Shimming Floor Joists

Hi all.

My 1st floor bedroom floor is wonky. Drops unto 40mm from edge to centre - looks like bowed joists. I'm loathe to sister each joists with new timber and someone suggested just shimming the joists - add a strip of wood to the top of each joist with varying thickness to create a level floor.

My concerns:

1) Is that an acceptable remedy?

2) Where would I get such long / thin strips of wood? I assume I would need various thickness as the joists will not all be bowed my the same amount?

These strips would need to be 7cm wide, unto 350cm long and between 1cm and 3cm thick.

Much appreciated in advance.

Bump?

I assume the bow of the joists is not totally uniform. To cut shims/fillets to individually match each bow would be a PITA. Far easier to fix some long straight wood to the joists...... sistering. The new wood doesn't have to be the same size as the joists, just big enough to take out the bow and have a good fixing. That's the way I'd go.

I once glued shims on and used an electric plane to take them down, with aid of a long straight edge. MONUMENTAL PITA.

Why are you loathe to sister the existing joists? If the floor is t&g chipboard with carpet on top, for instance, I would sister, deffo.

Why do you need 7cm wide shims, that's a lot of planing (if you go down that road)

What is the composition of the existing floor, joist ctrs etc?

Went wuth sistering in the end guys. Took the whole floor up and it was the only option.

Thanks!