Acoustic insulation that's tough enough to shove under floors?

[Sparrowhawk]

I've got a few places (up to 1m deep) where I can't lift the floor to fit acoustic insulation as stud walls and plant are already in place.

 

The stuff I bought (Knauf Acoustic Roll) is too fluffy to be able to shove horizontally - it bends, tears and refuses to cooperate.

 

What's going to be best to insert here? Rockwool Sound Insulation Slab or similar?

[crispy_wafer]

I was using the knauf stuff in ceilings but ran out with a few sections left.  I purchased some Ursa APR to finish off.  It's a lot more rigid, but it's also not the nicest stuff to handle.  RWA45 is also quite rigid.

[saveasteading]

Acoustic roll is just a few dB better than thermal insulation, so use any that will stay in place.

Have a look at Knauff Dritherm 

[ProDave]

Frametherm 35 is quite stiff.  I left this test piece for 6 months without any support and it did not budge or slump.  But I would want something under it to support it.

 

[jfb]

Rockwool r45 (I think it is called) will friction fit if cut right

[saveasteading]

48 minutes ago, ProDave said:

Frametherm 35 is quite stiff.  

I meant frametherm. Easy to cut to shape, and springs to self support, and squeezes into corners. 

 

That will catch airborne sound but not impact.