Extract fan recomendation

[Mike Johnson]

Remove the pilot drill once you have about 25mm drilled into the wall to act as a guide.

Nor do I?

Six inch holes are fun.

 

[Mikegh]

I'll retype that

Also seen something about drilling pilot holes to reduce dust but didn't quite get that idea ?

 

[brianmoooore]

Joists in an old building probably have herringbone strutting between the joist.

Appropriate length of 3 X 2 and a large hammer will deal with these. Many have met their end this way by myself and my trusty 4lb lump.

 

[Mike Johnson]

That strutting is just there for decoration, and don't forget to drill holes wherever you want in the joist while your at it.

 

[brianmoooore]

Buildings like this tend to be somewhat over engineered by modern standards, and built with nice close grained timber, not the modern stuff with rings a cm apart. Removal of a strut or two isn't going to cause any movement.

 

[Mike Johnson]

Until the next person comes along and thinks exactly the same.

 

[Mike Johnson]

I'll retype that

Also seen something about drilling pilot holes to reduce dust but didn't quite get that idea ?

May be alluding to drilling all around the outside of a large diameter hole instead of diamond drilling, there is no doubt that diamond drilling does cause a lot of dust, but you do get a neat hole that requires very little finishing, even through plaster, and outside just a neat hole to put the cowl in.

 

[littlespark]

My last core was through 800mm of rubble built solid stone walls.

Once you’ve drilled through with just a long 10mm bit or whatever, start off the core using the pilot… will keep it straight following the first hole.
You’ll need a few inches cut with core before you can dispense with the pilot and let the core follow its own path.

There was a section where the rubble would drop into the new hole. I just had to clear it frequently.

Hire a drill and core if you can. Saves burning out your own machine, and keep a tight hold of the drill!

 

[Mike Johnson]

As both I and @littlespark have said keep hold of the drill using the side screw on arm, I have seen broken wrists through the core jamming and the drill not having a clutch, I had my own Marcrist set, about the best dry core bits you can get without spending mega money.

 

[Mikegh]

I'd get the core drill
I suppose the best thing with the ducting is go to the builders merchant .
I usually end up getting parts that don't fit together.