Wall foundations

[1806mill]

Hello

I'm planning to build a 9 metre long by 600mm (250-300mm thick) sandstone wall between two existing sandstone structures. The subsoil is a stable mixture of gravel and sandy soil.

My question is how deep a foundation for the wall should be, and should it be hardcore/cement or just a long poured cement 'block'. If anyone can help with their experience/knowledge I will be very appreciative. Thanks.

 

[ian413]

As your wall is 300mm wide the foundation should be wider than the wall, I'd personally make it 500mm wide or if you are using a mini digger, then just go by the width of its front bucket. ie 450mm but that will dig a roughly 500mmm trench anyway.
Depthwise at least 500mm should be ok. however the top level of the concrete should be approx 2 courses of brickwork below the existing ground level. So in reality you will be digging 500mm + 150mm in total.
A proper mixed concrete foundation is best. Not sure what you mean by 'cement block'.
The total amount of concrete needed for your foundation is LENGTH*WIDTH*DEPTH-9m*500mm*500mm=2.25cubic metres. This is a fair bit to mix yourself, so look into a Mini Mix concrete supplier. Plus you could just say what the concrete is being used for and they would recommend a concrete strength.
Hope it goes ok
ian

 

[1806mill]

Thanks Ian, I'm glad I asked the question now.

 

[joe-90]

In my opinion that foundations is way over the top. 'Noseall" gives a good foundation in the building forum.

 

[ian413]

In my opinion that foundations is way over the top. 'Noseall" gives a good foundation in the building forum.

Way over the top?? In what sense?? The foundation needs to be wider than the wall it is carrying and the depth of 500mm is a minimum.
We dig a 500 trench as standard at work and there is no need in doing any less cos it could all go horribly wrong, plus I didnt want to tell him any shallower just incase.With a 5oo mm depth you have piece of mind,no need to go any less as you might regret it in the long run...

 

[joe-90]

A wall 600mm high doesn't need a 500mm foundation. I've seen Victorian walls that have no real foundation just a course of extra bricks underneath. They are still there 100 years later.