If you are wondering how much a Yamaha U1 weighs then hopefully I can help. From what I can gather it seems to be around the 230kg mark.
Dawsons website claims 228kg
UKPianos.co.uk claims 228kg
Roberts Pianos has it at 310kg
Melvin Besbrode from Leeds has it at 228kg
Sheargold and Markson Pianos both have it at 228kg
The Pianoman Ltd also lists it as 228kg
Countrywidge pianos also have it at 228kg
So I think it is safe to say that Roberts Pianos have made a typing error and that the correct weight of a Yamaha U1 is 228kg.
Will it fall through the ceiling?
If you place this piano upstairs you won’t have any problems with it falling through the floor unless you have a seriously week house. The weight is shared out across the 4 castors so you should be fine. If you are in any doubt then of course you should get a builder in to do some tests and give you his professional opinion on whether the weight will be an issue.
OK, I hope that helps. Please see my other FAQ Articles articles in case they are of interest.