdown