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vik2001

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if i build over a private drain with a extension in the back running 10m in length. is this ok? i will have a rodding access at the back of the garden.
in the extension will be new connection for bathroom/kitchen. the groundwork builder doing it will design it, but it hasnt been designed by a architect or anything. so can this cause me issues when selling?
 
You can build over a drain that only serves your property, but you still have to comply with building regulations so foundations will need to be 150mm below invert level and the drainage runs must be able to be rodded, so you cant have any bends or junctions under the extension

the groundwork builder can design it but the building inspector will want to see it

It wont cause issues when selling because you will have a building regs cert for the extension
 
so your saying the sewer drain is straight onto the rodding access at back of garden, which is how it will be. But it will connections bending off into other rooms for the bathroom and kitchen, is this ok?

the other issue is the drainage runs further as its coming from the garage room, so in total its 16m to the manhole at front of house, including extension. is this to long? im worried if it ever gets blocked because the run is to long, the rodding access may not be able to clear it compared to being a shorter run?
 
vik2001 said:
so your saying the sewer drain is straight onto the rodding access at back of garden, which is how it will be. But it will connections bending off into other rooms for the bathroom and kitchen, is this ok?

the other issue is the drainage runs further as its coming from the garage room, so in total its 16m to the manhole at front of house, including extension. is this to long? im worried if it ever gets blocked because the run is to long, the rodding access may not be able to clear it compared to being a shorter run?
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16m is fine.
 
When you say the foundations have to be 150mm lower than the invert level, I don't think this is the case for me. The builder who i sacked now has made the foundation sit higher than the invert level what can I do to overcome this?
 
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noseall said:
He means the foundation bottom needs to be lower than the drain invert etc. The top of the concrete can go as high as needs be.
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So your not talking about the the top part of the foundation where the dpc level is, your talking about the bottom of the foundation at the Base, say if it was 1 metre down... that has to be lower than the invert level

So to clarify the top of the foundation level (where the bricks would be laid) has to be below the invert level of the drain?
 
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vik2001 said:
So your not talking about the the top part of the foundation where the dpc level is, your talking about the bottom of the foundation at the Base, say if it was 1 metre down... that has to be lower than the invert level

So to clarify the top of the foundation level (where the bricks would be laid) has to be below the invert level of the drain?
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the underside of the trench has to be 150mm lower than the invert level of the drain run

the reason is because weight bearing on the bottom of the trench from the structure above wont put any pressure on the drainage pipework

private drainage is usually less than a metre down on a flat site, so may not have any impact, but public drains that run across people gardens could be 3 metres down, so building over or near those has a serious impact on foundation costs
 
vik2001 said:
im worried if it ever gets blocked because the run is to long, the rodding access may not be able to clear it compared to being a shorter run?
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these days drains are cleared with jets not rods so its less of a problem, in fact building control are a bit more relaxed about drainage generally because of that
 
Ok well the bottom of the trench is probably not done yet for the drainage. I have the foundations laid only yet around the side of extension
 
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It does not need to be the whole trench lower the invert, but just the portion either side that is within influencing distance - say 500mm or so, or just the one trench that crosses the pipe if its relatively short
 
So as this is private sewer to back of my house and I don't need a build over agreement, do I need to inform thames water of how the new layout is of the drainage, provide anyone with a drawing etc?
 
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