Drilling hole under supporting beam

[Kraggash]

We moved into a house with a cooker extractor hood set up to 'recirculate' which noisy, and ineffective. I would like to convert to external extraction, which, as its on an external wall, should be reasonably simple.

However, the hood is mounted directly beneath a large supporting beam from where a wall was removed. I am worried that drilling a 150mm hole here might weaken the wall too much: maybe why that's why it was not done before? Anyhow, I was looking for advice on whether the idea was possible or not. How close to the beam would a 150mm hole (100mm hole at a push, I guess) would be minimum safe distance?

House is 1920's build, kitchen last done about 12 years ago, ceiling is 2.7m high. Beam (boxed in) is 290mm high. Bottom of beam box is 280mm above top of existing fan, inside hood. I assume there is a pad stone, but it's behind plasterboard.

Any advice welcomed.

 

[jeds]

If there's a 400mm padstone (estimate based on width of beam?) and the masonry is good, a 150mm hole, say, 150mm-200mm below the padstone will have little effect on the bearing. At some point your going to need to have a look though. Maybe start a hole 150 below and see if you can see the bearing?

 

[Kraggash]

If there's a 400mm padstone (estimate based on width of beam?) and the masonry is good, a 150mm hole, say, 150mm-200mm below the padstone will have little effect on the bearing. At some point your going to need to have a look though. Maybe start a hole 150 below and see if you can see the bearing?

Thanks. Yes, I started to poke around then realised I'd have have to take off the cooker hood, then make a hole though the plasterboard (which appears to be attached using studs) before I could even see the wall. Messy. I would like to know what to look for, or if its even possible, before I start.

150mm below padstone doesn't leave a lot of room for a right angle duct piece and a 150mm hole above the fan body. (I know there are ones with lower fans though).

 

[cdbe]

You might be able to run a duct up to the right of the beam and box it in.

 

[Tigercubrider]

First thing is to remove the chimney part to expose the motor so you can see your venting options.
Be careful as I managed to punch a hole in my floor by letting the lower part of my chimney slip out as I moved it.
Given that it's a short run you might get away with a smaller hole? Each bend also slows down /affects the flow.
If the unit is reasonably new, are there alternative chimneys that would offer options?

 

[Kraggash]

First thing is to remove the chimney part to expose the motor so you can see your venting options.
Be careful as I managed to punch a hole in my floor by letting the lower part of my chimney slip out as I moved it.
Given that it's a short run you might get away with a smaller hole? Each bend also slows down /affects the flow.
If the unit is reasonably new, are there alternative chimneys that would offer options?

Yup, done that. There is just a round attachment point, with butterfly valve, ready for ducting, at the top of the fan motor. As I said, this is 280mm below the boxing for the beam. All I need is a 90 degree trunking piece, and a straight section and I am through the wall and out. 100mm would be better than recirculating, I guess, although 150mm 'strongly recommended'.

 

[Kraggash]

'Common sense' (I.e. guesswork) would suggest there would be triangular no-drill area beneath the beam, with the base of the triangle being the beam width. Anybody know if this is true, and what angles should be used?

 

[jeds]

Depends on the length of the pad stone?