Manhole turned up in Foundations - see pics.

[lj329]

Hi All

Started digging out the foundations for a single rear extension of my house. The ground is a bit tough but was going ok until we hit an unused manhole - see pics.

There wasn't any metal cover on the hole, it was full of earth. I dug away through this and hit a thin cement plug about 40 cm in. Underneath I exposed the first of the metal rung steps before falling into a fit of depression.

I will get LABC out next week but was wondering what experience anyone else might have had with similar problems.

Thanks for any info!

Lee

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• lj329
• 30 May 2010
• 1

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• lj329
• 30 May 2010
• 1

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• lj329
• 30 May 2010
• 1

 

[ajrobb]

Curious! I wonder if it's an old shared sewer. Where I grew up we had a shared private sewer that served the back of several houses before connecting to the public sewer. Maybe it collapsed and the houses now connect directly to the public sewer.

As long as you know where your drains go now, I wouldn't get depressed at this stage. It sounds like the old infill has had years to settle to provide a firm footing.

 

[noseall]

If it is redundant then dig it out, i.e. break it up and remove any masonry that interferes with the trench.

What is all the white stuff, looks like a dusting of snow?

 

[ColJack]

could be a fallout shelter

or a private water pit..
my nan's old house had a pit under the kitchen floor for collecting rainwater for washing etc....

 

[noseall]

my nan's old house had a pit under the kitchen floor for collecting rainwater for washing etc....

...mine too!

 

[lj329]

thanks,

the site previously had several old farm buildings on it before my house was built in 1975.

It looks like there was an old road that ran through my back garden hence the hard dig. The old sewerage system probably followed the road.

All our drainage now goes out the front of the house so shouldn't be affected.

I am hoping that the BCO will have his happy head on and not demand to see the bottom of the damn thing. I will try and get them out tomorrow and see what the verdict is.

Not sure what the "snow" is - I think I must have set the camera on some fancy setting.

 

[Nige F]

thanks,

the site previously had several old farm buildings on it
I am hoping that the BCO will have his happy head on and not demand to see the bottom of the damn thing. I will try and get them out tomorrow and see what the verdict is.

.

Slurry pit from a dairy

 

[lj329]

I am hoping that the BCO will have his happy head on and not demand to see the bottom of the damn thing. .

Hey guess what - The BCO wants to see the bottom of the damn thing. He would not be happy with the footings on disturbed ground.

Well the brickie was fairly disturbed when I told him

He has dug one side out and it goes about 7ft down. BCO needs to come again tomorrow to have another look and hopefully give me a resolution.

I will remember to take my camera and post some pics.

 

[noseall]

[Well the brickie was fairly disturbed when I told him

EXTRAS EXTRAS read all about it!

 

[lj329]

Ok, the resolution is that we have to dig a meter wide pad on both sides of the manhole, to the bottom of the structure on both sides. Then concrete and lintel so "no load should be placed" on the manhole.

This seems like overkill to me but I am fairly stuffed

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• lj329
• 2 Jun 2010
• 1

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• lj329
• 2 Jun 2010
• 1

I either pay the brickie, or employ a structural engineer to come up with another method, either way the cheque book is getting hammered!

 

[ColJack]

my nan's old house had a pit under the kitchen floor for collecting rainwater for washing etc....

...mine too!

Adrian? is that you?

 

[ColJack]

dig it out inside.. see what's down there.. if it's dry or not..

then either knock it down or fill the bloody thing with concrete ( hey look, a pillar )

 

[Static]

As stated above filling the thing with concrete is always an option.. either that or break it down below the footing level and put a capping slab over it..

 

[JohnD]

have you found out yet what's at the bottom of it?

were there any steel rods in the brickwork?

 

[lj329]

We found it was part of the old sewerage system for the old street of houses that used to be on the site. There doesn't seem to be any rods in the brickwork - there are steel steps on the inside, but nothing much else.

Digging down inside it would be painstaking as it has been backfilled, and is about 8ft deep. I 've gone down about 2ft inside and even at that depth I was using a trowel to try and scoop earth out.

I tried suggesting lots of alternatives to the BCO, including knocking it flat to the footings but he is adamant the base of the concrete must touch undisturbed soil. So even if we did knock it out we would still have to dig down either side to the bottom of it.

I wouldn't mind but this will only be a single storey extension, and this part is right under where the french windows will go, not a block of flats!