Usage of vibrator during roof casting

[jackalbda]

During roof casting, is the vibrator used everywhere or just inside the beams ? My contractor is saying that vibrator will not be used in the normal flat areas of the roof (it might vibrate the metal sheets used for centring and may loose its alignment ,he says) but only within the beams . In the normal flat area, the rcc is just poured over and they do just leveling ( not even using steel rods to poke it ). I am not sure if vibrators will be used in the flat area of a roof but I have seen the steel rods being used to poke the RCC . Is it done only if the RCC is more than some thickness or something ? Mine is a pillar construction.

[msn1270]

Usually there will be air gap and excess water upto 20% in any wet concrette activities based on the materials and the ratio used for mixings. These gaps reduces the strength of the structure in the long run.

Vibrator to be used even for the Roofing without any doubt. But they must ensure to use the Steel plates based shuttering to have better strength.