"OG" wrote in message
...
I've just had to cut out and replace a section of chipboard type
floorboarding that had started cracking up and pulling away the T&G (for
some reason the join line was not ON the joists, but just off them. On
cutting out the failing section I found that the floorjoists had a crossed
couple of battens between them.
http://www.astd60.dsl.pipex.com/UnderFloor.jpg

Difficult to judge the scale but that looks like a heck of a deep void. Mine
are only 4". I suppose it is dependent on the spans, my max is ~11ft in a
1930's house.

--
Mike W