In article ,
"brugnospamsia" writes:
I am now faced with two non-level, bouncy and bendy upstairs floors and
given that the downstairs ceilings also need replacing, I am wondering if
this is the best solution here too. The under-spec. joists run front to back
and are (loosely) cemented in to the outside and stairwell walls so the
replacement joists would have to be attached to wallplates and hangers. I
plan to use 22mm t&g chipboard in anticipation that most buyers in my area
tend to want carpet or laminate upstairs rather than sanded boards (I plan
to have carpet upstairs and sanded boards downstairs).

My brother had a similar situation with a bouncy floor.
When he was getting a full-sized grand piano (he's a
musician), we all had concerns about the floor strength.
He had the floorboards taken up, and new joists added in
between the existing ones. Then the original floor was relayed.
In his case, the downstairs ceilings had all been replaced
a few years before, and further replacement was avoided,
although one or two minor repairs were required where the
odd plasterboard nail had shot out when the floor was being
nailed down.

--
Andrew Gabriel