Lisa,
I don’t have personal experience of this, but I don’t believe it should be your Strata’s responsibility to pay either.
IMHO, Clause 2 of the approval conditions takes precedence over the other conditions as it appears earlier.
Also IMHO, the Strata should not necessarily be involved (in the dispute), as the lower owner can take the higher owner to the CTTT in their own right.
However, there does seem to be some confusion over the standards.
Impact Isolation Class (IIC).
With IIC the higher the number the greater the sound isolation effect. A good IIC standard is 60. 70 is excellent but not realistically achievable with timber, parquetry, ceramic tiles, marble or stone flooring.
Ln, Tw +c1 (whatever that means).
With Ln, Tw +c1 the lower the number the greater the sound isolation effect. A good Ln, Tw +c1 standard is 50. 40 is excellent but not realistically achievable with timber, parquetry, ceramic tiles, marble or stone flooring.
I think one measures attenuation and the other measures transmission.
The SM specified IIC of 69. That’s good. Just like carpet.
The upstairs owner is not entitled to demand, especially post-installation, that they “should have been given” a lower standard.
Or are they just confused about the two standards?
Anyway the SM gave correct advice.
And the By-Laws (against noise) take precedence.