Attaching rainwater downpipes to render board

[Richard S]

Hi, we are well on with our self build and I am just starting to put up the gutters and downpipes. Some of the downpipes go onto a rendered finish which is on a render carrier cement board. In a couple of places I don’t have a timber stud behind the cement board where the down pipe bracket is going to be fixed. Can I just attached the bracket to the render board without there being a timber stud behind it? And if so what’s the best sort of screw to use?