Step in foundations, flatness of bottom of foundation, sleeving

[Stu84]

Hi everyone. Few Foundation-related Qs. Thanks all for their help, new to this so steep learning curve! Excuse long post and numbering.

 

1) Mid-way through digging foundations for a small side extension. Wondered if OK to step the foundations like drawn in the picture attached? Alternatively would a gentle slope be OK as shown by dotted line (gut instinct says no but builders having hard time matching depth at far).

 

 

2) How level should the bottom(s) of the trench be before the pour? Is a variation/bumps of 2-3 inches acceptable, checking depth every few foot measuring relative to a datum? Or should we be more accurate across the entire length e.g. talking spirit levels laying flat along the bottom.  I guess latter would be preferred, but I’m talking real world.

 

3) Have a 110mm surface water pipe that runs perpendicular right through the two return foundation trenches (which are 600-650mm wide). Building inspector seems happy for us to wrap a bit of insulation around pipe, then sleeve with a split larger diameter pipe, with a few jubilee clips to close the split. Then support the pipe on a concrete block or two and pour right over it. It’s great that the BI is open to this but wondered what the community thought? There will be about 100mm concrete above the pipe. I could place (float) a few off-cut lengths of approx 400mm rebar into the concrete immediately above the pipe if that would help?

 

Thanks you!

[ETC]

For what it’s worth:

 

Steps are fine.

Bottom should be flat - not sloping.

I wouldn’t place concrete over the pipe - shutter either side and lintel over it.

[Stu84]

Thank you so much for your reply.  Yes we shuttered pipe in the end and will now lintel over.  Was very difficult shuttering, as all the pea gravel starts to pour out when trying to key the boards into the side.

 

We didn't step in the end.  But probably should have to save on concrete as inspector said he would have been happy.

 

Thanks again.