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Important Points to Remember for Eccentric Footing, Cantilever Footing or Shoe Footing

July 30, 2017
Some days ago I have posted a Picture of an eccentric isolated foundation and I asked my fans on facebook that whether it is right to place an isolated column foundation like this or not?

As a result I have got some very useful and insightful comments of my fans which i though I must share with you on the subject of eccentric footing, cantilever footing or shoe footing.

After seeing this picture one thing is obvious that it is isolated foundation, but we mostly have columns at the center in the isolated foundation but due to property restriction and for keeping the rules of property line in the region such foundation is constructed but with proper provisions and following the code i.e. satisfying all the forces including shear and overturning moments. Which is not the case as such as far as my judgment is concerned. 

If you say this is completely wrong than actually this is not the case, as mostly in our cities where the area is restricted and the last column in the edges or in the corners they need to be placed on such foundations so that the columns can be hidden in the outer exterior walls without wasting the space. 

Picture from Ricardo Castro
Picture from Ricardo Castro
So keeping in view of this requirement one of our fan Ricardo Castro was of view that this is not completely wrong as sometimes you need to follow the property lines. 

However, there are some mistake in this as well; and we would like to quote some of the answers we get from our fans :- 

JD Orendain 

No strap beam? Thats just not right. The footing cant handle the moment due to eccentricity of the column. Property footings require strap beam so as to handle the moment and for the footing to act as a double cantilever footing.

Aquil Sohail 

It is right..This type of footing is called shoe footing....For this type of footing required more depth and heavy steel..I was cast like this type of footing on site .. Mostly use when space is very less ..

Engr Anwar Khan 

Its eccentric footing use mostly to the property line.if it a multi story builing need to connect with other footing such is strap beam/combine footing to avoid tilting of the footing. 

Mukassar Najeeb 

If load is less than no problem but provide a strap beam in footing equal to length of footing only no need to connect with another footing 

Mohamed Abd

 if it is a single.storied.building no.issue.but for a multisrotied building better to plant a column at the.eddge of.the.footing untill meet a strap.bram at the tie.beam.level 

Kunal Kutwaroo 

No blinding layer. No cover. No strap beam. Wrong

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1 comment:

  1. after completion of installation of addtional reinforcement with 16mm dia with 300 dia spacing rebar on site, the rebars dia was updated with 20mm dia in design drawings with 300mm spacing.
    what will be the possible addtional rebard to be added to make it equal 20mm dia bar strength with out removing the existing 16mm dia bar.( i prefered 12mm dia rebar in paraellel to 16mm dia with 75mm spacing each other i.e. for 16mm dia it will be 300mm spacing and 12mm dia also it wll be 300mm spacing).
    More important is that, Need to know the strength of 20mm dia can be equal to 16+12mm dia?? (as the area and wt: of 20mm dia bar and (16mm+12mm) is equal).
    waiting for urgnent reply.