This primarily depends on the location of the decking, followed by personal preference.
The New Zealand Building Code requires that decking on the main access route to a building must have a slip resistance of 0.40. Grip tread timber decking will conform to this requirement.
If not on the main access route then the decking can be installed smooth face up.
To help you make an informed decision, I list below the pros and cons of each option:
Grip Tread (Grooved Face) Up
Smooth Face Up
Be aware that many manufacturers grade the best face of the decking on one side (normally the ribbed face) so you will need to check what face has been graded in advance. You may not be able to reverse the decking without exposing some defects on the back face.
Abodo Timber Decking is available in both smooth and grooved face graded options – unlike most suppliers. The ribbed profile is a modern take on the classic decking groove, with a subtle groove that wears evenly.
So go ahead, choose the option that suits you best, and ensure you are getting the best face up.
Daniel Gudsell, Abodo Wood Ltd