In response to climate change, BRANZ (the Building Research Association of New Zealand) recommends that new houses or additions be designed for a higher wind zone than required, to safeguard against the effects of extreme weather events. The additional cost is not great for the peace of mind gained. I follow this recommendation in most of my projects and have done this for our home renovation and additions.
 
For further information refer to BRANZ Designing For Climate Change

Designing with future additions or alterations in mind is also important. A recent additions and alterations project incorporates a floor structure within the addition’s roof space for a future upper level as shown in the image below. This will not only make the future second level cheaper overall, but it will also significantly minimise waste and disruption during construction as the lower level ceiling can remain intact.

A floor structure for the future upper level was incorporated into this new addition’s roof-space

Photo documentation of all the walls and roof structure at framing stage (for future reference when making alterations, for example) is also recommended. This makes future location of framing, ducting, and wiring much easier.

Photographs can clearly show the location of pipes and wiring