Holding it All Together: Designing, specifying, and installing connectors

It is critical to specify the right fastener to ensure the proper performance of the connections in light-gauge (cold-formed) steel. The most common and widely used connection methods are screw connections, powder-actuated fastener connections, and welded connections.
Photo courtesy Steel Framing Industry Association

General instructions for the installer
These general instructions are in addition to the specific installation instructions and notes provided for each particular product, all of which should be consulted prior 
to and during installation of any manufacturer’s pre-engineered, premanufactured product.

1. All specified fasteners must be installed according to 
the instructions in the manufacturer’s catalog. Incorrect fastener quantity, size, type, material, or finish may cause the connection to fail.

2. Holes for 13-mm (½-in.) diameter or greater bolts 
shall be no more than a maximum of 1.5 mm (1/16 in.) larger than the bolt diameter per AISI S100 Table E3a, Appendix A.

3. All specified fasteners must be installed before loading 
the connection.

4. Some hardened fasteners may have premature failure if exposed to moisture. The fasteners are recommended to be used specifically for dry interior applications.

5. Proper safety equipment must be used.

6. When installing a joist into a connector with a seat, it shall bear completely on the seat. The gap between the end of the joist and the connector or header shall not exceed 3 mm (1/8 in.) per International Code Council Evaluation Service (ICC-ES) Acceptance Criteria (AC) 261, Connectors Used with Cold-formed Steel Structural Members, and ASTM D1761, Standard Test Methods for Mechanical Fasteners in Wood, unless otherwise noted.

7. For holdowns, anchor bolt nuts should be finger-tight plus a third- to half-turn with a hand wrench. Care should be taken to avoid over-torqueing the nut or using impact wrenches, as this may preload the holdown.

8. Holdowns and tension ties may be raised off the track as dictated by field conditions to accommodate an anchor mislocated no more than 38 mm (1 ½ in.). The holdown shall be raised off the bottom track at least 76 mm (3 in.) for every 6.4 mm (¼ in.) the anchor is offset from the model’s centerline. Anchor bolt slope shall be no greater than 1:12 (or five degrees). The designer should be contacted if the holdown anchor is offset more than 38 mm or raised more than 457 mm (18 in.). Raised holdown height is measured from the top of the concrete to the top of the holdown bearing plate.

9. All screws shall be installed in accordance with the screw manufacturer’s recommendations. They must penetrate and protrude through the attached materials a minimum of three full exposed threads per AISI S200 General Provisions Section D1.3.

10. Since welding galvanized steel may produce harmful fumes, proper procedures and safety precautions must be followed. Welding should be in accordance with American Welding Society (AWS) standards. The manufacturer’s installation guidelines should be consulted to verify the specific connector in use can be welded.

11. Temporary lateral support for members may be required during installation.

Considerations for specifying clips and connectors
There are a few factors to consider when specifying clips, but most importantly are the clip itself and the manufacturer producing the product. As previously mentioned, connectors are considered structural elements, and play a vital role in the design of modern buildings by helping ensure buildings are safe even when subjected to high winds and seismic forces. Therefore, it is necessary to specify for quality assurance (QA).

Quality assurance refers to the procedures for obtaining 
data indicating performance, properties and other attributes meeting the requirements. This includes manufacturer qualifications, engineering responsibility and qualifications, product test reports, and evaluation/research reports.

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