thickness of concrete on metal decking


I am pouring a slab on a suspended metal deck. I am using Three inch decking with a maximum span of nine feet. The steel supplier told me I need to pour six inches of concrete for this size decking. Is this thick enough?


The thickness of slab is determined by how much load the slab is going to carry. A 20 gage floor deck normally can span up to 10ft, the 9ft span is about right. For 6 inch thick total slab thickness should be ok for normal residential loading as long as there is no heavy equipment on the slab.

Don't forget to put reinforcements either rebar or wire mesh.

If you have single span deck, meaning your entire pour is 9ft wide such that no beam in the middle. In that case most deck manufacturer recommend shoring/bracing the deck to make it double span thus increasing its strengthen. The shoring is only temporary until the concrete receive it's full strength.

I have seen single span deck buckling in the middle of the pour due to the weight of the concrete. Believe me this is not something you want happen during your pour. If this happens the only fix is throw away everything and start over. So if disaster happens damaged deck and concrete are not reusable, likewise lost time in labor and concrete pumping. It is better to be over prepared so as to be on the safe side.

Make sure the concrete is evenly distributed during the pour, for that reason using concrete pumping services is always recommended for metal deck pour.

The challenge with pouring metal deck without a concrete pump, you risk damaging the metal deck when the concrete allowed to pileup in one location before moving them to hard to reach areas. The unbalance loading of the metal deck will cause deck failure.

Hope this helps
Good Luck

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