Waste pipes above ceiling in new extension

[gpbeck]

Hi guys
I have expressed an opinion on this waste plumbing which is by a builder on an extension to a terraced house belonging to a relative. My opinion has not been received well so what do we think? The new black pipes will soon disappear under a pitched roof brought across from the left. The narrow pipe, apparently 40mm drains just a sink upstairs. There is a vertical 110 mm going down in a 300mm gap between the 2 houses.

Thanks for your opinions!

 

[ShaunCorbs]

Flat roof on the extension?

 

[gpbeck]

No pitched so covering this.

 

[ShaunCorbs]

Bit high for flashing on the window