foundation

[Mikest]

Hi everyone, can any one tell me if 10cm difference at the trench bottom is something to worry about. I have a meter deep 600 wide foundation, but in some places is 87cm deep. should i be worried about this and call the digger back?

i going to build 2storey on this so i need them to be adeqaute, he dug around 60cm in to the chalk if that helps.

 

[RedHerring2]

The BCO will pass it or he/she won't. Go from there.

 

[Mikest]

He has passed it, i rang to ask him a few days later if that foundation depth would be o.k for future 2 storey and said yes it would be. But again i dont/wont have this in writing so want to be sure.
last thing i want is to be told on second storey stage that foundations are not adequate.

From your experiance would i be ok? All the foundation is minimum 90cm below external ground level. 40-50cm of this is chalk.

 

[jeds]

Depth of foundation isn't a load bearing issue. It is a question of frost protection and saturation. On clay 900mm is the absolute minimum because clay is shrinkable so you must avoid any possibility of freezing at the base of your concrete and you don't want it drying out. On chalk none of this applies. 600mm is adequate on most chalk sites.

 

[Mikest]

thankyou, last question. How soon can you start building the extension after the concrete pour. I was thinking of setting out firsts courses the same day. Would this be ok?

 

[freddiemercurystwin]

Take plenty of photos before and after the pour to prove depths if you need to prove their depth/suitability for an additional storey later on. Or get it in writing.

 

[r896neo]

you can build on it the next day. It'll be too soft to repeatedly trudge about on it on the same day