Can a hole for ducting be cut through the wall at an angle?

[mithrand]

My kitchen fitter has discovered a problem while measuring up to fit our chimney extractor hood, being fitted into a single storey extension. In order for the hood to be at the minimum height above the oven, the hole for the ducting is going to be too high to clear the soffits on the outside. He wants to cut a 120mm hole, and even at the lowest he can get away with, the centre hole will (he estimates) be at the same height as the soffit.

Could he cut the hole at an angle, so that the exterior hole is (at least) 60mm lower than the interior hole? I would guess he was going to use a core drill - can that cut at an incline or must it go through horizontally? The wall is (as far as I can tell) a standard cavity wall with blocks on the inside and red bricks on the outside.

I guess I also don't know if there are regulations to do with angles of ducting, cutting holes etc. besides the practicality of cutting a big hole at an angle. I've asked him to have a chat with the builder about it - but I wonder if I'm asking him to do an impossible task!

But anything that could be done to avoid going down the recirculation route (their suggested solution) I'd like to investigate... since I would prefer not to risk any condensation / moisture problems. It's an extractor for a 100cm range cooker so I'd imagine it has the potential of causing a world of problems if not externally vented...

Or maybe there's another trick to getting around this problem? I can't be the only one who has discovered soffits that are lower than the internal walls...

Edit: I should add that there's no access to the roof space, so I don't think ducting up through that space is an option.

 

[hotrod]

I wouldn't recommend core drilling at a significant angle. I can't understand why the builder is having such a problem to be honest.

Isn't the hood telescopic? What is the make and model of hood and what is your floor to ceiling height?

 

[Timbobalob]

Can you go higher into the soffit and do a 90 deg bend to vent down?

You'll need long and bendy arms to do this however...

 

[chappers]

cut a hole up through the ceiling , within the chimney, run the ducting down between the rafters and vent it through the soffit, reduce the ducting down to 100mm to give you a better chance of missing the ceiling ties.
Or use a tile/slate vent.

 

[JohnD]

I can't see why he shouldn't drill it at an angle. Sloping down towards the outside is much better than the other way as it will prevent water running into the house. He will have to drill from the outside. If it was me I would drill the pilot first so I could confirm positioning was OK. The external cowl socket will have to be trimmed as it will not fit the elliptical duct end.

recirculating fans are absolutely useless, except as ornaments.


p.s. or you could shorten the "chimney" of the hood as it is probably not functional

 

[noseall]

Go through the roof via a tile vent terminal (tvt).

Cutting masonry so close to the soffit is not a good idea as you may disturb more bricks/blocks than you want to, being close to the final courses.

 

[JohnD]

can you show us a photo of the hood, from the back (wall) side?

 

[Nige F]

My kitchen fitter has discovered a problem while measuring up to fit our chimney extractor hood, being fitted into a single storey extension. In order for the hood to be at the minimum height above the oven, Edit: I should add that there's no access to the roof space, so I don't think ducting up through that space is an option.

Pitched roof - there`s access through the tiles , and a lead slate fitted round the pipe penetrating the roof - or a ubink ? vent tile Biggest problem will be finding a competent "roofer" @ a sensible price

 

[mithrand]

Sorry for not replying sooner - been a bit manic!

He figured it out, and it is now venting out of circular ducting. Apparently went to see some people who know ducting, and got some extra parts. He didn't elaborate on what he did to make it work Would have loved to know if he went for drilling at an angle. I googled for a while but couldn't find any comments for or against.

The problem was that even though the chimney was height adjustable, even at the minimum height up the wall (to give clearance to the hob) the vent was going to be close to soffit height. Floor to ceiling (inside) is 224cm, with the soffits outside about 20cm lower than the ceiling.

I got the impression neither he nor the builder wanted to start cutting into the roof / ceiling / soffits. I guess that was always possible but would involve more time and risk.

Thanks for the replies - I do appreciate it.