Do new 9x2 joists require lifting to stop bounce?

[MGPD]

I'm fitting new 9x2 joists in my loft and have been advised to lift them an inch from ceiling to stop bounce damaging the ceiling.

I'm screwing the new joists into the old so if they are going to bounce they'd bounce at the old joist anyway, wouldnt they?

 

[freddiemercurystwin]

I have always specified that the new structure for a loft floor be separated from the existing ceiling joists to avoid the bounce/sag of the new floor ever affecting the existing. Why are you fixing the new to the existing?

 

[MGPD]

I have always specified that the new structure for a loft floor be separated from the existing ceiling joists to avoid the bounce/sag of the new floor ever affecting the existing. Why are you fixing the new to the existing?

If I use 9x2 joists seperate from the old, will i still need to lift them from ceiling level to stop bounce ?

I was going to run the new 9x2s alongside nailing in to the old, each end sitting on a supporting wall.

 

[freddiemercurystwin]

I was going to run the new 9x2s alongside nailing in to the old, each end sitting on a supporting wall.

Why attach them? And nails will certainly shake your existing boards loose, if lath and plaster there's a fair chance great chunks will fall off if not the lot.

 

[steveuk]

Every loft conversion i have done, the plans have always stated that the new loft floor is totally independant to the existing ceilings

Steve

 

[tony1851]

Every loft conversion i have done, the plans have always stated that the new loft floor is totally independant to the existing ceilings

Steve

But how is the existing ceiling then supported?

Most ceiling joists tend to run on to the central brick wall between the bedrooms. They are usually 3x2 or even thinner, and are often supported mid-span by rough hangers nailed up to the purlin. Once these hangers are removed, the c/joists are effectively spanning wall-to-wall (11-12ft?) and may then sag a little under their own weight.
I take the opposite road and fix the c/js to the new joists (screws, not nails).
If the new floor joists are properly sized, they won't affect the ceiling.

 

[catlad]

You can still keep it independent if you keep the ceiling hangers behind the dwarf walls.