Ducting hole

[rugbyfan2013]

Hi, i am replacing my kitchen hood it should of been an easy job with a straight swap, but the problem is the ducting hole is slightly to small. The hood is going to be ducted straight outside through a double skin masonry wall rendered externally.

The ducting is 125mm diameter, and i guess the existing hole is 120mm diameter, whats the best plan of attack here? I appreciate if i was making the hole for the first time i would hire a core drill etc but as i need to open the hole further im not sure if this is the way to go. Im not sure if there would be enough masonry left for a new core drill to bite properly (never used a core drill before), also i would like to avoid the cost if possible.

I was wondering if maybe i could do something with my SDS drill, sort of stitch drill and hammer and bolster? Any advice would be most appreciated

Also any advice on what to use and how to make good the external render where the ducting grill fits would be awesome

Thanks

 

[jabuzzard]

Hum, I would core drill it out. The problem is the existing hole, so get a sheet of thick sheet material and using a hole cutter cut a 150mm hole in it. Fix this securely to the wall and then use it as a guide to get you started with the 150mm core drill. If you do this from both sides you won't need to make good any render.

 

[jj4091]

If you google "duct reducers" I think you will be able to find what you need, for example http://www.toolstation.com/shop/Ele...d3083/p99431?gclid=CLiV1bOu9LYCFSXLtAoduFIAgw

 

[RogerBoyle]

Hum, I would core drill it out. The problem is the existing hole, so get a sheet of thick sheet material and using a hole cutter cut a 150mm hole in it. Fix this securely to the wall and then use it as a guide to get you started with the 150mm core drill. If you do this from both sides you won't need to make good any render.

First post on here
This advice is wrong the pipe work fittings like the vent cowl will not cover a 150mm core drilled hole
What you need is the 125 to 127mm core drill and not the 117 that did the original hole

 

[jabuzzard]

First post on here
This advice is wrong the pipe work fittings like the vent cowl will not cover a 150mm core drilled hole
What you need is the 125 to 127mm core drill and not the 117 that did the original hole

Getting a 125mm diameter pipe down a 127mm core drilled hole is not going to be easy, if at all possible, it is a 1mm tolerance around the pipe. I you can find one a 140mm diameter core drill might be a better choice.

However if the vent cowl you have for a 125mm pipe does not cover a 150mm hole then get another one that does.

 

[foxhole]

Don't use 125mm ducting, use a reducer to use original ducting.

 

[dhutch]

If you google "duct reducers" ...

So much!

 

[RogerBoyle]

Of course its possible Its the standard size for most extractors fitted in a kitchen these days..

unfortunately most folks that have an existing older extractor tend to have the 4" type with the 100mm hole
And there are no end of folk that think they can just reuse this ..Until they actually read the guarantee and realise that most manufacturers now state that the hole needs to 125mm (5")

You obviously don't fit many extractor vents LOL do you????

if you core drilled at 150 mm you will need to fit a reducer from the Vent to the 125mm pipe that you have fitted to the extractor the only problem is that the 150 mm reducer is 150mm internal measurement....The outer measurement is actually greater and will not fit in the hole
So you are basically making things even worse

 

[foxhole]

Of course its possible Its the standard size for most extractors fitted in a kitchen these days..

unfortunately most folks that have an existing older extractor tend to have the 4" type with the 100mm hole
And there are no end of folk that think they can just reuse this ..Until they actually read the guarantee and realise that most manufacturers now state that the hole needs to 125mm (5")

You obviously don't fit many extractor vents LOL do you????

if you core drilled at 150 mm you will need to fit a reducer from the Vent to the 125mm pipe that you have fitted to the extractor the only problem is that the 150 mm reducer is 150mm internal measurement....The outer measurement is actually greater and will not fit in the hole
So you are basically making things even worse

Everyone I've fitted came with a 5" to 4" reducers , obviously you don't fit many.

 

[dhutch]

But its not a 4inch hole, which I can just about see as its a fair reduction in area (100*100<<125*125) but 120 to 125 is not even ten percent.


Daniel

 

[jabuzzard]

if you core drilled at 150 mm you will need to fit a reducer from the Vent to the 125mm pipe that you have fitted to the extractor the only problem is that the 150 mm reducer is 150mm internal measurement....The outer measurement is actually greater and will not fit in the hole
So you are basically making things even worse

Rubbish, I have just checked and a Manrose wall vent for 125mm spigot has a 160mm grill, which by my calculations is larger than the 150mm size of the core that I suggested drilling.

So just drill the 150mm hole, fit the pipe through, seal it with what ever takes your fancy and fit a an appropriate vet as takes your fancy on the outside.

 

[rugbyfan2013]

Thanks for all the replies guys.

I cant get a reducer and use the old ducting as all the old ducting was the flimsy plastic stuff and was quite badly degraded with holes appearing etc so i threw it out

What i did in the end was to use my sds chisel bit, and took off nibbles where necessary, it worked but not as well as i hoped so i doubt i will being that again lol

I have got a bit of making good to do inside the hole where one brick split and another is quite loose , i was thinking about using some quick setting mortar or concrete for that. What do you think?

Also can u cut the the flexi aluminum ducting and if so whats best? im assuming hacksaw but i thought it was best to check

One last issue i have is where the grill inserts in the external wall the original hole is to big to fix the grill in place, the grill itself overlaps the openings edges but there is no masonry there to put the fixings into, any advice on this? Do you think i could just get away with some mastic or something?

Thanks

 

[RogerBoyle]

if you core drilled at 150 mm you will need to fit a reducer from the Vent to the 125mm pipe that you have fitted to the extractor the only problem is that the 150 mm reducer is 150mm internal measurement....The outer measurement is actually greater and will not fit in the hole
So you are basically making things even worse

Rubbish, I have just checked and a Manrose wall vent for 125mm spigot has a 160mm grill, which by my calculations is larger than the 150mm size of the core that I suggested drilling.

So just drill the 150mm hole, fit the pipe through, seal it with what ever takes your fancy and fit a an appropriate vet as takes your fancy on the outside.

And when you have drilled your hole at 150mm and try to drill the 4 holes on the corner to fix the vent you may well have a problem as there will be insufficient brick ( 5mm Each side to fix a screw into) which is the problem the post above is having

I should also add I make my living by manufacturing and installing bespoke kitchens
So yes I have fitted a few of these things

Yes you can cut down the aluminium ducting by whatever method suits you best
I personally use tin snips

 

[jabuzzard]

And when you have drilled your hole at 150mm and try to drill the 4 holes on the corner to fix the vent you may well have a problem as there will be insufficient brick ( 5mm Each side to fix a screw into) which is the problem the post above is having

Math's fail. A 150mm hole is 75mm radius, a 160mm grill to the corner is 113mm. Specifically it is a right angle triangle of sides 80mm, so the hypotenuse is by Pythagoras sqrt(2*80*80).

That is 38mm in which to fit your securing screw not 5mm and should be perfectly possible. That said if you can find a 140mm diameter core drill that would of course be better, but a 127mm core drill for a 125mm diameter pipe is going to be a very tight fit.

 

[RogerBoyle]

And when you have drilled your hole at 150mm and try to drill the 4 holes on the corner to fix the vent you may well have a problem as there will be insufficient brick ( 5mm Each side to fix a screw into) which is the problem the post above is having

Math's fail. A 150mm hole is 75mm radius, a 160mm grill to the corner is 113mm. Specifically it is a right angle triangle of sides 80mm, so the hypotenuse is by Pythagoras sqrt(2*80*80).

That is 38mm in which to fit your securing screw not 5mm and should be perfectly possible. That said if you can find a 140mm diameter core drill that would of course be better, but a 127mm core drill for a 125mm diameter pipe is going to be a very tight fit.

Tell that to the OP that is currently having the problem where there is an issue with the screws fitting

We will agree to dsagree LOL I'm right and your wrong... Simples

If you are so sure that you are correct then please feel free to experiment on your own house first
Anyway It looks like the OP has taken matters into thier own hands so I'm out of here