Merbau is a good choice for weather-exposed situations. It is relatively stable and rot resistant. If you are replacing an existing verandah floor no doubt you are familiar with the hazards associated with using t & g flooring in such locations, eg. possible swelling of the timber if rained upon, corrosion of fasteners, etc. It's important to not cramp the boards tightly together, and to apply a water repellent finish such as decking oil.
MerbauAnswered on 05-03-2021
Please note that our answer is based on the best advice available at the time. If the National Construction Code, Australian Standards or local requirements have been subsequently amended, our answer may no longer be correct in all details. For more information, please read our disclaimer.