How deep do foundations need to be?

[Joeylegend]

How deep do foundations need to be?

I am about to start digging my own foundations (to save money) For a single storey one roomed extension from the dining room at the back of my house, out.
I am going to lay out the area , but how far down do you need to dig?

I will hire a mini digger?

 

[stuart45]

The depth can vary greatly depending on the type of ground eg rock,clay, silt. Also trees close by.

 

[Joeylegend]

There are some small fir trees, nothing to worry about, and the ground is clay

 

[noseall]

Typical minimum depth is 1m below ground level.

Building control may accept less if they are familiar with ground conditions and if there is no point in going deeper, i.e. if at 700mm deep for example, the ground is clearly non fertile, virgin earth and is not likely to be any more adequate/different lower down.

Localised drains and other services can affect depth too. As can changes in gradient.

No matter what, you will need to be digging out non-disturbed/virgin earth. If it is not, i.e. made-up ground, then you have no choice but to keep digging.

 

[^woody^]

Wont these become big fir trees one day?

You are looking at at least 1m, and then see what the BCO says

 

[Joeylegend]

the fir trees may just be taken away,

Did realise it would be as much as 1m, whats that in feet?

 

[^woody^]

I don't know about feet, but its up to your belly button or just a bit deeper than a normal shovel

 

[swidders]

the fir trees may just be taken away,

Did realise it would be as much as 1m, whats that in feet?

about 3 foot

 

[Shytalkz]

I don't know about feet, but its up to your belly button or just a bit deeper than a normal shovel