Strip Footing Overhang for Constructability

#1

Easy one for my first thread. Long ago I was told that footings should overhang CIP walls 6" so that the overhang can serve as staging for the wall formwork. Is 6" really the minimum? Think 4" would do? I’m doing a bunch of high end residential where the geotech has specified a minimum strip footing width of 18". But the architect likes 10" walls (usually I go 8"). As a result, I’ve been making the strip footings wider than they need to be geotechnically just because of this overhang “requirement”. Feels wasteful…

c01

#2

I typically use 4" min overhang… wide enough to support formwork.

Dik

#3

For 6” walls I use 3” minimum. 12” footing

8” walls 4” min. 1’-4” footing

10” walls 6” min. 1’-10” footing

#4

I grew up working in residential construction, including the installation of many concrete basements. Our standard practice was to nail a 2x4 down flat on the foundation and set the forms on top of that. This gave us an easy surface to pin the base of the forms in place so they wouldn’t move as well as add an 1-1/2" of height so if we were pouring an 8’ wall, we wouldn’t be placing the concrete right to the top of an 8’ form. All that to say, 4" should be sufficient for placing form work. The “Symons” forms that we used were steel frame with wood faces and were 2" thick. Even going down to 3" would not have been a problem for us.

#5

When I worked for another company, the standard was to have a minimum 6" overhang on each side because 4" is too hard to form. I never got a complaint.

On a side note, I had a project where I specified a 4" concrete wall shotcreted into an existing rubble wall and the contractor said that it’s too hard to make 4", so I changed it to 6". Maybe it was a bad contractor. shrugs

#6

I have used 4" projection for years and never heard of a problem setting forms.

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