Internal soil stack - box in, or put within stud wall?

[Scarlett B]

First time poster with limited plumbing experience - go easy on me
We're doing a loft extension, and will have an internal soil stack serving a ground floor, first floor, and loft toilet - the 3 toilets are pretty well aligned. The soil stack will be 'boxed in' on the ground floor and first floor.

Should we:
A. Also 'box in' the soil stack in the loft, as it travels to vent to the roof? The problem is this box would be in an ugly position in the loft shower-room. We want to avoid this option if possible.
B. Hide the soil stack within the stud wall in the loft, as it travels to vent to the roof? This stud wall is being built as part of the loft extension. The stud wall could be made wider than usual (20, 25, even 30cm) to accommodate the soil stack, and would not compromise the appearance of the loft shower-room (it is nice and wide, so we don't mind losing some width). This is our preferred option. However, we've heard the noise from the soil stack might then transmit around the house - is this a big problem, and can this be avoided with good insulation, or even boxing it in within the stud wall etc?
C. Rather than venting to the roof, vent to the loft shower room using a Durgo/AAV? I'm not sure this would look any better than option A. Plus I don't like the idea of having three toilets venting to an internal space!

We will have a builder and plumber helping us, but having advice will help us plan at this stage. Any advice much appreciated!! Thanks

 

[sxturbo]

DO NOT go the durgo valve route, you will have problems later on

rather than vent through the roof, why not go out the side of the wall, cut the pipe down low, you can then box in the pipe nice and low into an s-bend out the wall and up on the side of the house (if this is possible)

 

[Scarlett B]

Thanks for the reply sxturbo.

Ok, thanks, wlll avoid the Durgo valve route (although note that even Options A and B may require an external Durgo, since close to velux windows - I hope that is less problematic...)

Re going out the side of the wall - good idea, but unfortunately this doesn't work with the layout of our house (semi-detached house, position of toilets means cannot go out side of the wall).

Did you have any thoughts on Option B? (our preferred option)

 

[sxturbo]

Option b is fine, stud it decently and fill it with insulation.if any pipework is to be there then make sure you factor in inspection doors.

Regarding the Durgo, do whatever you can to avoid it, it will cause you more problems than it's worth.

 

[Hugh Jaleak]

Option B is fine, provide some access to the WC connection, but anything above that, (the 'dry' section, which is purely venting), can be boxed in, insulate for sound deadening. As above I advise you do not use an AAV (Durgo), having gone that far up, vent it through the roof. Allows the system to breathe, and prevents any later issues with a stuck open AAV stinking the loft out, or traps being pulled/blown if other issues arise.