ᐅ Bathroom drainage, number of downpipes, prefabricated wall systems, etc.

Good morning,

A stub gap = just a gap about 60 cm (24 inches) high, not room-high or spanning multiple floors.

By "real stone," we jokingly meant calcium silicate bricks – from a structural perspective, they cause the fewest problems. We had them installed everywhere, even on the upper floor.

Hello Sebastian,

Lexmaul79 schrieb:

What’s wrong with downpipes in the exterior wall? Especially structurally? That’s a gap of 15 (?) cm (6 inches) – which of course must be considered in the structural calculations.

The greatest demand on an exterior wall is load-bearing. Exterior walls also serve as the barrier between outside and inside, involving temperature differences. So, if you interrupt the wall—in your case, a relatively thin sand-lime brick wall—the structural carpenter usually has to reinforce this interruption with a reinforced concrete core. This also affects the calculations for thermal insulation verification. You are building a cavity wall; in the insulation layer, I personally would not want drainage pipes installed.

What I consider equally important is what happens if you need to access such a "hidden" pipe. Right—you have to open everything up again.

Lexmaul79 schrieb:

You can’t always drain or vent everything on the inside...

Any knowledgeable architect will recommend this option to you; boxed-in constructions are not so bad that they can’t be incorporated into the design.

Regards, Bauexperte

Bauexperte schrieb:
The biggest stress on an exterior wall is load-bearing. Exterior walls also serve as the barrier between outside and inside, especially regarding temperature differences. So, if you interrupt the wall—in your case a relatively thin sand-lime brick wall—the builder usually has to reinforce this interruption with a reinforced concrete core.

What do you mean by reinforced concrete core? I can’t imagine where you see something like that here. A sand-lime brick wall is load-bearing starting from 11.5cm (4.5 inches), and I don’t follow your argument—a window is also a weakening of a wall, as is a door. This is about a 15cm (6 inches) gap (not a chiseled-out wall), so the load does not need complex transfer.

Regarding temperature differences—you insulate the pipe and the gap again for that. Don’t forget that sand-lime brick is not an insulating material. It might be different with aerated concrete...

I actually happened to discuss this with the structural engineer and architect at the time.

Bauexperte schrieb:
That also changes the calculations for the thermal insulation certificate.

No, because the thermal insulation certificate is calculated with that in mind—normally nobody cuts such slots during the construction phase.

Bauexperte schrieb:
You’re building double-shell; I personally wouldn’t want drainage installed inside the insulation.

It’s not inside the insulation but in front of it. Personally, I don’t see a problem there.

Bauexperte schrieb:
What I also consider important is what happens if you need to access that "hidden" pipe. Right—you have to open everything again.

What do you mean by “everything”? I would just chisel open the gap covered with expanded metal lath, insulation, and plaster, and that would give me access. The boxing around the pipe would also have to be opened. Sure, there is a bit more mess with my solution, but the effort is not fundamentally different.

Bauexperte schrieb:
Any sensible architect will recommend this option; pipe boxing is not so bad that it can’t be integrated aesthetically.

I consider my architect and builder quite smart and experienced (so no need to disparage them). Installing a pipe chase or boxing outside the exterior walls would not have been possible—or do you want the pipes running down/up in the middle of the room?

Some might not care, but we do.

It’s just not to your taste, but technically I don’t really see a valid objection against it from your side.

Lexmaul79 schrieb:

What do you mean by reinforced concrete core?

I assume that if the wall is interrupted, this weakening of the external wall must be compensated.

Lexmaul79 schrieb:

- a window is also a weakening of a wall, as is a door.

So, you don’t use lintels in the house?

Lexmaul79 schrieb:

No, because the thermal insulation verification was calculated accordingly – normally no one makes such openings during the construction phase.

Of course, this was calculated and “taken into account” before construction started.

Lexmaul79 schrieb:

I consider my architect and the shell builder quite smart and experienced (so you don’t need to belittle them) – boxing or routing outside the external walls wouldn’t have been possible – or should the pipes run up/down in the middle of the room?

It’s interesting – you rarely hold back your opinion, but when it goes the other way, you accuse others of “belittling”?

For your information: there are architects who always choose the path of least resistance. Whether this is in the best interest of their clients is up for someone else to decide.

Lexmaul79 schrieb:

It’s just not your preference, but technically I can’t really find anything against it from your side…

This has little to do with “preference”; I primarily consider the accompanying circumstances. Our architects would only agree to drainage in the external wall if there was no other way to redirect the water.

This is not about criticizing your work, just about pointing out the surrounding conditions.

Best regards, Bauexperte

You are making assumptions, but there is no compensation...

I already understood what you meant – and that’s how I responded. And you keep making assumptions... just so you know: it was not part of our contract that we did not want any boxing-in. But we simply like it the way it was executed.

I wouldn’t care whether you put it down or not – you are not an expert in structural engineering or thermal insulation, but of course you have an opinion, as do I. And when two "experts" explain it to me, as I already suspected, I tend to think they are not entirely wrong.

This was only about how things are usually done – and that’s all I described.

In our case, there were no issues with the structural stability or heat loss. Concrete was also not used in our walls.