I have a large solid teak parquet floor laid on a concrete base in 1963. I have just removed carpetting covering the parquet and discovered that there are large areas of loose tiles where the concrete has sunk and cracked.. Initially the tiles were laid with bitumen. The parquet consists of small tiles 115mm x 23mm x 9mm in batches of four. What do I do with the hardened bitumin on the concrete base and tiles to get a level surface after filling in the cracks.. 1/ do I use a hot air gun to melt the bitumin and press the tiles in to place 2/ do I try to remove the bitumin which would involve a great deal of hard work and would involve prising up more tiles than necessary. 3/ do I get in the professionals. guidence please