I want to lay tiles on an uneven asphalt floor. I have two different thickness of tile so thought i would build a wooden frame and use the one thickness within the frame first this i am hoping to use as a platform to level the second thickness up to the same height outside the frame. as i have never used bitumen i don't know how well my plan would work .I am concerned my tiles might start to sink if the bitumen is too thick is there a problem if its 15 to 25mm? secondly how do i go about heating up the bitumen do i use small amounts at a time does it go off quick. Once the floor is down i would need a floor sander to level the floor ? the tiles are mahogany 2x7inch by 3/4 inch the second thickness is 10mm