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Purpose of non-structural topping over PC planks
2

Purpose of non-structural topping over PC planks

Purpose of non-structural topping over PC planks

(OP)
I have a proposed floor with 10" pre-cast floor planks topped with 2" non-str conc topping. The arch asked if we could get rid of the topping and she can use a wood flooring instead as a finish. My response was that the 2" is nominal and it varies a bit across the span of the plank and is basically there to provide a leveled floor. Was I right? I always thought of this topping as a tool to provide a level floor in a plank that has camber/deflection.

RE: Purpose of non-structural topping over PC planks

It is a composite system. Check your load tables and you will see that a plain 10" plank won't carry as much as 10" + 2".

RE: Purpose of non-structural topping over PC planks

(OP)
ron, the topping is non-bonded non-structural.

RE: Purpose of non-structural topping over PC planks

You are correct for that and other reasons. The hollowcore has gaps (which are grout filled) which are likely to be uneven. The hollowcore itself has a very rough finish that the wood floor might not adhere to. It adds strength. And finally:
WHY DOES YOUR ARCHITECT CARE?

RE: Purpose of non-structural topping over PC planks

Typically 2" toppings are structural. The tops of hollow core planks are roughened and the bonded topping serves to increase load capacity, level the floor and also to provide a better diaphragm behavior.

Without the topping there will be irregular joints and a curved (cambered) floor level. Also, the topping is used as a cap and means of connecting the plank system to supporting walls.
Without the topping, the connection between wall and plank is more difficult.

RE: Purpose of non-structural topping over PC planks

Seems to me that a minimum of 2" bonded topping constitutes a rigid diaphragm floor, otherwise it's not a rigid diaphragm unless suitable mechanical connections between panels are provided.

RE: Purpose of non-structural topping over PC planks

(OP)
Thanks all.

Jed...the architect believes that taking out this topping will save money. She is unwilling to re-think about the arched (actually semi-circular) doors on both entrances and some other rather lavish features but removing topping is supposed to make up for that.

RE: Purpose of non-structural topping over PC planks

Not sure about some comments. Non structural is non structural but it does provide a level floor as the Planks are cambered and also serves to disperse point loads so not to overload the holes in the planks. In uk they can be tied together

RE: Purpose of non-structural topping over PC planks

But I will say your architect sounds like an idiot

RE: Purpose of non-structural topping over PC planks

Non-structural topping is just for leveling. I don't know what type wood flooring the architect is proposing, but if it is just a floating floor, the untopped planks will not provide an acceptable substrate.

RE: Purpose of non-structural topping over PC planks

Sorry... I didn't see the little, non-important noting of the topping as being non-structural in the subject line.

I have cleaned my glasses.

Mike McCann
MMC Engineering
http://mmcengineering.tripod.com

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