| Fasteners and Connections Screws Self-drilling screws are the most common fasteners used to frame TradeReady® floors. Screws are available in sizes ranging from #6 to #14, with #6 to #10 being the most common. Screws are generally 3/8 inch (9.5 mm) to ½ inch (12.7 mm) longer than the thickness of the connected materials. The point at the end of the screw must be sharp enough to penetrate the steel. Self-drilling screws have drill points at the end of the screw with no threads. It is important that the drill point be as long as the material thickness being fastened to drill effectively. The correct fastener type and length for each application should be selected by consulting the screw manufacturer’s specifications and catalogs. TradeReady® steel construction typically utilizes self-drilling screws. |
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Drive Types
Drive types are usually determined by availability and preference. Some common drive types include:
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Thread Self-piercing and self-drilling screws intended for TradeReady® steel applications generally have a coarse thread (e.g. 10-6 x 5/8 HWH SD, would indicate a 10 diameter, 16 threads per inch, 5/8" length, hex washer head self-drilling screw). There also are many drill screws that have fine threads for drilling thicker steel. Product specifications should be supplied by the manufacturer of each screw specified. The accepted tolerances for coarse and fine self-drilling screws is contained in SAE178. |
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Steel Framing Screws Pan head, self-drilling screws are commonly used to connect TradeReady® joists and blocking. No. 10, ¾-inch (19mm) hex-head, self-drilling screws are used on thicker steel materials. No. 8, ½-inch (13 mm) self-drilling screws with low profile heads (such as pancake heads) are used when rigid sheathing or finishing materials (such as plywood or gypsum board) are installed on top of the screw head. Sheathing Screws Sheathing screws are used to fasten sheathing (such as plywood, OSB, or drywall) to Trade Ready joists by drilling in both layers of steel and wood. Selecting the right screw type and length depends on the material being connected to steel, thickness of that material, and thickness of steel. A sheathing screw should penetrate the sheathing and steel framing first before engaging the threads to pull the sheathing material tight towards the steel. A depth-sensitive nosepiece on the screw gun comes in handy and, in some cases, is a necessity to prevent over drilling through the sheathing layers. No. 8 self-drilling screws with pilot points are generally used on plywood floors fastened to TradeReady® joists. Self-drilling screws with bugle heads are designed to countersink slightly in the gypsum wallboard, plywood sheathing, or finishing material without crushing the material or tearing the surface. Bugle head screws leave a flat, smooth surface for easy finishing. Water head screws have larger heads than flat head screws and are typically used to connect soft materials to TradeReady® joists. Flat head screws are designed to countersink and sit flush without causing wood floors or finishes to splinter or spill. Gypsum board is generally fastened to TradeReady® framing with #6, self-drilling bugle head screws (known as drywall screws) with a depth-setting nosepiece to avoid piercing the gypsum board. |
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Screw Requirements For all connections, screws should extend through the steel a minimum of three exposed threads. Screws should penetrate individual components of a connection without causing permanent separation between the components. Screws should be installed in a manner such that the threads and holes are not stripped. Self-drilling tapping screws should have a Type II coating in accordance with ASTM B633 [1] or equivalent corrosion protection. |
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Steel-to-Steel Connections Screws for steel-to-steel connections (such as TradeReady® rim to TradeReady® joist connection) should be installed with a minimum edge distance and center to center spacing of ½ inch (13 mm), and shall be self-drilling in compliance with SAE 178 [2]. |  |
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Wood-to-Steel Connections Structural sheathing (such as plywood or OSB) should be fastened to TradeReady® (i.e. joists) with minimum #8 self-drilling screws in compliance with SAE J78[2]. Screws connecting structural sheathing to TradeReady® steel joists should have a minimum head diameter of 0.292-inch (7 mm) with countersunk heads. The screws should be installed with a minimum edge distance of 3/8-inch (9 mm). The screw size is determined based on the steel thickness as specified in Table 1. A pilot point self-drilling screw is a specially designed screw used to attach plywood TradeReady® joists. The screw has threads that start approximately ¾ inch (19 mm) up from the drill point to ensure that the spinning screw goes through the plywood and does not climb the drive. Instead, the screw penetrates the steel, and the screw threads engage in the metal for tight fit. |
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Steel-to-Concrete Connections Anchoring TradeReady® steel floors to the foundation is generally accomplished in a manner similar to wood framing. The most common anchors used in steel floor construction are anchor bolts, mudsill anchors, anchor straps, mushroom spikes, and powder-actuated anchors. Bolts should meet or exceed the requirements of ASTM A307[4]. Washers and nuts should be properly installed and tightened. Bolts connecting TradeReady® rims to concrete shall have bolt holes spaced a minimum of three bolt diameters on center. The distance from the center of the bolt hole to the edge of the connecting member shall not be less than one and one-half bolt diameters. |
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| Dietrich Metal Framing, Inc.
Corporate Headquarters 500 Grant Street/Suite 2226 Pittsburgh, PA 15219 Phone: (412)281.2805 E-mail: askforhelp@dietrichindustries.com |
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