Foundation Design 2

[Aussie Dave]

Hi All,
I have a two story house seperated by a party wall and I am working out the foundation sizes for the properties before they are built. I have a ground bearing strength of 100KN/m^2, so I have calculated the party wall to be taking a load of 60kN/m^2 on either side of the party wall. Does this mean I need to calculate the foundation as either
(120kN/m^2 /100KN/m^2) = 1.2m wide foundation because the two houses share the same foundation or should I use 60KN/m^2 / 100KN/m^2 = 600mm standard strip foundation?

 

[ooox]

Your units are inconsistent, the party wall load should be in kN/m so you need to multiply the 60kN/m^2 by the tributary width on each side of the wall. The footing width would then be calculated by diving the allowable soil bearing pressure by the wall line load. If the 'ground bearing strength' is the allowable bearing pressure then you wouldn't factor your wall loads - check with your Geotech.

 

[Aussie Dave]

I meant to say the party wall has 120 KN/m on my wall, so my calculation is 120KN/m / 100KN/M^2 = 1.2meters wide strip foundation.

 

[ooox]

It would be 100kN/m^2 / 120kN/m = 0.833m.

I would make it a 900mm wide footing assuming this can accommodate the total wall assembly and allow for some tolerance.

 

[jayrod12]

Aussie Dave has it correct. 1.2m wide footing. 999's calc if you look at the units only is m^-1.

 

[ooox]

Sorry, you're right Jayrod...still haven't had my coffee yet

 

[jayrod12]

No one's perfect.

 

[PEinc]

Aussie Dave, although it was not indicated, I assume that your load on "either side of the party wall" also accounts for the weight of the party wall.

http://www.PeirceEngineering.com

 

[Aussie Dave]

Yes it does.