Why are soil pipes run internally?

[saveasteading]

You're right. Buildings vary. A big block of flats of offices will likely have a service shaft for supplies in and waste out. With floors it can readily be serviced, the noise doesn't matter, and any leaks are relatively harmless.

Unfortunately they create a fire risk when stops are omitted.

 

I'm a philistine according to some architects. My design priority is to keep the weather out. Otherwise what is the building for?

I don't like flat roofs or internal gutters.

 

The liabilities if a roof leaks are potentially huge, and any professionals  involved could be in trouble.

The calculations for gutters and drains are not easy, then build quality needs attention.

 

A diversion:  prior to raac panels becoming a well known problem, there was strawboard. It also fails when wet, but really only when flat roofs or internal drains fail.

[Alan Ambrose]

Well I agree with you for domestic. While the look of no pipes is good, anything buried in a wall or floor is a potential maintenance headache.

[Mike]

7 hours ago, Crofter said:

I found it hard to imagine that a single toilet could generate so much of a vacuum that it needed a 110mm vent.

I used a 50mm pipe instead, which meant I could run it hidden behind the larch cladding.

If you're no more than 2 floors high, a 75mm vent is fine under English building regs.

[Crofter]

1 hour ago, Mike said:

If you're no more than 2 floors high, a 75mm vent is fine under English building regs.

I'm not aware of Scottish regs allowing for anything other than 110mm.

It seemed complete overkill for a single toilet on the ground floor.

[saveasteading]

20 minutes ago, Crofter said:

complete overkill for a single toilet on the ground floor

I'm sure you could debate with the bco or provide calculations to justify 50 or 75mm  when it's simple, but just use 110 unless there is an important reason. Isn't it cheaper in 110 esp at junctions?

[Crofter]

55 minutes ago, saveasteading said:

I'm sure you could debate with the bco or provide calculations to justify 50 or 75mm  when it's simple, but just use 110 unless there is an important reason. Isn't it cheaper in 110 esp at junctions?

It wasn't a cost decision, although the 50mm solvent weld that I used is really cheap too.

The decision behind it was that I could run the SVP up the outside wall within the depth of the battens for the timber cladding. Means it's completely hidden from view yet external to the house in case of any leaks, and no AAV needed.