fitting an extractor cowl from the inside

tataylor1 · 3 Dec 2013

Hi all.

Wasn't sure where to put this post so hopefully it's in a suitable category.

Does anyone know of a product or a clever technique they've come across for fitting a weather cowl on an extractor fan outlet - from the inside?

I'll be fitting an extractor to draw moisture from the bathroom, through the ceiling, into the loft space and out the loft exterior brick wall. Everything is simple enough except fitting a weatherproof cover on the hole in the brick work. I'm right at the top of the house and don't have a ladder that would reach on the outside.

If anyone has a bit of useful advice that would be great.

Cheers

tataylor1 · 3 Dec 2013

just found this on the forum actually

http://www.plumbworld.co.uk/greenwood-airvac-100mm-fast-1944-17115

so will start there......

Burnerman · 3 Dec 2013

That ducting does look to be very effective - it should keep the birds / insects etc at bay.
Fans are also available which have internal louvres, so helping prevent back draught.
The problem you are faced with is the break through of the brickwork at the outside....even though you will need to use a core drill, there's really a need to seal the outside of the ducting to the brickwork.
John

tataylor1 · 3 Dec 2013

Cheers John.

From the looks of it there are rubber gromits on the pipe and they might help to a point. Then I was imagining smearing/packing mortar in as best I can.

It wont look amazingly pretty from the outside but it will be high and not in obvious sight. It probably wont look too smart from the inside but as long as its watertight for rain and wasps etc that's fine.

Would mortar be the best thing here? I'm drawn to expanding foam but that would look pretty terrible from the outside.

Burnerman · 3 Dec 2013

If you are drilling through from the inside, you have to penetrate the cavity wall - so you may be able to seal the inner leaf but not the outer.
The only way to help this would be to cut a bigger hole in the inner leaf, and then seal from within, if you get my drift.
For larger break outs, sand and cement is the way - for filling clearances from the drill, silicone is the one.
Can you hire some long ladders, and a friend, maybe?
John

foxhole · 3 Dec 2013

Have done this a few times, drill small [8mm] hole right thru from inside 10mm below intended hole site.
drop a line thru and attach bucket outside and pull up to just under drill site [square bucket best].
Drill hole from inside clear as you go and breakout will fall into bucket.
Lower bucket and empty.
Drop a weighted line thru the hole and pull up out cowl , you can run silicon around inner face of cowl either before pulling up or thru the hole once pulled up.
Cowl needs two pieces of string or cable ties attached to help position and then tie off inside till set.
Then you can add liner etc from inside before fan install.

phatboy · 3 Dec 2013

foxhole said:
Have done this a few times, drill small [8mm] hole right thru from inside 10mm below intended hole site.
drop a line thru and attach bucket outside and pull up to just under drill site [square bucket best].
Drill hole from inside clear as you go and breakout will fall into bucket.
Lower bucket and empty.
Drop a weighted line thru the hole and pull up out cowl , you can run silicon around inner face of cowl either before pulling up or thru the hole once pulled up.
Cowl needs two pieces of string or cable ties attached to help position and then tie off inside till set.
Then you can add liner etc from inside before fan install.

Now thats a pretty clever idea!!

tataylor1 · 4 Dec 2013

Thanks all. I have purchased the above fitting so will assess it and might try the pull-up string option.

It's a good idea. But as i imagine it it would be rubbing against the exterior wall the whole way up. Possibly leaving a silicone trail? I might pull it up through a piece of copper pipe that extends out of the hole in the brick work. Effectively pulling it up vertically then when its level with the large hole i pull the whole thing in sideways.

Thanks for the idea

foxhole · 5 Dec 2013

tataylor1 said:
Thanks all. I have purchased the above fitting so will assess it and might try the pull-up string option.

It's a good idea. But as i imagine it it would be rubbing against the exterior wall the whole way up. Possibly leaving a silicone trail? I might pull it up through a piece of copper pipe that extends out of the hole in the brick work. Effectively pulling it up vertically then when its level with the large hole i pull the whole thing in sideways.

Thanks for the idea

You could wrap in a carrier bag and rip off when it gets to the top.I prefer to put the silicon on thru the hole.

phatboy · 14 Dec 2013

Have you tried this yet? Interested as to if it worked

tataylor1 · 18 Dec 2013

Ahoy there! Yeah it seemed ok.

I ended up drilling several small holes to punch through my large hole as the core drill bit I have wouldn't seem to do it - not an expensive one.

So i drilled my first small hole at the bottom of the circular hole i needed, fed a line through and pulled a bucket up and then secured this within the loft so it was tight against the exterior wall, at a right angle. Then drilled my other small holes, each time the drill exiting into the cavity of the bucket. Still with me? Then punched the brick through, into the bucket. Untied and lowered the bucket and proceeded to fit the cowl and pipe.

I used the previously mentioned item from plumbworld and it seems ok. Excessive use of silicone required though.

All in all its a big improvement from what I had, which was a long length of flexi which just collected condensation

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fitting an extractor cowl from the inside

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