Hole for bathroom extractor fan

[operon]

Hi all,

I have a fan wired in already, I was going to get the guys who did my tiling & plumbing to fit it to the wall but I'm not entirely happy with their diligence so I'm thinking of doing it myself.

It's wired in right next to an existing passive vent, the plan being to use that. However there's a couple of issues.

1. The internal hole isn't big enough and needs widening.
2. It slopes upwards slightly, which is bad for condensation reasons right?

What would be the best way to proceed? It's not a cavity wall (I wish... brrrr) which makes this a little simpler I guess. Any tips would be much appreciated.

Cheers,

Andrew.

 

[JohnD]

Hire a Core Drill from your local plant and tool hire shop. Get a 105mm or 110mm core that you can fit a duct (or piece of soil pipe) through and mortar it into the wall at the ends.

You will probably find it easier to cut a new hole than make the old one bigger as the core will rattle about with nothing to steady it.

If your old vent is smaller than that it must be unusually small. Or have you got a 150mm fan?

 

[operon]

It is a 150mm, but also there is some sort of false ceiling in the bathroom which comes down to half way down the internal vent hole, so only half the hole is accessible. It's wide enough but only half the height.

Maybe a new hole would be the way to go after all.

Andrew.

 

[JohnD]

You should be able to hire a suitable core drill. Buy the duct first so you can take it to the hire shop and check the core is the right size (a close sliding fit is best).

It is an easy job but slow and fairly dusty (not as bad as an angle grinder or scrabbler).

You will get a neat finish on the side you drill from - it makes a pilot hole, if you can drill from both sides this will be neatest in case the outer brick breaks away. You need to have a firm footing on good steps or something as it is heaby and you lean against it until it breaks through.

To meet the electrical safety zoning rules will be easier if it is not directly above a bath or shower (unless it is 3m+ above the floor or extra-low voltage) see this link

 

[operon]

Okay, I'll look into that. From the outside I can brace myself againt the opposite wall (it's an alleyway) but I'd rather get a neat finish on the inside... Is there a knack to getting it to go in at an angle?

Andrew.

 

[JohnD]

There is a pilot drill in the middle that sticks out further than the "can" of the core drill... so you put that in first at the angle you want, and the core will follow it.

The day you hire it, cut any other holes you might want for extractors, tumble driers, ventilators etc as it's so easy.

The core drills are very expensive to buy.

 

[2scoops0406]

You can widen the hole by drilling a correct size hole through a sturdy piece of timber. The timber is centrally attached to the wall over the undersized hole, securely you then proceed as normal. It's a pain that the angle of the hole needs to be adjusted as well, but as long as the wood is secure, you'll manage.

 

[operon]

How about drilling in from outside, starting slightly lower than the level of the fan, and going up into the shaft of the existing ventilation gap from below? Would that work? Slightly hard to describe without a diagram -- let me know if you have no idea what I mean, and I'll draw one.

EDIT: I have just notice that because the passive vent is over the bathroom window, there's a lintel just underneath it. Is drilling a bloody great hole in a load-bearing member a bad thing? Something tells me it might be.

Andrew.

 

[JohnD]

Yes.

And for a few courses above.

Put it somewhere else. As far from the door as poss so you get through flow of air.