I am clearing out the loft and want to lay chipboard over the central
portion. (This is a three bed 1950s ex-LA semi.) Part of the loft has
already been covered with 12 mm chipboard, which, while a bit
'springy' under foot, is after all only supposed to be walked over to
get from one side of the loft to the other. That is, no cheapo "study"
area or play area or something, but merely to stop me (or others)
putting their foot through the plasterboard (which I did do once, and
it was a real nuisance).
But 18 mm chipboard seems very heavy! At Homebase tonight I lifted the
corner of a 2440 x 1220 sheet, and I thought, boy that sure is a
weight to be adding to my poor old house!
One alternative I have seen used elsewhere is to use unplaned softwood
and space it out so that there is a one inch gap between adjacent
boards. Softwood isn't nearly so dense as chipboard, so it must be
quite a bit lighter.