What type of walls should be used for the separation of duplex?

[dshall]

Does anyone know if plumbing is allowed to be ran within the party walls?

Basically, I have a 3 floor mirrored duplex, and the bathrooms of each unit are against the party walls. (the sink and tub)

Can plumbing be ran vertically within the party wall from upstairs to downstairs?
how about horizontally from unit to unit?

Of course you can but as Lew said there are some requirements for penetrating such walls.

[lgc30642]

Does anyone know if plumbing is allowed to be ran within the party walls?

Basically, I have a 3 floor mirrored duplex, and the bathrooms of each unit are against the party walls. (the sink and tub)

Can plumbing be ran vertically within the party wall from upstairs to downstairs?
how about horizontally from unit to unit?

You'll find the answer in the International Residential Code IRC-2006, 2009, Section 317, Dwelling Unit Separation as to fire ratings for the walls.

Your local Building Inspection department may have exceptions that you can use, but most counties where I have built follow this Code to the fullest, so don't proceed without checking with them.

When I have built duplexes or townhouses, we build one wall, drywall one side, fill with insulation material, apply second layer of drywall with overlap to cover the floor system, then proceed with the second wall with the 1" separation. We then build the second wall with it laying down, add the drywall on the 1" separation side---continuous for the depth of the floor system, then stand the wall up in its place. Do not forget to apply sheetrock mud and taping to the joints on the inside air space walls before lifting the second wall into place. You'll need plenty of help for this due to the weight, but you will have a substantially better built and fire resistant structure.

Voila, the inside drywall is now in place, and I don't need a skinny guy to do it. Then, build your other walls, add your floor system, and repeat on the floors above. You will need a liberal amount of fire-rated caulking to cover any gaps or spaces where layers of sheetrock meet that are not taped and mudded.

See Section 317.2 of IRC-2006 regarding the plumbing and vent pipes in the party/fire-rated walls. These are prohibitied in most circumstances, so you will likely need to plan for a separate furred out wall away from the fire wall.

Again, check with your local code officials--------------just as everyone else has urged you.