different type of floor levelling question

[scubabob]

i have a mixture of floorboards through most of the house, some very old HW, some newer pine and some yellow tongue where its all been replaced. that's ok because i am putting new carpet down. Problem is, now i have ripped up the old carpet i can see different levels in the rooms. What i mean is where the hallway meets a bedroom, the bedroom floor is about 10mm+ lower than the hall floor. This is going to cause a nasty ridge so whats the best stuff to use to feather the edge over? Sanding it smooth isnt really an option. A carpet chappie i know said some use concrete but it tends to break after a while. i would prefer something longer lasting.

[Pusser]

Just a thought - would two layers of underlay make up the difference? I think 10mm is the allowance for underlay.

[echnidna]

Masonite underlay is the best way. But if you want a stable filler use Agnews Water Putty, sets hard quick and is waterproof too

[Dirty Doogie]

I Second the motion to use Agnews water putty !! Great stuff !! Available in 5 kg (I Think) tubs from Bunnings - about $40.