ᐅ Core Drilling / Installation of Kitchen Ventilation / Assessment of Workmanship
Created on: 29 Jun 2025 17:50
M
Mike_Ef
Dear community,
We have purchased a single-family house in which we had a new kitchen installed. Based on a family recommendation, we hired a contractor (with over 20 years of experience) who runs a home construction company (1 employee) to do the following:
- Core drilling for a 15 cm (6 inch) diameter exhaust duct for the kitchen range hood
- Construction of a drywall enclosure from the drill hole to the range hood
including installation of the aluminum flexible duct (due to tight angles, a round or square rigid duct was not possible)
Implementation:
The contractor drilled a 15 cm (6 inch) diameter hole through the exterior wall. At that time, I was not aware of the exact size of the hole. However, I clearly communicated that the exhaust duct should be 15 cm (6 inches). When installing the wall box I had provided, it obviously did not fit because the core drill hole would have needed to be larger. Therefore, the project was changed to a 12.5 cm (5 inch) exhaust duct. I also noticed that when laying the aluminum flexible duct, he simply stretched it apart, although the packaging clearly showed it should be stretched while rotating to avoid tearing.
It must also be mentioned that during the core drilling he damaged a cable, even though he had been warned beforehand that a cable runs inside the wall. We had the cable repaired ourselves by a known electrician.
Since (naively on our part without intervening) further work was not done properly, we are now so frustrated that the following questions arise for the experts in this forum:
1) Do we have to accept the smaller core drill diameter? The range hood now permanently operates with less power because it can simply exhaust less air due to the 12.5 cm (5 inch) diameter instead of 15 cm (6 inch). Should something else have been communicated, for example: “The exhaust system must be operated with a 15 cm (6 inch) duct, meaning the core drill hole must be larger accordingly, as specified by the wall box manufacturer”? I generally assume that a “building professional” with many years of experience knows that the drill hole must be larger than the duct diameter!?
2) If we wanted to enlarge the core drill hole (which of course would now involve significant effort since the kitchen is already installed), would that even be possible? If so, how could that be practically done? Remove part of the drywall? Take down the wall cabinets? Position the core drilling machine at hopefully the correct height and angle and drill through again?
3) The installation of the profiles for the enclosure was done well, but there are visual issues:
- The joint between two drywall panels is visible – I suspect the joint compound was not applied properly and was pulled into the gap
- Additionally, there are grooves visible in parts of the enclosure – likely caused by trowel marks that were left unfinished
--> See question 4)
4) Given the above points, would a reduction in the paid service be justified? Should we even consider quantifying the damages (damaged cable, reduced performance of the range hood) against the contractor?
Thank you in advance for your feedback and experience. As you can see, we had no previous experience and were therefore “at the mercy” of the above approach.
We have purchased a single-family house in which we had a new kitchen installed. Based on a family recommendation, we hired a contractor (with over 20 years of experience) who runs a home construction company (1 employee) to do the following:
- Core drilling for a 15 cm (6 inch) diameter exhaust duct for the kitchen range hood
- Construction of a drywall enclosure from the drill hole to the range hood
including installation of the aluminum flexible duct (due to tight angles, a round or square rigid duct was not possible)
Implementation:
The contractor drilled a 15 cm (6 inch) diameter hole through the exterior wall. At that time, I was not aware of the exact size of the hole. However, I clearly communicated that the exhaust duct should be 15 cm (6 inches). When installing the wall box I had provided, it obviously did not fit because the core drill hole would have needed to be larger. Therefore, the project was changed to a 12.5 cm (5 inch) exhaust duct. I also noticed that when laying the aluminum flexible duct, he simply stretched it apart, although the packaging clearly showed it should be stretched while rotating to avoid tearing.
It must also be mentioned that during the core drilling he damaged a cable, even though he had been warned beforehand that a cable runs inside the wall. We had the cable repaired ourselves by a known electrician.
Since (naively on our part without intervening) further work was not done properly, we are now so frustrated that the following questions arise for the experts in this forum:
1) Do we have to accept the smaller core drill diameter? The range hood now permanently operates with less power because it can simply exhaust less air due to the 12.5 cm (5 inch) diameter instead of 15 cm (6 inch). Should something else have been communicated, for example: “The exhaust system must be operated with a 15 cm (6 inch) duct, meaning the core drill hole must be larger accordingly, as specified by the wall box manufacturer”? I generally assume that a “building professional” with many years of experience knows that the drill hole must be larger than the duct diameter!?
2) If we wanted to enlarge the core drill hole (which of course would now involve significant effort since the kitchen is already installed), would that even be possible? If so, how could that be practically done? Remove part of the drywall? Take down the wall cabinets? Position the core drilling machine at hopefully the correct height and angle and drill through again?
3) The installation of the profiles for the enclosure was done well, but there are visual issues:
- The joint between two drywall panels is visible – I suspect the joint compound was not applied properly and was pulled into the gap
- Additionally, there are grooves visible in parts of the enclosure – likely caused by trowel marks that were left unfinished
--> See question 4)
4) Given the above points, would a reduction in the paid service be justified? Should we even consider quantifying the damages (damaged cable, reduced performance of the range hood) against the contractor?
Thank you in advance for your feedback and experience. As you can see, we had no previous experience and were therefore “at the mercy” of the above approach.
N
nordanney3 Jul 2025 22:37Mike_Ef schrieb:
Obviously, I didn’t say I wanted a 15cm (6 inches) hole, but that the exhaust system should be installed using a 15cm (6 inches) duct. By the way, the wall box was available. Okay. So the mistake was on the contractor’s side – they also had the wall box?
Mike_Ef schrieb:
It would have been possible to drill just 1cm (0.4 inches) to the side, which I had pointed out. So it was clear down to the centimeter where the cable runs, and the contractor was aware of it? With the 180mm (7 inches) duct, they would have had even more problems and would have had to move the core drill hole much further. Would that have worked?
Mike_Ef schrieb:
It’s actually true that the hood is approved for 12.5 or 15cm (5 or 6 inches). So you have (unfortunately) an exhaust system that fits the hood exactly.
What I would do? Talk to the contractor and ask what kind of compensation they are offering. Although you don’t really have any real damage (unless you couldn’t return the wrong wall box), since the exhaust fits the hood. Maybe even with the same airflow performance as with the 150mm (6 inches) duct.
Don’t worry too much. Sometimes you just have to chalk things up to bad luck. Look forward to your new house and kitchen instead.
T
Teimo19884 Jul 2025 17:39I made core drill holes using a 152 mm (6 inch) hole saw and was able to easily pass the 150 mm (6 inch) pipe through. Obviously, with a 150 mm (6 inch) hole, it gets a bit tighter, but I can imagine you could get it through using Vaseline or something similar. If you ever feel like swapping it out later, that's possible. Just keep in mind that my pipe measurements refer to the outside diameter.
kbt09 schrieb:
I can hardly imagine that; perhaps a design adjustment would have been sensible. Due to the structural conditions, it wasn’t possible to run the cable through the wall along the ceiling, so the hole had to be made about 15–20 cm (6–8 inches) below the ceiling. This means two angles would have been needed, which probably would have meant going deeper than the mentioned 15–20 cm (6–8 inches), at least that is how the kitchen planner explained it. If there was a way to solve it differently, then the information or advice given was probably incorrect.
kbt09 schrieb:
Did you give that to the tradesperson before drilling the hole? nordanney schrieb:
Did they also have the wall box? If I remember correctly, no. So the responsibility likely lies with me. However—please don’t take it the wrong way—I would have expected the professional to ask me about it.
nordanney schrieb:
So it was clear down to the exact centimeter where the cable runs, and the tradesperson was also informed? Yes. But he didn’t want to accept that. In hindsight, I should have stopped the whole process at that point...
nordanney schrieb:
What I would do? Talk to him and demand compensation. That’s exactly how we plan to proceed.
nordanney schrieb:
Don’t worry too much. You just have to chalk many things up to bad luck. Look forward to the house and the kitchen instead. Thank you 🙂 I’ve gained some experience and now know that clear communication about what exactly should be implemented is important.
Teimo1988 schrieb:
If you ever feel like swapping that later I will definitely swap it once the other “construction sites” are finished. Maybe I’ll even buy some petroleum jelly for it 😉
Many thanks for all the feedback. I found it very helpful. Best regards to everyone!