Extending my RCC roof.

Dear Ashok

       I think that you have left the steel bars from old slab for new slab. If this is the case than overlap the steel bars of old slab and new slab and the over lap length should not be less than 50d. In case you have not left the steel bars than give bearing of the new slab atleast 4'' on the wall and the surface of the old slab should be cleaned and cured before laying the new slab. For more instruction about RCC please visit the website gharexpert. com conc subsection in construction section.

Dear Ashok

         It is not necessary to weld the bars, tye them with binding wires. If you want to weld these bars than care should be taken that the new bar must overlap in 2 feet length and welded at least on three to four points, avoid neck to neck welding i.e. end to end welding which is harmfull.

Dear Ashok

         There is no need of any chemical to be applied on the old concrete. you should clean the old surface by brush or broom and roughend it by chiseling and wash throughly. Then cure the old concrete and kept it wet by wrping with wet gunny bags well before 2 -3 days before laying the new slab. At the time of laying the slab put shullury of cement and water on the old surface and proceed further laying the RCC slab of your dream home.