Build over agreement (Class 1)

[John Williamson]

I have a 100mm drain pipe which will go through my foundations at a depth of 1m.

The manhole is outside the footings of the extension so it only the protection of this clay drain I need to be concerned about.

The foundations are very deep, up to 2.4 meters.

I am thinking of something like this. Would this work?

 

[^woody^]

No. You'll get uneven foundation settlement

 

[John Williamson]

No. You'll get uneven foundation settlement

Thank you woody. I have searched and searched and found no examples of what is required. Any clues?

 

[^woody^]

A continuous foundation with a hole in it for the pipe. Or flexible connections on a built-in pipe.

 

[John Williamson]

A continuous foundation with a hole in it for the pipe. Or flexible connections on a built-in pipe.

Thanks woody. The pipe is existing so they can just pour the foundations around it? No lintel support required?

 

[^woody^]

Yes the foundation can go around a pipe, but allowance for movement had to be made, so they need to devise a method of keeping the concrete off the pipe.

 

[John Williamson]

Yes the foundation can go around a pipe, but allowance for movement had to be made, so they need to devise a method of keeping the concrete off the pipe.

I've heard of people wrapping in bubble wrap. Sound acceptable or something more substantial?

 

[chappers]

No. You'll get uneven foundation settlement

Why do you say that. essentially that's what we always do with the only addition we line the sides and top of the granular backfill with celotex. If the crown of the pipe has less than 150mm backfill over it then we would sleeve the pipe and fill with foam using flexi joints either side.

 

[^woody^]

No. You'll get uneven foundation settlement

Why do you say that. essentially that's what we always do with the only addition we line the sides and top of the granular backfill with celotex. If the crown of the pipe has less than 150mm backfill over it then we would sleeve the pipe and fill with foam using flexi joints either side.

Because that what will happen with two unconnected foundations.

Going by the OP drawing, 2/3 of the foundation depth are separate. One half will move and crack that 1/3 section above the pipe

 

[John Williamson]

No. You'll get uneven foundation settlement

Why do you say that. essentially that's what we always do with the only addition we line the sides and top of the granular backfill with celotex. If the crown of the pipe has less than 150mm backfill over it then we would sleeve the pipe and fill with foam using flexi joints either side.

Because that what will happen with two unconnected foundations.

Going by the OP drawing, 2/3 of the foundation depth are separate. One half will move and crack that 1/3 section above the pipe

I understand, so something more like this? And would gravel give the appropriate movement?

 

[theprinceofdarkness]

I would not put gravel between the foundations and the pipe. Use foam or clay ("pugging").
Frank