Winging It

In preparation for securing down the mezzanine floor, I headed down to the local hardware store to purchase some wood to metal screws. These are the ones with a drill bit built into the tip of the screw, and a countersink phillips head.

They had bags of 250 for $36, and boxes of the same – 500 for $37. Pays to look at increased bulk I guess, but still it reeks of something.

These need a predrilled and countersunk hole in the redtongue, otherwise they tend to damage and crush the top surface, pull themselves through the timber, causing it to lift until the drill tip penetrates through the steel, and by that time the screw head had buried its way deep below the surface.

What I wasn’t aware of is there is a better way, and these are the screws the electrician was using. Guess it shows how often I deal with steel structures.

These screws cost $23 for 500 from Peninsular Bolt, so a significantly better deal, for a superior screw.


These are still made with the drill bit tip, that primarily is designed to drill through metal. At the other end, the conical top had ridging on its underside, so this screw self-countersinks. Already a bonus.

Where the screw gets clever is those two wings near the drill-bit-like tip. They are initially larger than the hole being drilled. While passing through the initial layer of timber (such as flooring), these wings cut a hole that the thread doesn’t get to touch.

However, that would be no good for us if that went all the way – what would the threads bind on?! What happens instead, is those wings once they have passed through the timber, they snap off when in contact with the metal.

So they work well, with no requirement for predrilling, countersinking etc. These will do it all.

They will be a real timesaver when I get to screw down the mezzanine flooring.

5 Responses

  1. Don’t forget to pull your joists square to the bearers & flooring Screws should be ( should be) climaseal 3 @ 200 ctrs. Use a Ping line to line up the screws

    • Looks like sound advise. Just don’t actually know what is meant by the first, and never heard of climaseal. I know what 200 ctrs and ping line mean though!

      • Just looked up Climaseal – not sure why that is needed for an internal application, with no exposure to the elements. Isn’t the zinc coating on the screws sufficient for this application?

  2. Actually Barry is spot on with squaring up the bearers as the Z-sections the builder has used are not designed for load bearing and cause what we call ‘crazing’ that’s the lean that happens on the top flange of the Z-section when you load them up, they should have used C-sections. What is going to occur now is that instead of the screws just holding down the structaflor they will also have to counteract the moment on the steel and hold it square therefore the more you load up the mezzanine floor the more these adverse forces will be applied to the screws

    • Ah- that makes sense (thanks Barry and Graham)

      I particularly noted that when looking at the materials, and when the floor joists were installed. Stupid, stupid design. Standing on them unsupported, and their complete lack of structural integrity is astonishing. Must be a civil engineering thing – a mechanical engineer would never have proposed such as design concept 😉

      There was one rotated the other way around from the builders’ installation, and I have rotated another, so two are counteracting that tendency, so the floor should now be pretty stable, and not inclined to….uh….incline.

      Combine that with the flooring, and plenty of screws, and we’ll be right for loading the floor up. Don’t remember exactly what it is rated for – will have to find out.

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