Unknown foundation depth and a different building length

[oldkettle]

Hi, 

 

Attached pictures show our existing wall and the neighbours' garage about 1.8m away. I am trying to understand a few things. 

1. If the Council Building Control won't find any documents showing foundation depth, is excavation my only option to establish this? And based on the slope does it mean I may have to dig in multiple places as it can be stepped? Am I allowed to start digging without serving any notice as long as I don't go below the bottom of their foundation? 

 

2. We want to extend at the back well beyond the length of their garage. How does 3m rule work when there is nothing on their side when we draw a line perpendicular to the border? Or is it 3m regardless of an angle? 

 

3. For those who had a basement and was affected by the Party Wall Act : how expensive were the extra steps, technical and legal? 

 

Thanks in advance. 

 

[Declan52]

Just lift some of the paving bricks and a slab and dig down. A post hole digger will get you over 1.2m deep in a hole not much wider than 600mm square. This will give you the depth of the top of the concrete. If you need to find the depth of concrete you can use a spade to scrape down the concrete and the post hole digger to remove the spoil.

https://www.screwfix.com/p/roughneck-fibreglass-post-hole-digger/35835

 

 

 

[oldkettle]

3 minutes ago, Declan52 said:

Just lift some of the paving bricks and a slab and dig down. A post hole digger will get you over 1.2m deep in a hole not much wider than 600mm square. This will give you the depth of the top of the concrete. If you need to find the depth of concrete you can use a spade to scrape down the concrete and the post hole digger to remove the spoil.

https://www.screwfix.com/p/roughneck-fibreglass-post-hole-digger/35835

 

So no need to ask them first? I would of course let them know as we have good relationships. 

 

What about the stepped issue? What if the hole at the lowest point goes below the foundation 3 meters up? 

[Declan52]

Don't need to say to them if you don't want to. Your opening a small hole on your property.

Good chance it will be stepped so might need a hole at each end and one in the middle.

[oldkettle]

4 minutes ago, Declan52 said:

Don't need to say to them if you don't want to. Your opening a small hole on your property.

Good chance it will be stepped so might need a hole at each end and one in the middle.

Yep, I understand I will need multiple holes. But it is likely that the one at the lowest corner will end up being below their foundation in the middle, so I wonder whether this is a problem. 

[Declan52]

But your only opening a small hole so won't cause any damage to theirs.