On 28/12/2013 18:25, RJH wrote:
I'm about to lay laminate flooring in a ground floor room. Room has a
suspended timber floor with cellar beneath. The existing floorboards
are tongue/groove in reasonable condition. The cellar isn't bone dry,
but is well ventilated.

I'm going to lay the laminate over fibreboard, as the existing floor
isn't snooker table flat, but well within 3mm/1m. Should I use a
polythene sheet dpm between the fibreboard and the existing floor? I
can't fully get my head round whether it's better to allow an
element of 'breathing' (no dpm) and risk damage to the
fibreboard/laminate. Or protect the fibreboard and risk damage to
the sub-floor. This thread sums it up:

http://www.diynot.com/forums/floors-...boards.344586/



So, DPM or not?!


As things stand, the moisture content of the joists will be around 20%
average I would think, and the top side of the floorboards probably less
than 10%. It's anyone's guess whether the laminate will be more affected
by the cellar conditions or those above floor level. On balance I think
I'd go with the dpm over the fibreboard, or toss a coin :-)