Drain line

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Hi all. I have a question regarding a side extention. There is currently a manhole then 3 meters down a small kitchen drain and another 2 meters down a downstairs toilet drian.

I was wondering what would be the best way in laying a concrete floor over the extention.
The floor would need around 50cm concrete to level to match the dpc level. The drians are already i presume a meter into the ground; is it a good idea to add another 50cm concrete on top?
I was thinking of having some sort of a housing for the drain line so in event of a drain collapse it could be easily accessible. Any thoughts?
 
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I think you may need to speak to building control. you'll probably have to move the entire drain run outside the proposed extension or at least reduce or remove the chambers within the building.
 
If you’re going to build over an exiting foul drain, it must be bridged where it passes through the foundations. You must also be sure it’s in good condition so I would replace it & move the run outside the building line if you can. You cant just cover manholes either as they usually mean there is a change in direction or another connection so you must maintain access for clearing blockages which LABC will be interested in as stated. Can you imagine the scenario where a few months after building your extension you have to dig the floor up again because the drain has collapsed or you cant get access to clear a blockage.
 
If you’re going to build over an exiting foul drain, it must be bridged where it passes through the foundations. You must also be sure it’s in good condition so I would replace it & move the run outside the building line if you can. You cant just cover manholes either as they usually mean there is a change in direction or another connection so you must maintain access for clearing blockages which LABC will be interested in as stated. Can you imagine the scenario where a few months after building your extension you have to dig the floor up again because the drain has collapsed or you cant get access to clear a blockage.


Richard, I'm wanting to keep the manholes exactly where they are. I was thinking of using a sealed man holehole cover. So the access for clearing drain blockages wont be a problem.
I want to lay the flooring in way way so i can get to any where in the drain line with out having to rip the floor too much in the event of a drain collapse. how could i do this?
 
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The point is to replace the drain and protect it sufficiently so that there'll be no chance of it collapsing and no need for replacement for many years. Position the manholes to suit your layout ie not under a kicthen unit. They can be under carpet or made to fit in with a tile layout for eg.
 
So are you saying its fine for to add another 0.5mtr of concrete on top of the floor? This would mean the drain would be around 1.5mtrs or more in to the ground.
 
It doesn't really matter what you put down if you've allowed for it in your new pipe run. Out of interest why not just suspended timber or concrete anyway?
 
thanks for reply freddy, i havent really thought about suspended timber flooring. What do you think, is it better to suspend timber?

I defo want to leave easy access for the whole drain run within the extention. I was thinking housing the drain pipe run with timber and concreting the rest of the floor. so say If I ever had to replace the drain pipe, i only have to take up the carpet and screw of the timber housing and and thats it. Does this sound ok?

Im looking for the most cost effective way, aswell as the least trouble some in the event of a drain problem.
 
I'm not sure of the cost difference but a suspended timber or concrete (beam & block) floor seems more logical to me, a 500mm concrete slab seems a bit excessive. You will also only have local pressure on the drain beneath the foundations which can be overcome with lintels anyway. Anyhoo, you should not need access to the drain along its length if it has been replaced only access to the junction via the manhole if ever there was a blockage. To not replace existing drainage beneath a new extension seems a bit short sighted to me. Your suggestion of having access to the whole drain run is bizarre and alien to me.
 
OK freddy thanks for reply. Im going to have to look in to it further. I know the norm is to only have manhole access, and i also understand thats its highly unlikely to have a drain collapse especially if the drainage line is newly replaced; but i just dread the thought of having to rip out the floor incase there was ever a problem. However unlikely it may be.

I'm not scared in trying something thats a little unusual as long as it doesn't have any negatives. And honestly speaking freddy i cant see any problems in keeping a housed access to the drainage. I would love to hear your pros and cons in doing it this way.
Say if a customer requested it like this, how would you tackle it.
 
As for amount of concrete fill, i will measure it when i get back, i may have over estimated a little, i think it more likely to be around 250mm/25cm. Sorry for the inaccuracy
 
My two penn'orth:
Can't you build up the access chamber to floor level and use a double seal cover?
 
My two penn'orth:
Can't you build up the access chamber to floor level and use a double seal cover?
That's exactly what were talking about. Not an access cover at ground level but at floor level.

If a customer asked me to do design this I'd persuade them otherwise, heck you can even do trenchless sewer repairs. A bit like someone asking if there was software available specifically to design brick walls, there are easier ways to go about it! :cool:
 

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