Underpinning - usual projection distance from wall?

[raine]

Can anyone tell me how far, very roughly, the concrete generally projects from the face of an underpinned wall please?

Been digging a small trial pit to expose the foundations of my neighbour's Victorian flank wall, as I need to build some new footings adjacent to this, and have exposed some concrete, six courses below ground.
It extends at least 300-400mm from the face of the wall (no spread foundation), but I don't think it's original. It looks less rough than other Victorian concrete I've seen, the top isn't level, and it doesn't quite go all the way to the end of the wall.

So, before I go digging all the way along the wall to figure out what this is, it would be good to get some advice on whether it might be underpinning.

Thanks.

 

[^woody^]

Unless it's been specified otherwise, it's vertical to the foundation being underpinned.

 

[raine]

Ah, ok, thanks Woody.

I suspect this concrete may be protecting an old drain or something. I'll dig a bit further along and see what I uncover.

 

[KenGMac]

raine, good evening.

Suggest you consider that the wall has been underpinned in a "Traditional way" meaning mass concrete fill into pre-excavated sections taken under the existing wall.

If the above were to have been undertaken then the wall below ground may? have indications of gouge damage by the work involved?

I do not know how English Building control works, is there a "Portal" where you can find out if there were any applications for such work having been undertaken on the property? I have used such "Portals" in Scotland to determine what has been applied for in a Property that I am Surveying, indeed a most helpful tool.

Just something to consider?

Ken.

 

[raine]

Great, very informative post, thanks Ken.

Good to know that it could be either flush with the wall or mass fill type with less precision.

There is no portal for building control apps in England (unless I've missed something!), but I'll ring the local Building Control Officer and ask if there is anything on record - easier first option than doing more digging!

 

[KenGMac]

raine, good evening again.

The system i referred to - Traditional Mass Concrete underpinning consists of.
A/. Excavate a trench down to and below the existing wall,
B/. Then excavate under the wall, + clean off the underside of the brick.
C/. Pour in a fairly runny mix of Concrete so the Concrete floods under the brick wall.
D/. These trenches are "Generally" no more that 1.0.m in length along the entire length of the wall, it does mean that you can excavate more than one trench and Concrete more than one trench per day.
E/. The trick is do not under any circumstances excavate two trenches near to each other.
F/. A time delay between excavating and Concreting the trenches is also a requirement meaning a day or two between each trench, so that the previous trench can "Set up" and become firm to ensure the load from the wall is fully supported.
G/. If the above has been installed, then differences in top surface level should be apparent, likewise differences in outward distance from the wall should also be noticeable?

Shire piling [ a proprietary brand] is used on existing foundations with local outcrops of Concrete.

There is another type of system that surrounds the property with a reinforced concrete beam.

i am glad that I live where I do and can interrogate the portals and get all the Information I need sitting here rather than a call to a Harassed B/C Office?

Ken