Concrete removal (metal tools)

If you are renting, consider one of the concrete chain saws since they are capable of deep plunge cutting and getting into tight areas. Typically hydraulically powered from a remote power pack (gas or electric) making the saw unit very compact.

Goggles, a 1/2 hp drill, a masonry bit, a cold chisel, a heavy steel mallet (also useful for quietly dispatching rivals in love triangles), and a grinding wheel to sharpen the bit and chisel as needed can get the job done, along with a lot of labor. My father buried a drain line from a humidifier under about 15' of our basement floor slab that way. There was no rebar in the slab, there might be some in yours.

Oh, he also had my older brother to do the grunt work, that helps too!

I'm having trouble visualizing exactly what this is supposed to look like when finished. It sounds like you want an 8" wide stepped 'ditch; centered under the door. WHy? Is there some reason why you shouldn't just cut a 2" wide thru slot directly under the door, fill it with extruded polystyrene or polyurethane foam insulation and top it with a strip of treated wood?

I'd probably just throw down some doormats on the cold spot.

The Idiot contractor was me, it was the 1st (& only) house I built so I was a newbie ;)

I would cut the concrete outside & inside the door and repour as needed. Or else just cut it as best you can and bust out the rest with a jackhammer and patch in the broken out areas after you get your door squared away.

GWE

Cut the concrete with a Harbor Freight diamond blade mounted in a 4" grinder, a 7" grinder, or a skillsaw. Get the 'Turbo' or segmented style, they work better in a free hand mode. You don't need to go all the way through, half to 2/3rds of the way is fine. The 4" HF blades are

Break out the rest with a sledgehammer. Clean up with a cold chisel or a $6 air hammer from HF.

Lowering the sill means that you will need to remove the whole frame and remount. If you think you can just lower the sill, use the diamond wheels mounted in an angle grinder to do the horizontal cut.

Nick Hull wrote:

I'll have to look into that, it might be a better approach.

I'm not worried about the floor being cold, I'm more concerned about the heat transfer to the whole house (both winter and summer).

Professional coring and cutting companies have large flush cut saws. Such a saw could be used to cut the strip outside in front of the door. You'll have some overcuts, probably quite long since these saws have large blades, at the ends parallel to the walls.

I'm not sure I understand the dimensions of your sill cut, probably a typo, but the sill cut could be made with an old circular saw that you don't care about much. Just use one of the diamond blades from HF or Home Depot. You can anchor a guide inside the pocket (where you plan to remove the 1.5")to get straight cuts. Removing the 1.5" pocket is, however, a dirty job that can only be done with a jackhammer. I use a rotary hammer drill with hammer only function and chip it out. You might want to run some saw kerfs across the pocket to help out, but mostly it's just chipping concrete down on your knees. Good job for a college student needing a few bucks on a Saturday.

Once chipped, the pocket can be patched with an epoxy based patching compound. I use a product called Shep-Patch, but it's called that because it's a house brand of Shepler's, a local supply house.

Mats on the cold spot will reduce heat trasnfer.

Just a note that respiratory protection is a must as well. Silicosis is bad news and a saw will generate a buttload of fine dust--wet sawing is better if possible.

I would worry about one clean, full depth or deep score cut inside and one good cut outside. Jackhammer and remove plenty. I assume you can change grades enough to step down from the finish floor level and not have water problems. You can dowel to the floor cut and the drive cut, use red wood or expansion joint material to form the separation at the outside building line.