Size of Screws please help

Hi, 5kgs is a fair weight and I’m sure you don’t want to recreate Only Fools and Horses! If you use screws (No8 1.5” or 4mm x 40mm) Into the wooden plate, this is relying on the screw/wood thickness to hold. Without knowing the condition of the plate, you will not know how good the fix is. Can you get above this plate from the floor/room above? If yes, then I’d suggest an M6 or M8 washer and bolt fixings. 3 or 4 quantity. Pilot hole first. I’d would be concerned though, that a competent builder cannot decide on a suitable fixing!

I would agree with Archer furniture but add stress to checking the ceiling. I would put in a test hole from below if you cant get above it. Your main issue is really what you screw in to as most screw sizes will take 5kg no problem at all, but the biggest bolt wont hold plaster for long!

If it is a heavy chandelier you will need to use 2" 10's screws

I would agree with existing answer , especially the one with a builder not knowing what screws to use or a solution. I would definitely recommend to up lift floor upstairs to see if u can get a good fixing . If it is near or next to an existing floor beam then make up noggins so u can get self tapping hex bolts into wooden joists, any good builder should know this . Hope this helps. Do a job properly so u don't pay twice or damage an expensive chandelier. Matthew sutherley Total renovations