Walls – How to drill through rim joist/sheathing for a dryer vent

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I want to vent dryer through the rim joist of this home but it looks like this home has some sort of stone sheathing underneath the cedar shake. I can only see it from the basement. I can't really tell from outside without some destructive testing.

I am trying to figure out what this is, poking it with a screwdriver it appears to be hard as stone and would quickly dull my hole saw. The sill plate is atypical too. It looks to be more like a 4×6 with the floor joist notched and resting on it. There is room above this beam for the dryer vent but I don't want to open a can of worms.

The foundation is 24" thick feild stone.

Any idea what I have? Could it just be plaster?

EDIT:
Picture attached. I was wrong, there is no room above the beam. Above it you can see the hard material. Either way, I'm not sure I want to drill through the thick sill plate beam now.

enter image description here

Best Answer

Your house is more than likely Balloon Framed. Stick and Platform framing hadn't come into being in 1900. In a balloon-framed house, the studs you see in the basement run all the way up to the roof. The filler material is a concrete mixture that was used as a partial fireblock and also to hold the spacing of the studs.

You can put a hole through the concrete using a 4" coring bit and a coring drill. Google for "coring drills rental" and you find plenty of places that rent them. Your local home center probably does, if they rent tools.