Digging alongside neighbour's foundation

[paulweller84]

Hi,

I'm currently planning a single storey extension on my house and it is my intention to build right to the boundary. On one side this will mean digging footings along the property boundary - right alongside my neighbour's existing extension. I have dug a small hole to check their foundation and it goes down approx 1m, which is what mine will be. My question is, is it safe to excavate directly alongside the existing footing?

I have attached a diagram. The neighbour's extension foundation (green) will sit directly next to the proposed foundation for my new extension (red). I will have to dig down where the dotted yellow line is, and it is this that concerns me. I will be removing the earth along the side of the foundation. If this method is not safe, what other alternative is there? We don't have enough width in the garden to build away from the boundary and leave a gap.

 

[SFK]

Wrong page.
Deleted

 

[mikeey84]

As I understand it, but I'm no expert...

Yes it is safe, as long as you don't go lower than their foundations (I think you can, but have to be very careful and dig/fill in a different way)

I understand you will probably need a party wall notice if you are that close.

Additionally, you say your foundations will be 1m deep. Unless you have had a test out inspected by building control, my understanding is that it's they who decide how deep your foundations go. (Given your neighbors go 1m deep, the chances are you will be fine with that, but it's very dependent on what the soil conditions are)

 

[paulweller84]

As I understand it, but I'm no expert...

Yes it is safe, as long as you don't go lower than their foundations (I think you can, but have to be very careful and dig/fill in a different way)

I understand you will probably need a party wall notice if you are that close.

Additionally, you say your foundations will be 1m deep. Unless you have had a test out inspected by building control, my understanding is that it's they who decide how deep your foundations go. (Given your neighbors go 1m deep, the chances are you will be fine with that, but it's very dependent on what the soil conditions are)

Thanks for your reply. I'll be running this by the building control guy.

 

[^woody^]

No its not safe. Foundations can move sideways no problem if exposed.

You need to assess it and work hout how quick you can fill the trench and if the foundation will be stable for that time exposed, or if you need to work in bays, or use another method.

How you do it is not a building control concern and they should be telling you as they are not experts in this, and you can't rely on what they say in any case, it's all down to you to sort it out or employ professional advisors

 

[Leofric]

My question is, is it safe to excavate directly alongside the existing footing?

I bloody hope so because that is what my neighbour did when they built their extension at the side of my house ,and they said building control had seen it and were happy with it

 

[mikeey84]

I suppose it depends on how much of your neighbors foundations you are exposing....

 

[mattylad]

Can sections be exposed and filled, then other sections opened ad filled once the first have dried to prevent lateral movement?

 

[John D v2.0]

Our builders just went for the dig it on Thursday and fill it in Friday method, not sure if that's recommended but the original footing remained floating where it was supposed to be.

 

[Leofric]

not sure if that's recommended but the original footing remained floating where it was supposed to be.

Hope it wasn't literally floating

 

[^woody^]

that is what my neighbour did

So it seems.

 

[Leofric]

So it seems.

don't understand your reply , a bit odd even for you

 

[Notch7]

Can sections be exposed and filled, then other sections opened ad filled once the first have dried to prevent lateral movement?

Well yes, but then you have day joints -which can be overcome with rebar

More importantly no buikder will want to dig out like that - diggers dig up nice long straight trenches, much quicker than separate holes.

The buikders solution is fill it in quick, hope it diosnt rain.

 

[^woody^]

don't understand your reply

Give it time.

 

[Leofric]

Give it time.

Perhaps one of your spokespeople could explain it.