Decking - grooved side up or down?

[Donno]

Hi all

I am going to build a deck which will be coverd to some degree but may get wet in some areas. What I would like to know is whether the grooved side of the decking (treated pine) is layed on the upside or are the grooves meant to be on the underside screwed to the bearers?

I have asked this question of the timber supplier and others but I am getting conflicting advice. If anyone knows and knows why the grooves are one sided only, it would appreciated if you could tell me.

Thanks in advance

Donno

[Brown Dog]

hey Donno

As far as I know the grooves go down to allow a bit of ventillation to prevent rotting between the decking boards and joists. Not up to provide grip as some may think.

cheers Paul

[silentC]

If you want to look like you know what you are doing, put the grooves down. If you want to look like a dill, put them up. Simple really

[bennylaird]

Definately down. Would I lie?

For the reason above, to stop the rot.

Always tell the amatuer job when you see them laid grooves up.

[bennylaird]

Mental Note!

Avoid any advice from those who told you grooves up.

[silentC]

But don't take my word for it.

[echnidna]

They are desinged to go grooves down

BUT

Grooves up is less likey to become slippery so there is sound justification for grooves up.

[Old Codger]

Well I have put them up both ways depending on where they are. If they are on the southern side of the house and liable to stay damp or icy then I put them groove up. If they are on the northern side and the client wants to paint them then I would put them smooth side up. I have built acsess ramps that always have the groove up and running across the slope. I wouldn,t do them any other way. If you are worrying about the dampness in a joint then why dont you groove the top of the bearer or the bottom of the joist or any other of the countless joints in a deck. Most decks are treated pine and should be able to stand being damp. If the smooth side was the face then the ripple side would be on the outside of the pack when they are delivered. Not so.
I have never seen a deck that that was only rotten on the joists and no where else.
Usually a deck fails because the span of the decking between joists is too great and a knotty piece of decking breaks or people use materials that cant stand beinmg in the weathewr for long periods.(ie tasoak)

[David L]

If you put them grove up they hold water and channel it along the board
making a bigger mess and harder to dry= rot

[Old Codger]

Treated pine doesnt rot.
We often put in paths with a steel float finish in the old days, now its all broom finish. Wooden decks can get slimy on the damp side of houses.
I advise clients to have the grip side if the deck is likley to stay damp.

[Bluegum]

I've seen decking with the grooves up and covered in slime and having to be replaced due to not being able to dry out properly. I am now thinking its much of a muchness as to which way it goes.

[Bleedin Thumb]

Find out if the treated pine they are going to sell you is LOSP if it is go hardwood because I wouldn't trust it to last. If its Ecowood (tanE) your OK if its CCA they shouldn't be selling it to you.
IMHO I lay it groove up in playgrounds and public spaces and down in others, I usually ask the client what they prefer. I don't think it makes a difference to the longevity, infact I dont care if I lay 1 more sq.m of the ugly stuff again in my life. Go hardwood

[China]

The grooves are designed to face up, to help orevent the surface becoming slippery when wet, this thing about ventillation is purerly and simply a myth started by somone who did not know what they were talking about or was attempting to cover up the fact that they had fixed them upside down. The grooves are not deep enough to have any significant affect on releasing trapped water from the joints, if you are still udesided ask the manufactuer

[Jack E]

You can now get it grooved both sides.

It was originally designed for the grooves to go down to prevent rot.

So many idiots put it groove up because they thought it looked better.

Cheers, Jack

[Sir Stinkalot]

Ahh this old chestnut just never dies