The self-drilling screw is a non proprietary option for connecting the sidelaps of adjacent steel deck sheets. The screws have a self-drilling head and are installed with a standard screw gun. The head of the screw drills through the two layers of light gage steel until the threads engage and draw the sheets together. The shear strength of a sidelap connected with self-drilling screws is relatively low compared to the stronger alternatives [PunchLok (VSC) or TSW]. Diaphragms utilizing self-drilling screws at the side laps often cannot meet the higher shear requirements of West Coast, seismic driven design.
When self-drilling, self-tapping screws are used to connect the sidelaps of HSB-36-SS and N-24-SS roof decks, they are to be a minimum #10 x 3/4-in. long. The diaphragm shear values and flexibility factors shown in Verco’s literature for deck fastened with button punches can be used for screwed sidelaps provided the screws are placed at the same spacing as the button punches.
Spacing of the attachments at the collectors parallel to the deck ribs is based on the type of attachment being used. The maximum spacing of attachments at parallel collectors is 3 feet (36 inches).
How to Specify Screwed Sidelaps for Interlocking Deck
If your design includes any of Verco’s interlocking deck profiles (B, N, W2, or W3) and sidelaps attached with self-drilling screws, make sure the “SS” version is specified. For example, if you want to specify HSB-36 with screwed sidelaps, call out HSB-36-SS. The “SS” designation indicates deck provided with an extended female lip for screw fastening (see photo below). This does not apply to Verco’s nestable deck profiles (Shallow VERCOR or Deep VERCOR) as they have sufficient space for screws at the sidelaps.
**IMPORTANT NOTE: Sidelaps of “SS” deck can only be fastened with screws; no other sidelap attachment type can be used on “SS” deck.**
Sidelap screw installed on HSB-36-SS. Typical sidelap screw.