danih – The owner appears to have made several demands.
An OC is required to undertake repairs to the common property but they do not need to follow the dictates and/or demands of the owner.
An OC can arrange for an independent assessment of the need for repairs, and can arrange for a competent trades person to undertake the repairs.
If I was you I would have a competent builder look at the areas of concern rather than employing an engineer. Ask the builder whether he thinks that an engineer’s report is required.