On Sep 20, 8:38 pm, Owain wrote:
Cicero wrote:
Google pictures suggest that it's on castors which in turn suggests very
localised loading. It would be worth considering some kind of load
spreader made from material other than wood which can't be
easily penetrated or indented by pressure.

I'm slightly more concerned about the point loading too. I think I'd be
inclined towards thickening the floor rather than the joists.

If belowfloor supports are used, it might be worth recessing polished
metal plates into the finished floor to (a) spread the load, and reduce
indentation into a soft floor, and (b) indicate the correct location of
the piano feet.

In fact I face a related problem. I plan to put an upright piano into
our 1960s house and the position it will occupy means that all the
weight will be one two joists running parallelto the piano. the
joists in the house are inadequate; I have alrady had problems with
the floor moving when I piled a lot of books on it, so I plan to add
some supports under the floor first. i was going to support the
centres of all the joists by wooden struts up from the ground each
standing on long planks placed on damp-proofing membrane placed on the
ground. Adjustment would be by carpenters wedges hammered together
and then nailed. I woul ddo the whole floor, to reduce the
pringiness, not just the two joists under the piano.

In my case it is the springyness that is the problem, not the danger
of collapse.

R