Fibrocement nails letting go?

[MattWright]

G’day all
I am a new member and this is my first thread, I would just appreciate some input as to way some fibro soffit nails (about 30mm) have started to let go, you can pull them out. I have pulled a bit of fascia off and the timbers look fine (70x42mm ish hardwood) I THINK it’s Batu. The building is about 20 years old and the battens are spanning 3 ½ meters (far too much in my opinion) consequently they are sagging about 20mm <O></O>
I told the client that it could be because the underside of the batten has stretched (from the sagging) and its grip on the nail has let go…. I am reading too much into it?? What do you guys think?<O></O>
Thanks for your time.

[InterTD6]

some timbers will not have the same fastener holding strength from green to seasoned, I would say its from the timber shrinkage more than sagging.
regards inter