allan tracy wrote:

I have a friend who has just bought a semi-detached seventies built
property. The house was constructed to the nowadays pretty standard
timber frame method.
Is this the type of property which has timber frame /plasterboard as a
party well between the properties also?


No, it appears to be some sort of brick possibly breeze block.

He thinks it's only single thicknees though as it's visible in his loft.

finally you give us the info necessary to answer the question. The
solution is probably a 2nd block skin not connected to the first,
preferably with loose fibre fill between the 2. Lesser but still useful
levels of attenuation can be gained with a metal frame stud wall, which
takes less space and materials, instead of the 2nd block skin.

However, one must ask what is the path of most sound transmission? It
might be holes below the floor rather than through the block wall.

There are also ways to stiffen suspended wood floors, such as fitting
noggins or converting to stressed box construction, which is fairly
easy to do.


NT