Drain Embedded In Oversite Slab
Posted 28 April 2013 - 12:51 PM
Hope someone can help here, please....
I'm building a small single storey extension which includes a bathroom and separate toilet. Because of site restrictions, I need to join the new foul wastes to the existing drain. This is physically quite straightforward, there's a convenient rodding eye to join to, but I don't have enough height to keep the new drains below the oversite slab. I therefore want to encase the drain pipe partially in ths slab. Local BC manager says it's OK if I submit a suitable design signed off by a structural engineer. Two builders have said they've seen it done, not ideal, but possible by stregthening the slab (presumably with extra thickness and rebar). My current engineer won't quote.
I can't believe this is such a big problem - does anyone have any suggestions?
Thanks in hope,
Posted 28 April 2013 - 02:53 PM
That's what mine does at the moment, as a consequence of the bathroom being extended. Only downside is the need to box in the soil pipe, but in my case I managed to run it behind built-in bathroom cabinets (with some surgery to the back of them!).
Posted 11 May 2013 - 01:40 PM
I think he is being unnecessarily cautious, what do you guys think? I've had suggestions including supporting the slab on a sleeper wall each side of the drain run, and putting a thin (I assume they mean steel or timber) cover over the pipe; the insulation and floor screed would then be laid over all. Another suggestion was to make the floor in the bathroom & toilet a suspended timber floor, thus gaining the thickness of the absent slab as usable clearance. Has anyone come accross this before?
Edited by beejay, 11 May 2013 - 01:41 PM.
Posted 11 May 2013 - 01:54 PM
Posted 11 May 2013 - 04:39 PM
Posted 11 May 2013 - 05:34 PM
That's the best news I've had all day. Brilliant!
Posted 11 May 2013 - 08:11 PM
Posted 11 May 2013 - 08:43 PM
Temp is right, beam & block may offer a solution if the engineer can specify it thin enough, with insulation and screed on top.
This is a steep learning curve, and I thought that sub-ground level was the easy bit! Wish me luck with the engineers next week!
Posted 11 May 2013 - 08:51 PM
Also, if I was to build like that, the drain would be embedded in the eps. Any thoughts?
Posted 12 May 2013 - 07:37 AM
There's no problem with embedding ABS soil pipes in EPS, but there is with some types of PVC pipe. AFAIK, most underground soil pipe is OK in EPS.
Edited by jsharris, 12 May 2013 - 07:39 AM.
Posted 12 May 2013 - 08:09 AM
Or would that not happen in practice?
Posted 12 May 2013 - 08:47 AM
Or would that not happen in practice?
It depends very much on the ground conditions and the degree of heat transfer. Soil can be very thermally conductive, especially when damp. GSHPs rely on this to suck heat from a wide area of ground via some fairly narrow pipes. All the evidence from measurements of under slab soil temperature suggests that there is only a small increase in temperature from heat lost from the house through the heating season, perhaps 1 deg C at most. To all intents and purposes the ground is always significantly more thermally conductive than the under slab insulation, so will conduct heat away faster than it is conducted through the slab.
As this is an interesting point, I've started another thread to avoid disrupting this one.
Edited by jsharris, 12 May 2013 - 08:47 AM.
Posted 12 May 2013 - 09:14 AM
Posted 28 July 2015 - 02:55 PM
On the off-chance that you're still around, I'm in pretty much this exact situation - how did it turn out in the end? Do you have any useful info or photos you'd be happy to share?
I'm an innocent punter embarking on my first extension project... Thanks and fingers crossed!
Posted 28 July 2015 - 09:11 PM
I'm not sure how much i can help you. As I suspected, and mentioned in my first post, there never was a problem. What we had was an architect trying to justify his enormous fee. In the end the drain was buried in the oversite with some mesh to strengthen it, and the rodding eye came out through the external wall, disguised by careful planting. Structural engineer and BC manager signed off ok, everyone happy. The attached photo shows thew basics. Let me know if you need more.
Posted 29 July 2015 - 08:05 AM
How far below floor level was the highest drainage pipe in the end? Is that roughly floor level I can see around the outside?
I have a slight variation of the problem in that the existing drain we'll be connecting to is only about 300mm below the floor, and we need to drop to that AND replace an inspection cover that's currently raised to approx 150mm over the intended floor level. Fun and games.
Posted 29 July 2015 - 08:11 AM