How to duct rangehood thru Asbestos Roof?

[anotherenovator]

hi there, i've been reading a fair bit on this forum for my house renovation and firstly just want to thank everyone that's posted for their great info!

i'm on the home run in getting our new kitchen together and need to finalise ducting for the kitchen rangehood.

I'm pretty confident to give this a crack myself except unsure which kit/parts i should use for the job. i've seen at bunnings and other places a 150mm kit with flexible durcting which vents thru the roof with flashing and all you do is remove a single tile. However, i've got concrete sheets (asbestos) on my roof so i imagine the job will be slightly different. Handling asbestos doesn't worry me as i have the right safety equipment but would someone please recommend the parts or kit most suitable for this job? thanks heaps.

edit: i'm having difficulty finding a 150mm kit, can anyone suggest where they can be found in brisbane?

[davo2310]

personally, I would manufacture my own lead apron, then fit a fire rated decktite over. that would be for my house.

[BobL]

. . . . . However, i've got concrete sheets (asbestos) on my roof so i imagine the job will be slightly different.

Given that your own words you have only ever "imagined" doing this, I think you have put it rather mildly. I would be interested to know your imagined methodology for doing this.

[anotherenovator]

Given that your own words you have only ever "imagined" doing this, I think you have put it rather mildly. I would be interested to know your imagined methodology for doing this.

That's a good question. I was imagining getting a spaceship to come down and using it's laser beams cut the suitable hole through the roof, before allowing the green pig to get inside and arrange installation of the flue. This may not be the same method others would use, but i reckon it'll do the trick.

thanks for your constructive and insperational feedback. I am, however, looking for some help with the said situation.

[anotherenovator]

personally, I would manufacture my own lead apron, then fit a fire rated decktite over. that would be for my house.

thanks, Davo. that sounds pretty good. i didn't know lead was still avaliable.

[ausdesign]

I don't know if this fits your situation [or restrictions] but with venting of a rangehood I would be looking at 90mm pvc pipe directed to the eaves with a screened grill [ to stop crawlies ].
The pvc should have a fall - even slight - to the eaves & should only be cold joined so that if need be in the future it can be removed to clean out gease etc. I would not in any circumstances use ' concertina' type ducting.

[anotherenovator]

I don't know if this fits your situation [or restrictions] but with venting of a rangehood I would be looking at 90mm pvc pipe directed to the eaves with a screened grill [ to stop crawlies ].
The pvc should have a fall - even slight - to the eaves & should only be cold joined so that if need be in the future it can be removed to clean out gease etc. I would not in any circumstances use ' concertina' type ducting.

Your info sounds very interesting. What you've stated contradicts a little with info i've gathered so far. But as i'm a range hood ducting virgin, you likely know your stuff a lot better than i do! Here's what i understood was required:
- 150mm ducting. i've heard that smaller size ducting and long ducting over 3m (which i'd need to do to get to the eaves) would restrict the flow of air/gas quite significantly and therefore reduce the sucking performance of the hood. I've also heard never to use plastic to vent kitchen gasses. I have also heard from many others never to use concertina type ducting as you have also mentioned.

So i'm still a little unsure on the best way to do this job...

[journeyman Mick]

I would get someone else to cut the AC roofing (I absolutley refuse to touch it). I'd run a metal flashing down from under the ridge to past where the flue would penetrate the roof. I'd penetrate this, slightly larger than the ducting, turning the edge of the hole up a few mms with multigrips. If you ony turn up a few mm you can stretch the metal without tearing it. Run your flue through the hole and use a dektite collar over the flue and down onto the flat metal flashing. Dektite is sealed to flashing with silicone. If the silicone ever breaks down (unlikely) any water that manages to make its way between the flashing and the rubber collar will be deflected around the hole by the turn up. The metal flashing would be turned down along ther edges to fit into the corrugations (I assume you have the old "super 7" roofing) and scribed to fit into the corrugations at the bottom edge. If you do a search you should find a post by Cliff Rogers showing how he did this through a corrugated metal roof. It has pictures showing how he did it.

Mick

[anotherenovator]

...If you do a search you should find a post by Cliff Rogers showing how he did this through a corrugated metal roof. It has pictures showing how he did it.

Mick

thanks mate, i just checked out the thread. that seems pretty easy to follow. now i just need to find the parts...

[journeyman Mick]

............. now i just need to find the parts...

The dektites are carried by any decent hardware or plumbing supplier and any sheetmetal shop should be able to cut and press a suitable flashing. You could even ghet them to make you a "chinaman's hat" to go on top of the ducting. If there is a "Tekform" distributor where you are they should have a range of different rangehood ducting, both round and rectangular.

Mick

[SilentButDeadly]

I second the Dektite approach but you'll have an interesting time cutting through your roof sheet.....power drill, masonry bit, water spray bottle & paitience I suppose.

Using an eaves vent through the soffit (if you have one) might be preferable.

Your local Reece, Plumbtec or Tradelink shop will carry all the rangehood ducting parts and roof penetration parts you'll ever need...often in a shop display stand...I too would be avoiding the flexible ducting as much as possible.....the fan will run better/suck more air through a solid pipe.

[Daren]

Theres a mob called Uniduct that sell kits for the ducting,
call this number and tell them what your situation is and what you want 1800 648 556, they will tell you the parts you need and you should be able to get them from your local retravision or Hardly Normals etc.

I got a 150mm kit off them, havent installed it yet though.

google Uniduct to get an idea