TEK Screws for Outdoor Use

[PT999]

I have been asked to inspect an outdoor installation where the the designer called for #12 TEK Screws attached to structural steel HSS tubes. The screws support photo voltaic racks.

My view is these screws, although they pass structural analysis, are simply not appropriate to be used in an outdoor environment, because they will corrode.

Any comments, I am also wondering if this connection to 3/8" thick tubes works also, as these screws are usually attached to sheet metal. The tread spacing is going to be smaller than the steel thickness.

 

[Tomfh]

TEKS are commonly used outdoors. It's how they fix roofing.

You can drill into steel that thick, but it's harder. You need the right fasteners and drill.

The thread spacing can be smaller than the base steel, and this is a good thing, because the base material acts as the "nut". More threads engaged = more strength. Here is a table showing pullout loads for steel up to 1/2 inch (12mm).

http://www.buildex.com.au/support_techspecs.html

Obviously, being smaller, they mightn't last as long as say a bolt, but they can last.

Watch galvanic corrosion though. That can rapidly accelerate corrosion failure.

 

[Ingenuity]

TEKS Series 500 are able to drill through and attach to 3/8" thick structural steel, and there are some options re corrosion protection like "ClimaSeal" for marine, coastal or severe conditions.

Self-drilling screws and cordless impact guns have revolutionized on-site cold formed steel framing connections.

 

[XR250]

The #12 TEK 5's I used in my house were hot dipped.