New party wall for splitting old house

[tom ash]

The house is an old cottage with flint and lime foundations. we're splitting it in half on either side of an old inglenook fireplace. Ive stripped out the floors and ceilings etc so we've got a clear space floor to roof. I'm trying to decide on the party wall construction. I don't think fire proofing should be a problem but I'm struggling with the 45db sound regs.
My problem with a masonry wall, is that I'm nervous about digging around the foundations/chimney in case I destabilise anything.
Id prefer timber but am finding it hard to find information on sound proofing, the internets full of people trying to sell you stuff. Building control refered me to the shefield insulation group but they were worried about giving advice.
Also theres a lovely round window in one of the flanking walls which cuts our width down to about a foot.
Anyone have experience with building timber party walls. two story. vaulted ceilings, all the way up is about 5metres. I can include joists or strengthening at the first floor level.

 

[freddiemercurystwin]

There's a timber example in the Building Regs Part E, which you should be looking at anyway! Or the Robust details which I think the Building Regs example is taken from or is based on: http://www.robustdetails.com/the-handbook/selecting-your-robust-details/timberframe-walls Speak with your BCO and tell him what you're proposing and get his agreement before you commence.