IMM wrote:

To prevent impact sound travelling through, have the ceiling on the ground
floor on the existing joists and the floor above on the TJI "I" beams. Do
not have the "I" beams touch the existing joists or the ceiling below. Fill
the void with Rockwool bats tight up against the "I" beams.

Nice trick if you can do it. What I found was that to insert the new
floor joists, I needed to cut away tie beams that run perpendicular to
the original joists. These were typically placed in the middle of the
span of the longer ceiling joists to give lateral support and also to
spread the load of the ceiling over several adjacent beams.

To stop the ceilings sagging when you cut through the ties you need to
replicate the function of these beams. The usual way to do this is to
add noggins between the new joists that can be fixed to the old ceiling
joists to brace them. You also need to make sure that you strap each
ceiling joist to something solid before you take out the tie beam, and
until you have fixed it to the noggin.

The down side of doing this is you now have a point of contact between
the floor and ceiling joists.



--
Cheers,

John.

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