How do you add a footer to a carport to garage conversion with walls already in place?

Question:

I would like to know how to fix a carport to garage conversion that was done without permits and has no continuous footer? Is it possible to add the footer under the slab while keeping the slab relatively intact?

Answer:
Hi,
Thanks for visiting all-concrete-cement.com and thank you for such a great question.

This is a relatively simple fix but is no easy task for sure. Understanding the existing load is very critical in determining what steps to be taken to ensure the integrity of existing structure is not compromised.

The loads are concentrated at the existing posts which means they must be protected during the work. If you want to install continuous footings at perimeter, you can leave at least 3ft around the existing post undisturbed while you dig the footings in areas between the posts.

You can dig the footings in two ways: First and most expensive is to saw cut the existing slab at least 12 inches from edges and dig down 30+ inches if you're in area subjected to freezing or 18 inches elsewhere. This is most expensive because of the cost of saw cutting.

The second option would be to dig down at the side of the existing slab and chip down below the slab, letting the slab cantilevered 12+ inches. You can then pour the new footing to come beneath the existing slab. If you want, you can extend the new footing upward in the form of curb wall to come above the slab where you will build the new wall. This can only work if the soil is not sandy.

Whether you use the first option or the second, the existing posts must remain undisturbed. If you want to replace the posts' footings simultaneously with other areas, you must bring in temporary posts to shore up the existing post while the work is done.

Here is something to think about, the fact this carport had been in place for who knows how long tells us the continuous footings are not required for the carport soon to be converted garage. It also means any wall you're going to build will only help the strength of the new garage.

If I were you, I would build the walls directly on the existing slabs, tie the top to the existing beam that transfer the load to the post and be done with it.

Those slabs are good enough for SUVs to drive and park. They are certainly good enough to support walls that support much less load than the weight of an SUV because the loads are carried by the posts.

I hope this helps
Good Luck