Fall towards house

[stick999]

Hi All
I have a mate having a large extension built on the back of his house. The house sits about four feet above ground level which falls away from the house. It is terraced with a retaining wall in front of the house retaining a small patio and steps down to ground level. At the moment the patio falls away from the house.
The builder has told him it is ok to fall the new patio towards the house and to put ACO’s around the house to take the water away. It will be a level threshold. It will be a porcelain patio. Do you think it is a good idea?