Minimum diameter for cooker extractor pipe

[Clive Long,UK]

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

[BillR]

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

[Gary]

BillR scribbled :

My Neff extractor had a 5" (125mm) outlet on top to which I ran 5" flexible ducting to a vent.

[PoP]

Plastic cooker hood venting tube is usually 100mm diameter (a rectangular section of appropriate dimensions is also available). You'd normally drill a hole of 110mm or 117mm to put the tube through

- 150mm is going to be rather large!

Not forgetting that when you drill a large hole in brickwork I would assume it weakens the structure. How much (or little) of a problem that actually is I wouldn't know - but to be on the safe side I would always plump for the smallest hole possible, especially if it is a load bearing wall.

PoP

[Bill Gardener]

I would be interested in hearing what the experts think of this as I have just installed a Bosch cooker hood which required a 150mm hole through the outside wall.

Does a 150mm hole really affect the walls structural integrity???

Thanks,

Bill

[PoP]

Please bear in mind that this isn't something I'm clued up about - I'm just working on the principle that a "whole" wall without a hole in it might be a bit stronger than a "whole" wall with a bit missing :)

I'm interested to know the answer too!

PoP

[BillR]

As most kitchen extractor fans require a 150mm hole (as opposed to toilet fans which are 100mm) I would hope not. About the same as removing a standard brick?

[Clive Long,UK]

Bill

My concern is not a single hole in a wall, I'm sure the circular profile helps distribute the load around the hole, the concern is when the wall already has 4 x 150 mm core drilled holes within, say, 5 metres of each other

Clive

[Brian S Gray]

Domus produce a catalogue in .pdf form which you can download from their website (sorry I have mislaid the URL) and which includes a section on how you calculate what you require. I think the manual that comes with a cooker hood tells you the flow rate required and how the internal fan performs against various flow resistances.