Decking - grooved side up or down?

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?:rolleyes:

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.:D

Thanks in advance

Donno

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

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 ;)

Definately down. Would I lie?:D :D :D

For the reason above, to stop the rot.

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

Mental Note!

Avoid any advice from those who told you grooves up.

But don't take my word for it.

They are desinged to go grooves down

BUT

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

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)

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

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.

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.

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

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

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

Ahh this old chestnut just never dies :)

Jarrah has only the good side grooved. The guy at Gunns (what used to be Bunnies) assured me that groove down was only invented by some wan*er on a tv show. However... it does make some sense to go groove down as per other posts or groove up, as per other posts. Ah this is just like the daylight saving arguement - perennial.

I reckon lay'em groove up then next one groove down... at least then yer only half way wrong!https://www.ubeaut.biz/crazy3.gif

GROOVES DOWN...the way it was always meant to be...also,a knock on the surface of the smooth face is less likely to damage/splinter as if it were laid the upside down.....but if anyone insists on their deck holding water and mould on the surface, splinters in their feet and a deck that is difficult to sweep dirt from, go the grooved look

just as importantly, the pine has excessive expansion and shrinkage, looks horrible and buckles terribly

One other major factor is cleaning. Much easier with grooves down with less trapping up dirt and dust.

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I have built acsess ramps that always have the groove up and running across the slope. I wouldn,t do them any other way.

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That's one situation where it might actually be a good idea.

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Most decks are treated pine and should be able to stand being damp.

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I wouldn't say that. Most decks I've seen around here are hardwood. There are T/P decks but most people consider them, cheap.

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If the smooth side was the face then the ripple side would be on the outside of the pack when they are delivered.

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I got a heap of Merbau decking earlier this year. Many of the boards are still showing the original rough sawn surface. Without exception, this is on the groove side.

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Jarrah has only the good side grooved.

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I've haven't bought jarrah decking but don't know why it would be any different to any other hardwood decking. See above.

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The guy at Gunns (what used to be Bunnies) assured me that groove down was only invented by some wan*er on a tv show.

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You actually believe what someone who works for Bunnings tells you?

As for non-slip, the grooves might help improve traction perpendicular to the grooves, but they are even more slippery parallel to the grooves because of the reduced surface area under your foot.

oh, why not just jump in. I was having a read of the public works specs for buildings, the modwood product and treated pine was mentioned and specified that in non weather protected areas that it is to be laid groove side up perpendicular to the usual direction of travel across the space.

As for manufacturers, CHH recomend reeded side down for air flow, but gunnersons say, reeded up for grip or down for look - your choice. So probably the only people who are wrong are those that categorically say that one way is right, given there's a debate amongst manufacturers, and I'm pretty comfident that the people who make the stuff know their product pretty well.

My best guess is that reeded side was introduced to try and minimise cupping, but the marketing dept decided that would be admitting a failure, so some have changed the message to helping dry out, and some for grip.


For those that are convinced as a certainty that its to stop rot, and should be laid face down - think about this for a second - cca is immune to fungal attack and will not rot without seriously improper installation. Further proof of the longevity of the product can be found in any boardwalk over wetlands where they use , guess what?

The answer is 42

Exactly

6 x 9 = 42

Well, there are really two questions that need to be answered:

1. Why was the practice introduced?
2. What is the best way to install it, the above notwithstanding?

It seems as though getting an answer to number 1 is going to be difficult. Everyone thinks they know why it was first done. I know why I think it was done but I don't have any way of proving it. However, it doesn't really matter very much, does it?

As for number 2, it probably depends on the situation. I will always put it groove side down because a) I don't like the look of the reeded side, b) it seems to me that this is the way it's meant to go, and c) it's harder to keep clean with the reeded side up.

I have lived in a house that had a grooves up deck and you have to sweep it with the grooves, which doesn't always work out to be the direction you want the dirt to go.

Finally, if you install it groove side up, some people are going to tell you it's upside down. If you install it groove side down, or use the non-reeded variety, no-one is ever going to notice.

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For those that are convinced as a certainty that its to stop rot, and should be laid face down - think about this for a second - cca is immune to fungal attack and will not rot without seriously improper installation. Further proof of the longevity of the product can be found in any boardwalk over wetlands where they use , guess what?

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They do it on hardwood decking too, not just treated pine. The rot argument suggests that the reeds help prevent the joists from rotting, not the decking.

I agree with SilentC. I lived in a rental place previously with the grooves side up. It's a bloody pain trying to sweep any leaves, flowers or dirt if the grooves are side up.:)

Why not use cement?

To keep the deckheads out.

Too many deckheads in China

Wow:D

there certainly are a few reasons for and against grooved side down or up. I have decided, and in fact have laid the decking groove side up. (Sorry to those advocating the opposite:( ). The deck is covered and is not likely to become damp at all so I really have no rotting problem. Yes I get leaves blown onto the deck and yes it is a pain in the @rse to sweep the leaves up as well as dog hair. However I tried a few strips of decking prior to screwing them into place and I liked the look of the grooves on the surface. I guess that is the best guide I would offer if anyone asks me the same question after reading all of your most welcome and highly respected responses.

Thanks for the information because it really assisted in ensuring any decision I made would not be too drastic.:)

Donno

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Thanks for the information because it really assisted in ensuring any decision I made would not be too drastic

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But you laid it all upside down. You can't get any more drastic than that :eek:

;)

Donno, yer'll still slip on them if they get wet and green... but ever since they introduced the grooving, I put them groove-side up. Never saw a deck smooth side up & grooves under but then.... Water blaster is good for dog hair et al.

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Never saw a deck smooth side up & grooves under

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Do you make a habit of crawling under people's decks to see if there are grooves on the bottom?

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Water blaster is good for dog hair et al.

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No drought over in NZ then? ;)

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Originally Posted by silentC

Do you make a habit of crawling under people's decks to see if there are grooves on the bottom?

No drought over in NZ then? ;)

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1) Sometimes, when full of XXXX, searching for spiders & snakes to play with. But anyway, all that fine hand-crafting... it shouldn't be turned face-down (errr... not sure this line of reasoning is going to survive):D

2) Got a water tank Mr C. Gets plenty dry in North Canterbury make no mistake. Bare earth and stones. Rocket (horse) begging hay from November to March some years. However, there is a cunning plan to damn up all the rivers (Hell with the fish) and convert the desert into dairy pasture. When the gas runs out and the pumps stop there will be plenty of steak... and dry grass.....:rolleyes: bare earth again as nature intended.

i may as well put my bit to the ongoing discussion.
IMHO the reeding has nothing to do with anything other than an asthetic choice.
The only no-no I would suggest is to run grooved decking on a ramp in the direction of the slope.
Reeded boards offer more grip when installed at right angles to the path of travel & much less than unreeded when installed in the travel direction.
I suppose the dilemma is when there is no defined or 'normal' travel path.

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Originally Posted by silentC

Finally, if you install it groove side up, some people are going to tell you it's upside down. If you install it groove side down, or use the non-reeded variety, no-one is ever going to notice.

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Best argument I've heard.

I put the grooves on the decking timber face up three years ago. Any issues in taking them up and relaying. Thought using slightly thicker twistlock nails in the original holes wouls be OK...
Over to you learned folk.

If you're happy with them the way they are then leave them. You may experience issues long term due to the fact they're designed to go grooves down for airflow blah blah...but honestly why bother taking them up if you're happy they way they are?

HH.

I agree, I wouldn't bother. You'll probably break half of it pulling it up.

But you'll know for next time :wink:

Grooves down because it is easier to clean.
As for "ventilation", give me a break! do you really think there is any gap left at all after you nail them down? Answer, no.
As for grooves up will make them rot quicker...no again. I've built a small decking path under a maulberry tree with no cover. During summer it is a black mess of rotten berries and bat's poo, and the only thing that washes it is the rain. 10 years later the decking boards are still structurally sound even when rather on the dark side..

Both of the houses I have renovated have had decks that have not been looked after properly (by former owners) and have needed sanding. Now, how would you sand a deck if the grooves are up??