Concrete found during excavations- does it need to be removed?

[JR172]

Hi, I would appreciate some advice pls.

While digging our foundation trench for our ext our builders uncovered a concrete block coming out from under our garage walls. It's 600mm from ground level before the block starts, and there's around 30mm under the block. It's 500mm wide and 280mm deep.

Our SE has said we need to cut it away as it won't bond to the new concrete. Unfortunately our builders are refusing saying it's not safe and there isn't enough space.

I wondered whether anyone had a point of view that's different to either of the above as we are currently stuck in the middle. Pics should be attached

 

[^woody^]

Underpin it

 

[stevie888]

Your SE is an idiot: it doesn't need to bond

 

[Ivor Windybottom]

I can't understand what we're meant to be looking at and how it relates to what you're building.

If it would be within your new concrete then it would weaken it. It needs to all be one contiguous pour, and not have a detached muddy lump in the middle of it.

It sounds like your builder's making excuses. Smash it out. Chances are it's just leftover mortar from when the house has built, so it would break out easily and its weakness is another very good reason to remove it.