One more foundation question. Who's telling the truth here?

[Stain]

I tore down my 20 x 20 garage in order to build a 28 x 26. Most of the foundation will fall outside the original footing. One contractor said he just needs to knock the footing flush with the ground. The other said he needs to completely remove it. I live in Michigan so frost heave is an issue. Is it really necessary to completely remove an old footing?

 

[Shocker]

It would always be best to remove the existing, but sometimes it is cost prohibitive. To pour a slab over an existing slab, especially if it is uneven or fractured, will cause weak points in the new slab for various reasons. If you're going to do it anyway, try to make sure the new slab is minimally 3" thick at the thinnest point of the formed area. Commercial solutions are available also to aid in the adhesion of new concrete over old. These products are available at most home stores.


That is not me. It is a quote from a concrete contractor.

 

[GeorgiaHybrid]

If the old footing is pulled out, make sure that the fill is compacted in layers until it is up level with the existing undisturbed soil. A hand held vibratory packer is what most contractors use for this in small areas (looks like a powered pogo stick with a plate on the bottom). You ideally want all of the soil under the slab to have the same compaction percentage to prevent voids later on and possible cracks in the slab.

 

[Stain]

Well. Thanks for the replies. Our city code requires that you fully remove the footings. We'll have to pack down the fill to prevent voids, etc. More soon.