Concrete Pan Joist Top Slab Thickness

[mrengineer]

This is a survey: IBC Table 719.1(3) shows 4.6" thickness for 2 hour fire rating when using carbonate aggregate concrete. Do you usually round this number down to 4 1/2" or round up to 4 3/4" or 5"?

 

[SperlingPE]

Up to either 4 3/4".

 

[lkjh345]

Round up to 5".

 

[SperlingPE]

5" may certainly lead to less mistakes in the field.
However, that 1/4" of concrete can be a savings depending on the size of the building.

100'x200x1/4" is 15+ yards of concrete

50'x50'x1/4" is almost 2 yards of concrete

 

[JAE]

I seem to remember the older UBC codes had 4 1/2". I have designed numerous buildings using 4 1/2" for the thickness.

 

[lkjh345]

1/4" of concrete, assuming $150 per cubic yard for concrete material (assuming finishing is a wash) amounts to about 12 cents per square foot to the building.

Meanwhile, the Interior designer is trying to decide between the quarry tile at $5.00/SF or the marble tile at $10.00/SF.