On 2016-05-15, Steve Walker wrote:

On 15/05/2016 22:27, Adam Funk wrote:
On 2016-05-15, Tim Lamb wrote:

We had a similar situation where dormers had been added to a bungalow.
The existing loft floor joists were probably 7"x2" and the new floor
joists 9"x2".

It would have been much better if they had bolted the joist pairs
together as loading the new floor tended to ping the plasterboard nails
off the downstairs ceiling.

Also done where there is a load such as a cold water header tank.

AFAICT, the ground floor kitchen & 1st floor bathroom were built at
the same time as one offshot (on a mid-terrace).

I'm reluctant to go back & take more measurements because I'd have to
clean the dust out of the kitchen again!

Is it only the bathroom or all upstairs floors? If all, could it be to
decouple the floors and ceilings to reduce noise transmission?

It's only in the offshot (bathroom above kitchen). I don't think they
worried about "advanced" things like noise through floors when it was
built.