Soil stack airtightness

[Selfbuildsarah]

Our timber frame is nearly up and we have a roofer and builder lined up for external work. I don’t think our roofer is familiar with airtight, timber frame or our builder 😬 We have been advised to use ProClima Roflex gasket and Tescon Vana tape to seal soil stack. Apologies if this is a silly question (mine usually are) but is this for penetration through the roof tiles or lower or both? Should we also be using a special flashing? Our roofing will be Danum TLE system. We are going to have to explain this clearly to roofer and builder this morning!

[Bramco]

Would it be possible to run a soil stack up the side of the house? We did this to avoid having a penetration through the roof.

 

All internal soil locations have air vents. The external one runs vertically parallel to a downpipe, so isn't too out of place. It connects to the sump where all the internal ones come together.

[Selfbuildsarah]

Thanks Branco. We did think about this. We will have a further chat with builder this morning.

Presumably we will have to get the OK with building control first if we choose to do that?

Edited 14 hours ago by Selfbuildsarah
Omission

[Russell griffiths]

Where is your technical drawing showing the location of your airtight layer. 
is it showing the vcl at ceiling level or roof level. 
you need to imagine and show the roofer/ builder an image of a continuous line around the whole property with no gaps or breaks in it. 
from ground floor to roofline a continuous air barrier. 

[Selfbuildsarah]

Just spoken to Brendan from MBC on site and he’s reassured us all taping including soil pipe will be done by MBC so we will stick with the one plus AAVs 👍

[Selfbuildsarah]

Building control have just said fit an in-line roof tile vent. Opinions please!

[Mr Punter]

With the roof tile vent you don't need flashings but you need the right vent for your tiles.  They have a flexi connector.

[Bramco]

6 hours ago, Selfbuildsarah said:

Thanks Branco. We did think about this. We will have a further chat with builder this morning.

Presumably we will have to get the OK with building control first if we choose to do that?

Building control actually came up with the solution!!

[Bramco]

3 hours ago, Selfbuildsarah said:

Just spoken to Brendan from MBC on site and he’s reassured us all taping including soil pipe will be done by MBC so we will stick with the one plus AAVs 👍

I should have said ours was an MBC build. But we'd already decided we didn't like/trust the idea of a soil pipe through the roof structure. Getting the taping right on 2 membranes at an angle seemed like a recipe for future problems.

[Nickfromwales]

44 minutes ago, Bramco said:

I should have said ours was an MBC build. But we'd already decided we didn't like/trust the idea of a soil pipe through the roof structure. Getting the taping right on 2 membranes at an angle seemed like a recipe for future problems.

Not an issue tbh.

 

 

 

 

 

I taped and foamed these to within an inch of their lives. Airtightness score was 0.1ACH on test, so a safe 0.2ACH which I will take allllllll day long.

 

It’s not what you have to tape, it’s who you’ve got, or knowledge and methodology if DIY’ing.

[Dunc]

Another MBC build here. No soil stack through the roof (have a separate branch outside to do the venting bit and an air admittance valve at the top of the stack internally to do the anti-vacuum bit. Is that an option for you?). However, as Nick above, we have MVHR ducts and terminals penetrating the inside membrane in the upstairs ceiling (i.e. the airtight layer). Brendan taped them all up no problem at all and the building achieved 0.3 ACH. On that basis all you would need to worry about is your roofer getting a watertight (rather than airtight) seal on the outisde.

[Russdl]

15 hours ago, Selfbuildsarah said:

I don’t think our roofer is familiar with airtight, timber frame

As you’re with MBC I guess you’re going passive-ish?

 

If you are (and you should, especially if you’re using MBC) don't put anything through the roof, even if the soil stack is effectively sealed it’ll be an unnecessary thermal bridge. 
 

As @Dunc says:

 

4 hours ago, Dunc said:

No soil stack through the roof (have a separate branch outside to do the venting bit and an air admittance valve at the top of the stack internally to do the anti-vacuum bit

That is the way to do it. That’s the way we did it. 
 

MBC will do what you ask, and do it well and the airtightness will be spot on, but if you’re trying to be ‘passive’ don’t have that tube going through the roof. 
 

Also, don’t put any ducting through the insulation if you can possibly avoid it (you can).

 

Any large ducts through the insulation will degrade the insulation properties where the ducts are, and that’ll degrade the ‘passive’ aspect, the passive bit is worth fighting for, it pays dividends. 
 

There is always a better way so that you can keep everything inside the airtight layer, even if it may compromise a little bit of the interior space.