Bath waste pipe in old cavity wall

[cdh]

Does anyone know if it's OK to run the waste pipe through a cavity wall to the soil stack?

I've built an extension at the side of the house and therefore the cavity wall is no longer an outside wall and rather than boxing out the pipe in the bathroom I wanted to run it along the cavity wall.

It will be a length of about 2m and I was planning on putting some form of access half way, just in case of any future problems.

 

[Richard C]

Not exactly sure what you mean; do you intend running the waste through the wall at 90 degrees or along inside the cavity? Is the soil stack on an outside wall? What size is the waste?

A sketch always helps with this sort of thing.

 

[cdh]

The pipe will run inside the cavity for about 2m and will be either 40mm or 50mm.
The soil stack is on an inside wall.

 

[kirkgas]

first thought would be never to run a pipe inside a cavity, as it could get damaged, and cant be properly supported (unless major work was done to open up wall), it shouldnt freeze if graded properly as it should always empty, but it just doesnt seem right as it will never be inspected,

 

[Richard C]

Running pipes or cables inside a cavity is not normally permissible; you say the cavity is now on an inside wall, is this over the full height of the cavity or is it just ground floor? If there is cavity insulation, you will never find a way through & depending on the cavity width & position of wall ties, you still may not find a way through. Problem is the cavity remains open throughout the property &, TBH, I don’t know how LABC would view this one; a phone call may well sort it out & I would be interested to hear what they say.

Still finding it difficult to envisage but if the stack is inside, how do you propose to get a length of waste pipe into the cavity & back out again to connect it up &, as stated, how would you support it mid span?

 

[tryitandsee]

To give all the wrong advice, if it were me, as long as the waste pipe was inserted all the way in the cavity in one length of pipe, no joins, with access tees each end, so that I could rod it successfully without hassel, I would go for it.

 

[Richard C]

To give all the wrong advice, if it were me, as long as the waste pipe was inserted all the way in the cavity in one length of pipe, no joins, with access tees each end, so that I could rod it successfully without hassel, I would go for it.

Yea maybe; but I suspect that has a lot to do with your username

As all things in life, balance is important but it's a real PITA when you start getting asked awkward questions about BR compliance & paperwork for your extension when you come to sell up. Make that phone call to get right, it costs nothing; but tell lies on your future vendors questionaire form at your peril, it could cost you a fortune, or at least the positive equity you thought you had!

 

[tryitandsee]

R C is totally right, but I can't help but think it would be much the same as running pipework under chipboard and plaster board first floor construction, ie the hassle of getting to it for repair!

 

[Richard C]

R C is totally right, but I can't help but think it would be much the same as running pipework under chipboard and plaster board first floor construction, ie the hassle of getting to it for repair!

Fair comment &, TBH, I’m not sure about how LABC would view this one

But given my previous comments about the stack location, what’s potentially in the cavity & the size of the holes you will need to be to get a 40/50mm waste pipe in there & back out again anyway I have doubts about the feasibility of it anyway.