Soil pipe through foundations

mbguid · 1 Nov 2010

I'm building a largish extension which will have a new soil pipe which must pass through the new foundations. Building regs say that this should pass through a duct which should be sealed with foam and the ends covered with sheet material, I think to keep out vermin and stop the infill from filling the gap between the pipe and the duct. I understand all of that but don't know what the best sheet material would be. It obviously needs not to rot underground or be susceptible to vermin attack.

This must be something that builders use every day, so what's the best material?

Many thanks,

Mike.

noseall · 1 Nov 2010

18mm shutter ply.

mbguid · 2 Nov 2010

noseall said:
18mm shutter ply.

Surely that will only last a few years underground?

Mike.

marshman · 2 Nov 2010

Your soil pipe should be bedded on 50 mm of pea shingle, it should be covered over and all round with 50 mm minimum of pea shingle,
if you use a 150 mm pipe as your duct, plug each end both side of your footing trench then back fill over the ends with shingle,
the sheet or ply is stood up the sides of your footing trench to stop the concrete running out down your drain trench,
depending on the width of your drain trench or the order that you are doing things you put in temporary props to hold the ply in place
and back fill your drains, remove props as concrete level holds ply in place, remove ply next day, or forget its down there.

mbguid · 3 Nov 2010

Thanks Marshman for a useful explanation. However, that is not what the regulations require. Diagram 7 in H1 of the drainage regs says that the sheet material is there is keep the fill and vermin out of the duct through the foundations. That is because any differential settlement between the foundations and the pipe will put pressure on the pipe if the duct is full of incompressible material. They want the 50mm gap between the pipe and the duct filled with compressible material to exclude gasses and the fill.

So my original question still stands I think.

thanks,

Mike.

Static · 3 Nov 2010

I think your trying to combine two different methods.. here:

View media item 22047
Good ol NHBC show a couple of diagrams..
Doing compressible fill around the pipe and capping the ends seems an overkill and can be argued that the compressible material is sufficient to stop rodents..

mbguid · 3 Nov 2010

Untitled

mbguid
3 Nov 2010
2

This is the picture from the regs. I don't think I'm trying to combine the two methods.

Mike.

theoldun · 3 Nov 2010

Mike, With due respect you are at six’s and sevens here.
Your drawing is taken from Building Regs Part H 2.24b showing drainage through brick footings
Statics drawing is taken from NHBC Good Craftsmanship Guide showing drainage through foundations.
You have two different animals here.
Now you state that your drainage is coming through your foundations which is the concrete as Static shows. Then you have your brick footings which your drawing shows.
If you have a 1050 dig and 750 concrete fill, this leaves you 6 course of brickwork to DPC and 4 course to ground level. Nine times out of ten you can get out through your brick footings if you take a 200 to 300 deep by 450 wide pocket out of foundation concrete when it has addled of.
We work our inverts out before we pour and then we know whether we are coming out through founds or footings.
Coming out through founds is a completely different and awkward ball game.
If you don’t understand what I have wrote, come back and will explain more.
How ever, as noseall stated, 18mm ply is common practice in most situations..
oldun

theoldun · 3 Nov 2010

Deleted

mbguid · 3 Nov 2010

I know I'm being picky, but I just want to understand clearly what the regs say and how to implement them. You are right that the diagram I posted comes from BR H, section 2.24. However, that says "... at any points where pipes are built into a structure, including ... footing ... or wall" then you need to take those measures, either using a duct as per the diagram I posted or using rocker pipes. The regs do not make a difference between going through a wall or going through the foundation and that at least makes sense.

I am sure that you are absolutely correct in pointing out that 18mm ply is commonly used and I imagine that in the real world that's absolutely OK as you won't likely get vermin tunnelling through the pea shingle and through the foam or whatever "compressible material" you lined the duct with. I do think that putting pea shingle in the duct is a bad move unless you're using the rocker pipe method.

However, if you did get vermin digging through the pea shingle, a bit of 18mm ply is not likely to stop them, so I still do not know what the regs have in mind.

Scubatt · 25 Mar 2017

Hi, what did you eventually do Mike, I have the same query!

Scubatt · 25 Mar 2017

Hi, what did you eventually do? I have a similar problem.

tomfe · 25 Mar 2017

The internet failed me, I wanted a rat on a digger.

You'll be fine with some ply, the foam will keep the infill out of the ducting if it rots.

Ian H · 25 Mar 2017

I'd use Perspex.

The vermin will be able to see the gravel and won't bother trying to chew through

diynot

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Soil pipe through foundations

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