150mm hole - close to the edge

[Diggory]

Hi all - after a bit of advice please.

I need to core out a 150mm extractor round duct (so 160ish hole).
Taking floor height, hob to extractor, etc, etc into account -
I’m coming close to the top of my external wall - maybe two courses down.

It’s a new soft red wall that non load bearing - there’s a stud wall inside.
Even done gently - I’m a bit concerned that the hole could blow / break open.

Do you have a rule of thumb on how close to top of wall it’s safe to core out a hole of this size.

Thanks D

 

[Notch7]

Hi all - after a bit of advice please.

I need to core out a 150mm extractor round duct (so 160ish hole).
Taking floor height, hob to extractor, etc, etc into account -
I’m coming close to the top of my external wall - maybe two courses down.

It’s a new soft red wall that non load bearing - there’s a stud wall inside.
Even done gently - I’m a bit concerned that the hole could blow / break open.

Do you have a rule of thumb on how close to top of wall it’s safe to core out a hole of this size.

Thanks D

is it bungalow or a single storey extension

is it flat roof above or pitched?

personally I would think it would be ok, core drills cut quite gently really, just dont use too much force and let the diamond edges do the cutting without too much pressure

Ive not got much experience with core drills, I dont know if you can start from the inside then once the centre guide drill gets through, finish off from outside

 

[noseall]

Hi all - after a bit of advice please.

I need to core out a 150mm extractor round duct (so 160ish hole).
Taking floor height, hob to extractor, etc, etc into account -
I’m coming close to the top of my external wall - maybe two courses down.

It’s a new soft red wall that non load bearing - there’s a stud wall inside.
Even done gently - I’m a bit concerned that the hole could blow / break open.

Do you have a rule of thumb on how close to top of wall it’s safe to core out a hole of this size.

Thanks D

We tend to stitch drill or purposely build-in a duct, when venturing towards the (weaker) top of the wall.

150mm with a drill will likely snatch and bind.

 

[Diggory]

Hi there - thanks replies.
It’s a single story extension to a bungalow - pitched roof.
It’s only now the kitchen plans have come together and we know where the hob centre line is.
I did think about building in a duct but I wasn’t confident enough on location.
It’s a bit of a challenge - I’m close to top of wall and even closer to soffit.

I’m now wondering about shooting it out vertically with insulated roof chimney.
Or, going for a 150 external housed fan further along the wall (away from hob) and lower.
Appreciate no grease filter in a ‘fan’ and I’ll likely have to clean it regularly or see it break.

Regards D

 

[thomp1983]

Is it a decorated wall?

If not I'd get a decent sized bit of 18mm osb or ply, cut your hole out of it then mount the board to the wall making sure to get screws in each block and the board will help hold it all together while you core.

Once you've cored 25mm or so into the material use a suitable length masonry bit to stitch drill around the hole a the way out through the brick work and then gently run the core drill through to cut the remaining bits.

 

[Murdochcat]

Drill from the inside to out as the softer breeze blocks will allow the core to establish a neat hole before hitting the bricks.

A proper core drill with a clutch and a decent diamond core drill are a must to get the job done - and don’t RUSH

 

[Diggory]

Thanks for drilling tips - the OSB frame sounds a good idea.
If I get the gist - consensus is that I could do it if I’m very careful.

Just to recap as some have asked questions about the wall…….
It’s a (new) single wall of ‘soft reds’ - I’d be coring out 160mm two courses down from top.
Inside is timber studding, infilled 75mm Celotex and over-boarded 40mm insulated plaster board.
It’s not decorated but it’s all plastered.

D

 

[Diggory]

One of my options - if I lose my nerve with the big ‘ole drill is an extractor fan.
Has anyone any experience of using a good fan instead of a cooker hood.
Not a cheapo bathroom one but a good quality 150mm centrifugal / capacity fan.
The obvious thing seems to be absence of any grease filter.
So I guess it would need a good clean a couple times year.

Any thoughts on this as a viable alternative.

D

 

[Murdochcat]

Are bco involved?

 

[Diggory]

BCO ?

 

[noseall]

One of my options - if I lose my nerve with the big ‘ole drill is an extractor fan.
Has anyone any experience of using a good fan instead of a cooker hood.
Not a cheapo bathroom one but a good quality 150mm centrifugal / capacity fan.
The obvious thing seems to be absence of any grease filter.
So I guess it would need a good clean a couple times year.

Any thoughts on this as a viable alternative.

D

If it's remote from the hob, it needs to run at 60 L/ps, if it's over the hob (cooker hood) it can be half that.

 

[noseall]

BCO ?

Building Control (officer).

 

[Diggory]

‘Are bco involved’

Yes - we are using a Registered Building Control Approver
I’m not getting the context of the are they involved question

 

[Diggory]

I’m guessing you mean - are BCO requirements behind me doing this.
No; I’m doing this because I want to get a decent extract from kitchen area.
I’ve got a ‘good brand’ but hopeless extractor now - and I want to make better job of it this time.
Plus, I’ve got more glazing now and more likelihood of condensation areas.

D

 

[jj4091]

Qwhat sort of extractor have you got that needs the hole to be drilled so high. Most chimney types would allow you to drill mich lower than that.