Clive Long,UK wrote:
Hi,

I am going to be hiring a core drill, 6 inch diameter to "pop" a
ventilator through a wall. While I am hiring the baby my thoughts turn
to "popping" a vent above the cooker extractor that currently blows
back into the kitchen and gives me a cold breeze down my neck.

So, what's the minimum diameter whole I need for the cooker hood
vent? I want to keep the hole as small as possible (2-inch?) since the
rash of holes in the wall due to installation of combination boiler
flues make me worry for the wall's structural integrity.

Clive

50mm (2 inch) nothing like big enough. 150mm (6") would be more like it.