The SE suggested digging 900mm deep because the soil survey said we had clay. And we have trees.
I used the NHBC foundation depth calculator and did alot of reading around foundation digs. Overthinking it all, alot.
BC said to dig to 700mm and see what was there. Guess what? No clay (well, only a tiny patch amongst loads of gravel).
So the SE suggested a new depth of 200mm. But we are already at 700mm I said. No problem he said. Fill it back in, with crushed concrete and then Type 1 on top.
So £5K for muck away and another £7K to fill the hole we didn't need to dig. Did I mention our contingency was gone?
But we have extra secure foundations. BC happy. And we have moved on.
A photo blog seems like the simplest way to show what has happened. So here we are digging it out.
We even shovelled a bit by hand late one night.
We laid some ducts. Thanks @JSHarris for swift assistance on getting those in properly. For about 10 days we got up at 6am, worked on site for 2 hours, went to work, got home, worked on site til 11pm or later. Couldn't have MBC turn up without it being ready.
Then we put the crushed concrete and Type 1 back in the hole and compacted it to level. Just in time. MBC arrived the following morning. Its now 4th July.