Hi All
One corner of the house I am starting is on solid rock about 1″ below the surface. I am going to have to form over the rock but pinning should not be required as it is a shallow slope.
Does anyone know of a system that will allow me to easily set up my footer forms? Can I rent the same kinds of forms used for walls and adjust the width.
My mason is not very familiar with footer forms so I may end up doing it myself. Any advice is greatly appreciated.
HC
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Concrete sticks pretty well to rock as long as its clean. I've never tried a power washer, just a brush and hose but its an idea. Scribe or block holes in the footing forms with wood, rocks, gravel..whatever. You just need to hold the concrete in place long enough for it to set. Pouring a stiff mix helps immensely. Vibration is optional. Once you have a level footing or sections of level footings to build on you're good to go.
I've had to form over bedrock a couple of times. My method is to hammer drill 1/2" holes into the rock and drive #4 rebar dowels into the holes on the outside of the formboard line to serve as stakes.
If you drive the dowels in 3 or 4 inches, (all you want is a little shear strength), you can twist them out with a pair of vise-grip pliers after you strip the forms.
Drive them much deeper and you may have to cut them off with a torch (depending on the rock, of course).
Might be easiest to form the sections over rock with 3/4 ply. Yeah, even formsetters have to scribe their work once in a while. Temporary pins to the rock or kickers out to the nearest dirt, depending on how far that is.
The easiest way i know of to form over rough surfaces is with a wall and tie ICF system like Integra Spec or even Lite Form if it still exists. With Integra Spec, you can form any thickness of wall in 2" increments from 4" on up. You can scribe the foam forms to the rock with a knife and a drywall saw. Kick them into postion, put a little dirt against them to keep them there and fill er up.
I'ld pin it. If it is on a slope, even shallow, I'ld pin the heck out of it. 2 rows of #4 12"OC.
SamT