Foundation depth for single storey side extension

[Skvenu]

I need to extend on the side to close the ally way and use it as a utility.My structural engineer specified a depth of 1.2 mtr for strip foundation.
The extension will be a flat roof of size 4.5 mtr wide and 1.2 mtr projection with standard height of 2.4 mtrs.

My neighbour is using the party wall act to get a surveyor but it is not worth going down that route due to the size of extension.

Is there any other way around this to not dig more than 300mm (to avoid the party wall act)

Any help appreciated.

Thanks in advance!!!!!!!!!

 

[tony1851]

Why not put your foundation at the same depth as the existing house foundation - presumably your neighbour's foundation will be at the same depth?

 

[jeds]

Foundation depth really has little to do with the size of the building. It's to do with preventing the building from moving about and cracking. What are your ground conditions? On clay a minimum of 900mm is normal because clay can change volume dramatically due to drying, wetting and freezing. If you have hard rocky conditions you could get away with a lot less. Alternatively pull the foundation when she's away. Get it poured before she gets back and there's nowt she can do.

 

[tony1851]

@OP;

Do you actually know the depth of your neighbour's foundation?
Does your neighbour? Has he or she actually seen it? Has anyone seen it?

The PWA only applies if (among other things) your excavation goes below the level of the neighbour's foundation. So how can you apply the Act if you don't know one way or the other? You can't be expected to just assume the depth. As jeds, just do it and be done; could it be done over a Friday and weekend?