Stucco houses crack, that’s a fact because of the rigid nature of the material used and movement in one way or another. Addressing those cracks also becomes a question that I get quite often and I thought it was time to write about the topic so you know what the main options are.
To create holes, use a brace and bit to drill through the flooring, and then a keyhole saw to widen the entrance. Make sure that the holes are not exactly above a floor joist when you drill them. In fact, the joists & studying must be spared as much as possible while installing the water heater equipment.