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Piled Foundations without digging out ground


Ivan_England

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Hi I am building a house 1 metre from my neighbours (on both sides) and the SE is worried about the retaining wall holding up the house next to my house. They have proposed raising the foundation level so as not to have to dig next to the retaining wall which could potentially be dangerous. The issue with this is I would have to go back to planning to ask to change the heights, which I doubt they will say yes to due to the fact that it matches next door. Anyone know of a foundation where I wouldn't have to excavate? Or any suggestions like cheap retaining walls i could on my side of the property?

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RJS76A_000 - Proposed street scene and elevations.pdf

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Doubt that is structural given the state of it - you’ll still need a party wall agreement due to distance to the neighbours so why not do it properly and talk to them first and see what is acceptable ..? 
 

Depending on ground conditions you could probably excavate that existing wall and pour a shuttered concrete retaining wall in less than a week. 
 

How close does your foundation wall need to be to that brickwork..??

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Hi Peter,

 

Yes I have spoken to them and they are lovely. I have submitted a party wall agreement to them this weekend, and waiting to see what they say, but can't imagine it being a problem. 

 

Ok, so you think we could just take it out and replace it with a deeper stronger wall. Is a shuttered concrete wall expensive? 

 

The foundations people want us to build the piling platform right up to the wall. The actually foundations will be 1 metre from the wall. 

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I do not think that the garden wall is a structural retaining wall.  It looks to be 100mm thick with 215mm piers.

 

Your engineer will need to consider temporary as well as permanent support to the neighbouring structures.  That basement will be a bit of a challenge!

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4 minutes ago, Randomiser said:

How significant would the increase in height be, half a metre?  Why not have an informal chat with planning and see if that would be a big issue, they may accept it given the reason.

Yes the SE wants to raise it 0.6m Ok i will check. Thanks. 

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13 minutes ago, Mr Punter said:

I do not think that the garden wall is a structural retaining wall.  It looks to be 100mm thick with 215mm piers.

 

Your engineer will need to consider temporary as well as permanent support to the neighbouring structures.  That basement will be a bit of a challenge!

Well they have proposed to have the foundations piled and then built at a higher level as not to affect the wall/other foundations. I just thought planning would not allow this so was looking for other options. It's all expensive yes. 

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If the only reason to go piled is because of the wall next door I would have thought a new retaining wall with traditional foundations would be much cheaper than piling.  Are there other reasons for piling such as ground conditions?

 

If the piles will be driven only a metre from that wall is that not a risk as well due to vibration?

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The plans that @Ivan_England posted show a full basement in the proposed new house.  The footprint is close to both the neighbour and the donor house so the excavation will need support.  This could be done with driven sheet piles, trench plates, secant piles, king piles etc but will be very difficult and expensive.  While the basement retaining walls are built they will need a bit of working room around.

 

I would not consider building a basement in that location.

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17 minutes ago, Randomiser said:

If the only reason to go piled is because of the wall next door I would have thought a new retaining wall with traditional foundations would be much cheaper than piling.  Are there other reasons for piling such as ground conditions?

 

If the piles will be driven only a metre from that wall is that not a risk as well due to vibration?

Hi,

 

It has a willow tree 4 metres from it, and used to have (ten years ago) trees all the way along the plot. The pilling company don't believe the vibration would be an issue, it has been discussed and a site visit done. I didn't want to pile, but once the SE has recommended it it's hard to get out of. I will look at your suggestion though thank you. 

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8 minutes ago, Mr Punter said:

The plans that @Ivan_England posted show a full basement in the proposed new house.  The footprint is close to both the neighbour and the donor house so the excavation will need support.  This could be done with driven sheet piles, trench plates, secant piles, king piles etc but will be very difficult and expensive.  While the basement retaining walls are built they will need a bit of working room around.

 

I would not consider building a basement in that location.

It's not a basement it's simply building on the ground there. Here is a photo (taken in summer) of the back of that plot showing the height. :)

Back of house.jpg

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19 minutes ago, Ivan_England said:

Hi,

 

It has a willow tree 4 metres from it, and used to have (ten years ago) trees all the way along the plot. The pilling company don't believe the vibration would be an issue, it has been discussed and a site visit done. I didn't want to pile, but once the SE has recommended it it's hard to get out of. I will look at your suggestion though thank you. 

OK, with a willow that close even in the best of conditions you will need some pretty deep foundations I suspect.  You could use the calculator link to here with your specific information to give you an idea.

https://www.labc.co.uk/news/trees-and-foundations-foundation-depth-calculator

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18 minutes ago, Temp said:

Who owns that wall? If it's yours I'd be tempted to rebuild it now rather than wait for it to fall down in a few years?

 

 

It's a party wall so jointly owned, yes a few people have said it might be worth replacing. 

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