Thread: Decking - what side is up?

Without exception the grooved side go's "DOWN!!!"

Decking is often seen grooved (reeded) side up, but the intention is reeded side down, the air spaces in the reeding help limit capilliary action drawing water into the joints where decking and joists meet, and provide some ventilation around the joint to minimise rot. Some people think the reeding is for a non slip upper surface but this is not the case. If installed reeding up, it is also much harder to clean as dirt etc is channelled to the base of the grooves and nothing is effective at getting it all out.

^^^
What he said..... spot on advice.

As pine is relatively soft, the reeded side also tends to get chewed up (stiletto heels, shoes with gravel, claws on large dogs) quite easily... and it's not something you can sand back to give it a spruce up. Using the painted side up (and applying more paint) will give you a better lifespan from the pine.

OK thanks folks.

Seems pretty conclusive.

Ji

I was told (so may be wrong) that the grooves were originally formed as a result of the machine that was used to produce the boards and were supposed to be placed down. However may people liked the look of the grooves so placed them up.

However it does make sense that placing the boards groove down should extend the life of the boards assuming that they will be exposed to the weather. If the are under cover then it really won't make much difference.

John

I think the intention of the grooves, indoors or out, is to reduce wobble of the boards, by having only two contact regions instead of continuous. Same reason applies to foot rings in bowls.

Cheers,
Joe

Malb is spot on.

Putting the grooves up, on the other hand, will not only increase the length of time moisture is trapped between the underside of the board and the joist, but retains water in the grooves, resulting in accelerated deterioration of the board.



Especially when combined with high-heels/stilettos. :wince:

The amount of decks I've seen that have been built by "builders" with the grooves up!

I'm a simple IT guy and I know the grooves face down to avoid moisture being trapped. My dad told me that, and it made sense when I was around 15.

Good Morning Li

China, Malb and all are absolutely correct when they say the readed side should be down to minimise capilliary action, and possibly rot.

But I put the readed side upwards on my deck because someone significant insisted that this looked much better. Harmony from decking !

Twenty three years later the decking needs replacing. The treated pine has thoroughly dried out and gone brittle - three boards have snapped so far. But there is no sign of rot anywhere; the CCA cocktail has done its job well.


Cheers

Graeme