Im due to have a wood stove installed in my fireplace. The person doing the site visit thought that the base hearth is damp and suggested redo it. I have never done it before so I'd appreciate some advice. THe way i thought of doing it is to dig up the cracked top portion of the hearth, lay a DMP and recast the hearth. Is that the way to do this? What's the sand/cement ration for this kinda job