ᐅ Drilling into the exterior wall on the upper floor; creating an opening is not possible.
Created on: 28 Apr 2026 18:00
S
scramerHello everyone,
As a longtime reader, I now have a problem/question of my own.
I am planning to install an air conditioning unit for the children’s floor (upper floor) of my house. Apart from connecting the unit, I want to do all the work myself for cost reasons. However, I’m encountering some real resistance when preparing for the core hole drilling.
The children’s floor is on the upper floor of a house built in 1970. The exterior walls are 24 cm (9.5 inches) thick, probably made of sand-lime brick or possibly pumice blocks(?). The drilling is supposed to be done in one of the rooms just above the floor level. The reason is that a conservatory was added later on, and the pitched roof almost rests on it. Although there is quite a large gap between the flat roof of the conservatory and the pitched roof (I estimate about 30-40 cm (12-16 inches)), working from outside is not possible because the roof almost touches the wall (unless I open the roof there, which I’d prefer to avoid).
To check if I can reach the space above the flat roof from inside, I first drilled with a hammer drill at a downward angle towards the outside. The wall is 24 cm (9.5 inches) thick, presumably sand-lime brick? The drilling dust is gray or white. I managed to drill about 20 cm (8 inches) quite well—first with a smaller drill bit, then gradually with larger ones. But after those 20 cm, I can’t get any further. I initially used cheap SDS drill bits from the hardware store. After burning out one bit and chipping the edge off another, I switched to a better quality bit (not professional Bosch, but close). Still, it won’t penetrate the stone any further, and if I apply pressure, the hammer drill’s clutch slips.
Before I tackle the core drilling tomorrow, I’d like to first complete the normal drilling. I welcome any guesses or explanations why it’s not working. I can’t really see any steel reinforcement through the hole (the drill bit is still quite small despite being 20 mm (0.8 inch)), but were ring beams already used in the 1970s? Still, the “better” drill bit should be able to get through, right? I’m a bit frustrated right now. The installer is coming next week, and I need to get the breakthrough done.
I’m grateful for any tips!
Relocating the drilling position is rather inconvenient. There are still two heating pipes (supply and return) running through the wall, so space is limited. Raising the hole significantly is unfortunately not really possible.
As a longtime reader, I now have a problem/question of my own.
I am planning to install an air conditioning unit for the children’s floor (upper floor) of my house. Apart from connecting the unit, I want to do all the work myself for cost reasons. However, I’m encountering some real resistance when preparing for the core hole drilling.
The children’s floor is on the upper floor of a house built in 1970. The exterior walls are 24 cm (9.5 inches) thick, probably made of sand-lime brick or possibly pumice blocks(?). The drilling is supposed to be done in one of the rooms just above the floor level. The reason is that a conservatory was added later on, and the pitched roof almost rests on it. Although there is quite a large gap between the flat roof of the conservatory and the pitched roof (I estimate about 30-40 cm (12-16 inches)), working from outside is not possible because the roof almost touches the wall (unless I open the roof there, which I’d prefer to avoid).
To check if I can reach the space above the flat roof from inside, I first drilled with a hammer drill at a downward angle towards the outside. The wall is 24 cm (9.5 inches) thick, presumably sand-lime brick? The drilling dust is gray or white. I managed to drill about 20 cm (8 inches) quite well—first with a smaller drill bit, then gradually with larger ones. But after those 20 cm, I can’t get any further. I initially used cheap SDS drill bits from the hardware store. After burning out one bit and chipping the edge off another, I switched to a better quality bit (not professional Bosch, but close). Still, it won’t penetrate the stone any further, and if I apply pressure, the hammer drill’s clutch slips.
Before I tackle the core drilling tomorrow, I’d like to first complete the normal drilling. I welcome any guesses or explanations why it’s not working. I can’t really see any steel reinforcement through the hole (the drill bit is still quite small despite being 20 mm (0.8 inch)), but were ring beams already used in the 1970s? Still, the “better” drill bit should be able to get through, right? I’m a bit frustrated right now. The installer is coming next week, and I need to get the breakthrough done.
I’m grateful for any tips!
Relocating the drilling position is rather inconvenient. There are still two heating pipes (supply and return) running through the wall, so space is limited. Raising the hole significantly is unfortunately not really possible.
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