Decking, pressure treated wood, should I treat it?

[compact]

Hi

Nearly finished the decking, however couple of questions.
We are happy with the style and finish at the moment, so would be happy to stop, however I am a bit concerned about wood and weather.

1) Fence post ends, should i put a horizontal plank on the fence to help close the wood, as the fence post has open grain?

2) Should I treat pressure treated wood? If so what and when.

Basically how good is pressure treated wood

Thanks

 

[big-all]

untreated timber will loose the green tint and go the colour off untreated fence panels
tops off posts are seldom a problem at ground level where the moisture level can be maintained around 19% for a long time will cause rot
you can slope the top off the post or use post caps iff you like

 

[JohnD]

I'd certainly go for post caps, and watch them for splitting or coming off. Good idea to drill the caps before nailing or screwing down, they are inclined to split.

Even with slanting, rainwater will penetrate the end grain of post tops and accelerate rotting. The treatment does not penetrate far. Once the grain has opened and decay begins, water will penetrate even more easily. I would personally give the whole thing a few coats of decking stain or oil as well, it leaves a water repellent film that reduces water absorption for a few years.

If the ends have been cut, give them several flowing coats of a spirit based timber preserver such as Cuprinol and let it dry before staining.

If you have any upward-facing knots in any timbers, drench them in preserver because rainwater will get in to the heart.