On Sun, 30 Nov 2003 19:31:29 -0000, "BillR"
wrote:

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

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