Help With Foundations Please

[stinkdog]

Hello

I am looking at the possibility of a single storey side extension. My problem is, where the sidewall of the extension would need to be, are foundations for a retaining wall which is between me and my neighbour (my neighbour is 1.2m higher then me). I need to build this sidewall (which will form a garage) parallel to the retaining wall leaving a gap of approx 4"/100mm)

Does anyone have any idea's here, can I modify the foundations of the retaining wall and replace with a trench fill foundation to the same level to enable me to build along this line. I know the retaining wall founds are not good enough for me to build on.

I know this is probably not an unusual situation, just I have never come across it before.

Any help will be gratefully received......many thanks for reading!!

 

[noseall]

This is definitely a job for a structural engineer to look at. One particular aging fellow on the forum may be able to help. Offer him a Werthers original and he may advise.

His name is Shytalkz.

By the sounds of it, you are going to lose the retaining wall. This may need re-building or indeed use the extension wall as a retainer, due to the fact there will only be 100mm remaining betwixt extension wall and retaining wall.

As next doors' ground is four feet higher it may mean a lot of earth moving too. How close is next doors structure to the boundary wall?

 

[alittlerespect]

If you want to remove the retaining wall you may be in for a bit of a rough ride with your neighbour and you will need to enter into 'party wall' agreement with your neighbour, however, if the retaining wall is his property then you cannot carry out any activities on it unless you have the neighbours approval, which I suspect would be a howling 'no way over my dead body'!

Therefore, you will definitely need the services of a party wall surveyor to advise and negotiate on your behalf with your neighbour, once you know your position with the neighbour and assuming that all ends well then you can proceed to the services of the structural surveyor, as recommended by noseall.

 

[stinkdog]

Hi

Thanks for the replies. I have already established that the cost involved to remove and rebuild the retaining wall would be too great to even contemplate.

The extension is to be a single skin attached garage (but more like a store as it will be too small to get a car in) and at just a smidge over 2m width I don't really have any room to make it any less wide.

Your responses are in line with others I have received from various parties, but if I look in the streets around my house there are atleast a dozen houses with similar extensions, some double storey, all with the retaining wall still in place and unaffected.

I think this project may have to knocked on the head. I have tried to gain advice from all of the local structural architects and not one of them will even give me an idea as to the cost effectiveness of any foundation design, unless I hand over £1200 - that was the cheapest!!. Don't get me wrong, I want to do the job correctly and don't mind paying for that, but what I don't want to do is to pay a structural guy £1200 and then find out it's going to cost me £10k to build a reinforced foundation as this would just make the job unfeasable. I hope this makes sense.......