Flat roof drainage

[langers73]

I have recently had an extension built. It has a flat roof with raised edges and a slight slant to allow for drainage to a main gutter. The drainpipe from the roof of the main house goes straight onto the flat roof meaning that the water from the main roof will end up on the flat roof then draining to the gutter on the extension. Is this normal?

Is this ok for all the water from the main roof to go straight onto the flat, not directly to the gutter in the extension



Flat roof (apparently) has 3 layers of felt



Any advice would be great.



Many thanks

 

[DAZB]

It is not best practice to do that and far better for the water to be removed to the drains by the shortest or quickest route possible and i would say dropping it onto a flat roof is only going to create problems somewhere down the line.

 

[noseall]

Is this ok for all the water from the main roof to go straight onto the flat, not directly to the gutter in the extension

Yes, no problem.

 

[freddiemercurystwin]

It can depends on many factors, where the existing rwp's/drains are, how big is the extension etc, a before and after photo would help.