Rainwater (Sewer Pipe) through wall

nowImonboards

Hi all,

I'm replacing a flagstone patio with a concrete slab on a 3 year old build. When I removed the flagstones and the top layer of coarse sand underneath I found that the rainwater pipe is coming through the wall from the neighbour's house. The pipe seems very close to the surface and I was worried that the weight of the new patio slab would risk damage to the pipe. I asked around 5 different people and and was basically laughed at by most for worrying about it. I'm due to pour the slab in 2 days and have just come across this document:

Technical Guidance Document H - Drainage and Waste Water Disposal

There is a section which states:

1.7.1.2 A drain may run through a wall or foundation. If it is necessary to build the pipe into the wall or foundation either -
(a) an opening should be formed to give at least 50 mm clearance all round the pipe and the opening masked with rigid sheet material to prevent the ingress of fill or vermin. The void should also be filled with a compressible sealant to prevent ingress of gas, or

(b) a length of pipe (as short as possible) should be built in with its joints as close as possible to the wall faces (within at most 150 mm) and connected on each side to rocker pipes with a length of at most 600 mm and flexible joints (see Diagram 12)

In my case there is a gap in the block work but it doesn't look to be 50mm above. It is filled with loose chippings which I don't think counts as compressible sealant or rigid sheet material.

In addition, the nearest joint is just over 1m away from the wall and there is no rocker section.

Is it risky to pour a slab on top of this considering (1) the shallow depth of the pipe and (2) the lack of adherance to the guidelines (a) or (b) above? The base around the pipe has not been filled with 150mm of compacted hardcore so it isn't lose as in above pic.

The above document is stated as a Technical Guidance document. Does that mean it is more of a recommendation than a regulation?

If I go back to the developer now after 3 years I may be just adding him to the list of people who laughed me out of it for bringing it up.

10-10-20

It's rainwater runoff and not grey/sewer water, right?

Blast a bit of expanding foam into the hole in the wall along with 804 afterwards (to make it impenetrable to vermin). Then compact the 804 well either side of the pipe and throw on some sand, but leave the 804 just high of the pipe on either side (but well compacted). Then reuse the flags from the old patio as caps over the PVC and pour away. Issue mitigated to a relatively good extent.

Complete DIY approach, but you did ask some randomers on the internet. 😜 👍️

nowImonboards

Thanks 10-10-20.

Absolutely understood. Looking for input from impartial randomers :) Thanks very much!

It's rainwater but from gutters shared across 4 houses. When I pour the slab it will be impenetrable to vermin so that isn't much of a worry. The 804 is compacted with a small wacker on the side the pic was taken from above. However, I won't be able to get the 804 high of the pipe or it will reduce the coverage of the slab (at the point near the wall at least). I am nervous about letting the wacker near the pipe due to how shallow it is. I also won't be able to cap it with flags due to same reason. It will be pretty much in contact with the concrete at this depth. The best I could do is put a thin layer of sand over it an maybe some spare foam from a roll I have. There is no way to lower it due to falls.

If that document is a regulation I'll call the developer and see if he is willing to do anything about it.
If it is just a recommendation then I'll have to do what I can with whatever DIY approach I can at this point.

10-10-20

If that document is a regulation I'll call the developer and see if he is willing to do anything about it.

I can guess. He'll offer to do his best impression of Nero and fiddle from a distance.

I think I'd just skip that step unless you have bigger issues with the drainage or can check the extent of the issue elsewhere.

nowImonboards

If it is a regulation then I would expect he would have to do something about it.

It it is not then I wouldn't even consider calling him.

Two days to go and today will be a wash out by the time I get out of work. I'll be working in the pours of rain with 2 hours of daylight left. All additional input welcome before then 🙏

nowImonboards

The introduction states:

"This document has been published by the Minister for Housing, Planning, Community and Local Government under article 7 of the Building Regulations 1997. It provides guidance in relation to Part H of the Second Schedule to the Regulations. The document should be read in conjunction with the Building Regulations 1997 to 2010, and other documents published under these Regulations. In general, Building Regulations apply to the construction of new buildings…"

The way this reads to me, it kind of contradicts itself. Is it part of the regulation or simply guidance for ideal best practices? Does anyone know whether failure to follow the instructions from section 1.7.1.2 from my initial post is something that could/should be enforced?

I wish I had found this document much earlier….