"visionset" wrote in message
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"OG" wrote in message
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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.

Are you sure its a house and not a bungalow that someone has converted the
attic?
4" is not deep enough for floor joists over 11' imho