extractor fan install

[steve marchant]

I want to drill a hole through the external wall backing the loo to install an extractor fan assembly. The fan will be in the ceiling, and the duct will go from here in the loft space to the outer vent which will be in the cavity wall.. I don't like heights and would rather drill the vent hole from inside the loft, through the cavity wall to the outside. My worry is the the drill will split the wall on the outside and make a horrible mess on emerging. The chap from whom I will hire the drill and tool assures me that the tool will emerge from the outer wall cleanly without chipping it. Has anyone here had experience of this sort of thing, and reassure me???

[EricP]

If it is a core drill it may emerge cleanly, depending on the operator. It is better to drill a pilot hole and use from both sides though.

If any sort of hammer drill, he is lying and it will smash the bricks off the emerging side if used one way. Again it depends on the operator how much damage is done.

[Palindr☻me]

There is almost bound to be some but I expect that he means not enough to show when the outer draught-excluder plate is fitted over the hole.

You can stick a small diameter pilot hole through first and see what it does, by way of reassurance. If that spalls off a big chunk, then the core drill probably will too..

You can put a marker on the drill at a depth equivalent to the wall thickness and take the last part very gently.

Me, I would put a pilot drill through from the inside, counter-bore at least an inch or so (the more, the better - ideally at least 1/2 a block/brick thickness) from the outside and then bore the remaining depth from the inside - again going gently for the last bit.

[steve marchant]

Can't get up ladders that high, so I'll have to work wholly from inside. Anyway, thanks for useful advice, guys.

[Chris J Dixon]

So how are you planning to install the external shutters/ grille?

Chris