I have a ~5 year old trex deck on the heavily-shaded North side of my house. I do get some black spots and staining as mentioned by so many other here. However I just recently started wondering how much the spacing of the planks causes this... the online install guide recommends 1/4". Mine were install nearly touching, maybe 1/16" at best.

Anyone have a sense for how much this contributes to mold, staining, etc? In "wintry mix" weather in the winter the water actually won't drain in a few areas and makes frozen puddles. Any of course it's a total trap for pine needles or anything else.

The options I see are:

1) do nothing, keep up with pressure washing 2-3 times/year

2) drill small 1/8 holes in various locations between boards to help drainage with little visual impact

3) Pull up and re-deck with the same planks (major effort!)

4) Use a circular saw to cut a kerf width between each plank lengthwise -- The plank edges are a full radious (aka half round) so I think the saw cut would be "down" in the seam a bit...

Thoughts?