Core drilling / Kitchen exhaust installation / Execution evaluation

Dear community,

we have purchased a single-family house in which we had a new kitchen installed. On the recommendation of family members, we commissioned a contractor (with over 20 years of experience) who runs a home construction company (1 employee) with the following tasks:
- Core drilling for a 15 cm diameter exhaust vent of the kitchen extractor hood
- Construction of a drywall casing from the drilling to the extractor hood
including installation of the aluminum flexible duct (due to tight angles, a round or square duct was not possible)

Implementation:
The contractor drilled a hole with a diameter of 15 cm into the exterior wall. At that time, I was not aware of the size of the drilling. However, I had clearly stated that the exhaust should be 15 cm. When installing the wall box that I had procured, of course it did not fit because the core drilling should have been larger for this purpose. Therefore, it was switched to a 12.5 cm exhaust. Furthermore, I noticed that when laying the aluminum flexible duct, he simply stretched it apart, although the packaging clearly showed that the stretching should be done with a twisting motion so that it does not tear.
It must also be mentioned that he pierced a cable during the core drilling, although we had previously pointed out that a cable runs in the wall. We had the cable repaired by a friend who is an electrician.

After further work was not carried out properly (naively on our part we did not intervene at that time), we are now so upset that the following questions arise for the experts in this forum:

1) Do we have to accept the smaller core drill diameter? The extractor hood now has permanently less power because it can simply extract less due to the diameter of 12.5 cm (instead of 15 cm). Should something else have been communicated, e.g. "The exhaust system is to be operated with a 15 cm duct, i.e. the core drilling must be larger, according to the specifications of the wall box manufacturer"? I generally assume that a "construction professional" with years of experience knows that a larger drilling must be made than the diameter of the pipe!?

2) If the core drill was to be enlarged (which of course would now involve considerable effort as the kitchen is already installed), would that even be possible? If yes, how could that be practically carried out? Partially removing drywall? Taking down wall cabinets? Setting the core drill machine at hopefully the right height and angle and drilling through?

3) The installation of the casing profiles was well executed, but there are optical problems:
- the joint between 2 drywall panels is visible - I suspect that it was not properly filled and the filler was pulled into the gap
- in addition, there are grooves visible in parts of the casing - presumably caused by scraping with the trowel and then left as is
--> question see point 4)

4) Would a reduction of the service provided be justified based on the above points? Should one not even consider quantifying the damage incurred (pierced cable, reduced performance of the extractor hood) against the contractor?

Thank you in advance for the feedback and experiences. As can be seen, we had no experience, which is why we were "at the mercy" of the above procedure.

I am writing solely from a kitchen planning perspective:

Core drilling for a 15cm diameter exhaust vent of the kitchen hood

This should have included transmitting the planned wall box and its specifications. And not demanding a 15 cm diameter.

Regarding the flexible duct .. the planning should definitely have been revised or adjusted and the flexible duct should have been avoided.

If one wanted to enlarge the core drilling (which of course would now involve considerable effort, since the kitchen is already installed), would that even be possible?

Since we don’t know the location and the surroundings, how should one assess that?

commissioned with the following:
- Core drilling for a 15cm diameter exhaust vent of the kitchen extractor hood

Was a hole with 15cm commissioned or clearly communicated that the wall box has a 15cm diameter and must fit into a hole to be drilled?

But I clearly stated that the exhaust vent should be 15 cm. When installing the wall box I provided, it obviously didn’t fit because the core drill hole would have had to be bigger. Therefore, it was switched to a 12.5 cm exhaust vent.

Why? It would have been no problem to just enlarge the hole, right? So you accepted the 12.5 cm in agreement with the craftsman.

It should also be mentioned that during the core drilling he pierced a cable, even though it was previously pointed out that a cable runs in the wall.

What was the craftsman supposed to do? The cable does not just vanish into thin air.

We had the cable repaired by an electrician we know ourselves.

Why not by the craftsman? That must involve proper chasing and rewiring.

Furthermore, I noticed that when laying the aluminum flexible hose, he simply pulled it apart, even though the packaging clearly showed that the pulling apart should be done with a twisting motion so that it does not tear.

And? Did the hose tear or not? If not, you don’t have to worry about it.

Now a few sentences regarding your questions:
1: You already did that in agreement with the craftsman! You even procured a smaller wall box yourself.
2: Of course. Make space and drill again. Basically, the whole job all over again.
3: Unfortunately, I don’t see the problems. The pictures are not displayed for me, so I can’t comment on that.
4: I would talk to the craftsman. But charging for damage because of insufficient performance of the hood? I don’t see that. But I also can’t read the data of the hood. It’s not shown to me either.

125mm is too small for current range hoods. Yes, it works, but you lose the warranty because the wear is significantly higher. It is also probably much louder. If you order 150mm, you will get that. You should have acted when you noticed that the hole was too small. The cable would have been in this spot in any case. Or would you have preferred the hole to be moved? Then you would have had to inform the craftsman.

Good evening,

thank you very much for the feedback.

And I would like to respond as follows:

A drill hole commissioned with 15 cm or clearly communicated that the wall box has a 15 cm diameter and must fit into a hole to be drilled?

It was clearly stated what was planned. Of course, I did not say that I wanted a 15 cm hole, but that the exhaust air should be operated with a 15 cm pipe. By the way, the wall box was on hand. It was then immediately determined that the hole was too small. So the proper procedure would have been for me to read the package insert and tell him how big the hole should be (in this case at least 16.2 cm). Even with a diameter of 12.5 cm, a drilled hole of 15 cm is too big. In this respect, I see the 15 cm hole as professionally executed incorrectly. I would also like to point out that there is no wall box for a 15 cm drill hole, at least according to my research. At the time, I confronted the craftsman with this, reaction "Oh, I see."

Why? It would have been no problem to just enlarge the hole a bit? So you accepted the 12.5 cm in agreement with the craftsman.

This was not communicated to me as something that could just be done. On the contrary. Hence my inquiry here. Due to the pressure from the kitchen delivery, I agreed to take a wall box for a 12.5 cm exhaust. I now see that this was a mistake on my part! In a way, this can be interpreted as consent.

What should the craftsman have done? The cable does not just disappear into thin air.

It would have been possible to simply drill 1 cm further next to it, which I had pointed out.

Why not by the craftsman? That would require proper chasing and relaying.

Correct. It did not take place because the dude is not an electrician and I know one privately who took care of it – by the way, we did not receive any deduction on the invoice for this. In addition, there was time pressure due to the kitchen delivery.

Now a few sentences about your questions:

Thanks for the summary. Clear and precise. Great :)

125 mm is too small for current extractor hoods. Yes, it works, but you lose the warranty because the wear is significantly higher.

It is actually the case that the hood is approved for 12.5 or 15 cm. However, you also had to work with a reducing piece from the hood to the 12.5 cm hose. I think the warranty should be valid. But I do not know for sure.

Regarding the flexible hose ... the planning should definitely have been revised or adjusted and the flexible hose should have been omitted.

That would also have been very much appreciated by me, but unfortunately, it was not possible due to structural conditions.


Overall, many thanks for the helpful suggestions!

I would have liked that too, but unfortunately it was not possible due to the structural conditions.

I can hardly imagine that; perhaps a planning adjustment would have been sensible. In any case, the hood combined with only 12.5 cm of exhaust and flexible duct has a loss of performance.

By the way, the wall box was at hand.

Did you give it to the craftsman before drilling the hole?