floor joists and flooring

[climber101]

Hi,

I have 150x50 flooring joists currently specified for my ground floor extension, these will be over slightly less than 3m span. I am looking at putting in an upright piano which i have helped move before and whilst i don't know how heavy it is it is ** heavy (older style). How bombproof is 150x50 at this span please ? and also i have 22mm "chipboard" specced any suggestions of a stronger flooring - is there any pros/cons to using plywood or marine ply or is there a more common type of stonger flooring matl.

Thanks again

 

[Shytalkz]

They are ok sizewise for general domestic use at 400 centres; bit over on both stress and deflection at 600.

It really depends on how heavy this thing is and where on the floor you intend to place it; obviously, the best place is not in the middle of the floor! If you're worried about the floor deflecting significantly, or getting noticeably out of level, lift the chipboard and put down 18 or 22 ply, screwed down to each joist with 75 long #10s at 100 centres coming in 1m from the supports and 300 centres for the middle bit. This has the effect of making the floor a series of Tee beams all joined together and is much much stronger than the usual chip deck and joist arrangement.

Try it on the floor as-is first and see how it behaves, which will save you doing the strengthening work for no reason, if it all performs ok.