Block and beam foundation

[Hobo84]

Hello,

I'm currently digging my trenches for an extension. The only sections that are left to dig are for 2 internal foundations which will support the weight for a block and beam floor. These are quite awkward to dig long the side of my existing house.

My query is how deep would they need to be? The trenches I've dug so far are roughly 900mm deep hitting chalk and flint. As they are only taking the weight of the flooring and no walls I imagine they won't need to be as deep. I know building control should advise however I would like to dig them tomorrow before they come on Monday and hopefully sign it off

Thanks,
Neil

 

[trowlerman]

Hello,

I'm currently digging my trenches for an extension. The only sections that are left to dig are for 2 internal foundations which will support the weight for a block and beam floor. These are quite awkward to dig long the side of my existing house.

My query is how deep would they need to be? The trenches I've dug so far are roughly 900mm deep hitting chalk and flint. As they are only taking the weight of the flooring and no walls I imagine they won't need to be as deep. I know building control should advise however I would like to dig them tomorrow before they come on Monday and hopefully sign it off

Thanks,
Neil

300 mm should be fine

 

[noseall]

The same rule applies to any load bearing foundation. Go down to good ground.

 

[Frank12345]

Hello,

I'm currently digging my trenches for an extension. The only sections that are left to dig are for 2 internal foundations which will support the weight for a block and beam floor. These are quite awkward to dig long the side of my existing house.

My query is how deep would they need to be? The trenches I've dug so far are roughly 900mm deep hitting chalk and flint. As they are only taking the weight of the flooring and no walls I imagine they won't need to be as deep. I know building control should advise however I would like to dig them tomorrow before they come on Monday and hopefully sign it off

Thanks,
Neil

As has been already stated if it picking up the floor loadings you should go down to good load-bearing strata. That could well be the 900mm you have gone down too for the main trenches. Sadly it is not for Building Control to advise, but to check you have done it correctly.

 

[noseall]

300 mm should be fine

Says who?