Can you install decking boards with the grooves up?

[#1]

The grooves are non-slip. You'll see a lot of people use grooves if they have a ramp or steps off their deck. However, the grooves are actually there for air circulation underneath the boards and manufacturers recommend you install your boards groove-side down. - Jackson

It should be grooves down. You might even void the manufacturer's warranty if you install them upside down. If you need a non-slip surface, then use an appropriate sealant or textured strips. The grooves should be face down as they are there for airflow and to stop moisture build up. If they are face up they will soon be full of grit and grime and algae etc and will become even more slippery. - AHoy

Just for some anecdotal evidence (the best kind), my brother-in-law (carpenter) has his ramp groove-side up and it isn't slippery at all. He has had no issues with rot or algae, and older relatives enjoy the extra grip. - Jackson

We recommend installing the smooth side up so that the rain runs off easily, helping to prolong the life of the deck and making it easier to keep clean. - stupidfish

[Ready2go]

the grooves of permapine do wear down and I've had to replace worn boards for clients.

Others have asked me to paint the worn grooves with non-slip paint for wheelchair access ramps. This is not recommended by any of the paint desk or trade teams at Bunnings.

5 minutes of Googling and you will find most people recommend the groves go down but also that it isn't critical which way they go

[MikeTNZ]

Just be aware that if you live in an area where icing/frost during winter, possible snow or hail may occur, the grooving can trap water

or ice in these grooves.

A good friend of mine had her collar bone broken when she slipped on the deck she had built.

Just something to be aware of when designing and building a deck or indeed anything that uses external timberwork.

Cheers,

Mike T.