[quote user=“mid michigan steamer”]
I have been in this hobby since 1989 and have built 3 layouts; one in Ontario Canada, and two in Michigan…all in zone 5 or slightly colder, so I suspect my experience is close to your situation. We are in the midst of moving north to the Petoskey MI area and so plans are being formulated for layout #4 there.
I have tried to use landscape fabric for a number of purposes. The only thing it seems to be good for is stopping materials from mixing, such as between the bare ground and gravel, or along the backside of a retaining wall so fill doesn’t seep out through the joints. The woven or spun type fabric is best, the perforated plastic stuff will be a nightmare later on down the road when doing maintenence. Personally, I recommend not using it except for those two purposes listed. Weeds will break through it, and then you’ll have an even bigger mess trying to pull them and lifting the fabric with them.
As for your original question about plastic decking; I strongly recommend against it and the entire method of track on plank roadbed. My experience is that the plastic decking is really composite decking and includes a percentage of recycled wood fiber. It expands and shrinks significantly more than wood, is much heavier, is not as stiff as equal size lumber (hence the coments from others about it sagging or draping over the ground), is much more expensive than wood, and tends to absorb water when left in direct contact with the soil.
I used the track on plank approach on layouts #1 and 2 and learned not to use that style ever again in zone 5 or colder. Layout 1 actually faired better, I used cedar for that one. Layout #2 used pressure treated 5/4 decking. I learned the hard way that pressure treated that is available at most do it yourself box stores is not that great to start with, and is definintely not intended for direct ground coontact. It’s stands up well if use