Decking planks, grooves up or down

3

38thfoot

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Just about to relay part of my line on decking planks that will come into contact with the ground in places,

What is the consensus, do I lay them grooves up which possibly traps water or grooves down which exposes more surface area to dampness from below?
38
 
Grooves down, and a liberal dose of bitumin paint on the underside?
 
I have come across two or three types of decking. Some with wide spaced grooves and plain smooth back, others with similar grooving but with a very shallow narrow groove. As a previous poster mentions whatever side you lay on the earth make it well protected in whatever way you can.
As an aside I mention that I have used decking very successfully when building outdoor structures. The narrow ribbing version can easily simulate planking (siding for the Americans) and the wider grooved version is nice when used vertically. Whilst the completed building is not museum quality it can be made to look pretty good and of course will last years outdoors and not low around in high winds. It is also able to remain outdoors during winter.
 
Grooves up - I trust you are using 'full size' decking.ex 150 x 38mm
decking board.jpg
 
Either -you can't see the grooves once the roofing felt is added! :cool:
 
38thfoot said:
Just about to relay part of my line on decking planks that will come into contact with the ground in places,

What is the consensus, do I lay them grooves up which possibly traps water or grooves down which exposes more surface area to dampness from below?
38
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Will rot where in contact with Ground Guaranteed. Plastic Decking though more expensive is a better bet for such area's. As a rule I think that in the scheme of things cost wise the decking is relatively the least of the costs. Long term life and not having to redo a section is more important.
JonD
 
Any wood, treated or not will fair much better if allowed to dry on all sides. It's the constant moisture when in contact with the ground or covered with roofing felt that does the damage. That said, any wood will cup, check and warp when exposed to the sun. Linseed oil/turpentine mixture will help but must be applied once every year. Spar varnish is good also.

The problem with most of the applications we tend to use wood for is that the planks are in a flat position which allow water and the sun to really do their damage.

Many years ago, treated lumber became widely available. I saw it used extensively for roof top decks and other structures exposed to the sun. The misconception about pressure treated lumber is that it does not need protection from the elements. The roof top structures did not last very long and quickly dried to the point of literally falling apart.

By the same token I worked on projects where wood was used to build outside steps, decks, etc, many years before I got into the trades. All of these structures were painted and built from close grain, probably old growth, Douglas Fir.
 
The structure of timber means that the end grain is the most porous, and draws water along by capillary action. The side grain is less absorbent, so I'd say that covering the top and sides protects it from rainfall and water held in ballast, whilst leaving the underside open might mitigate against condensation. If you were to use something like air-dried oak it would last for decades, but using softwood, however it is protected, will mean replacing rotten sections on a regular basis, the only difference being the time between replacement. But I'm aware we all have our preferred methods!
 
Northsider said:
The structure of timber means that the end grain is the most porous, and draws water along by capillary action. The side grain is less absorbent, so I'd say that covering the top and sides protects it from rainfall and water held in ballast, whilst leaving the underside open might mitigate against condensation. If you were to use something like air-dried oak it would last for decades, but using softwood, however it is protected, will mean replacing rotten sections on a regular basis, the only difference being the time between replacement. But I'm aware we all have our preferred methods!
Click to expand...
Oh yes, but the decking's treated, pressure impregnated.

So, while I agree with you on the question of end grain, you just need to treat the cut ends.

But generally, you're better off allowing the timber to breathe.

Not always though - gate posts will last longer in clay soils than sandy soils, due to the lack of air in the soil.

Now for the rules of cricket..............................:devil:
 
and concrete will make them rot all the faster.
 
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