I'm preparing to install laminate throughout the first floor of my house and have discovered some issues with the existing fooor. I have a porch converted to living room with a subfloor that meets the original hardwood 1/4 inch high. I was going to sand down the edge to about 1/8 and then flash the difference. My tile man father in law wants me to use fortified thinset with acrylic admix to do this. Also, I have some concave areas that dip up to 1/4 inch over 4 ft. diameters. Any thoughts on my choice of flashing or any other suggestions would be great.