W
White Room
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Not wanting to throw a spanner in the works or anything but are you sure its solid concrete under the bitumen. If its an oldish coucil house it could be magensite.
These screeds were very common in council houses from early 50's to mid 80's and were often coated with a bitumen topping to keep moisture out cos they become very unstable when wet. They are a complete Bu**er to stick anything to cos of the high levels of chlorides in them. They are no longer considered suitable for floors to receive floor coverings.
Identification is relatively straight forward - they are usually a pinkish or greenish hue but this colour will be masked by the bitumen. They are electrically condictive so if you use a resistance type damp proof meter you will get an off the scale result for damp even when bone dry. If it is magnesite best thing would be to take it out and relay with something else.
Hopefully you are right and it is concrete.
These screeds were very common in council houses from early 50's to mid 80's and were often coated with a bitumen topping to keep moisture out cos they become very unstable when wet. They are a complete Bu**er to stick anything to cos of the high levels of chlorides in them. They are no longer considered suitable for floors to receive floor coverings.
Identification is relatively straight forward - they are usually a pinkish or greenish hue but this colour will be masked by the bitumen. They are electrically condictive so if you use a resistance type damp proof meter you will get an off the scale result for damp even when bone dry. If it is magnesite best thing would be to take it out and relay with something else.
Hopefully you are right and it is concrete.
D
Derry
hi, welcome to the forums 
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