Which material is best for building Grow-Boxes? And what about gravel in the aisles?

Q. I was telling my husband I needed 8″ Redwood or Cedar for the grow boxes and he asked if it wouldn’t be better to use “Trex” as that doesn’t seem to ever wear out.  Is there a reason to NOT use Trex?  (web site about Trex https://www.trex.com/)  Is there an advantage with Redwood/Cedar that is not there with Trex?

Also, we are getting dirt to put under the boxes and level the area.  They tell me it would be much less expensive to get crusher tailings (rather than topsoil).  Would this be just as fine since I’m putting grow boxes on top or should I get top soil since the roots may go down into the dirt?

A.  Redwood and cedar are good for Grow-Boxes because they last a long time, and do not deteriorate like pine.  However, they are expensive, and it costs much less to use pine and paint it, or even to use treated lumber.  Trex looks great, and will last indefinitely, but I suspect it is very expensive.  We encourage people to do things without incurring any more expense than necessary, so I probably wouldn’t recommend Trex for that reason.

 
Anything you put down on your soil will be there a LONG TIME.  Unless you want to deal with crusher tailings forever, I wouldn’t put them there.  Paying for topsoil isn’t necessary, however.  I would get any clean fill-dirt that’s available.  On the same subject, sometimes folks want to put gravel or wood chips in the aisles.  Unless you get a lot of rain and your aisles would be muddy most of the time, I recommend you leave them alone.  Just do the nominal amount of weeding it requires to keep them clean, and with no watering, they remain dry, clean, and pleasant.  Gravel, wood chips, etc., can be a real pain to push tillers, wheelbarrows, etc. through, and even walking isn’t as nice as on clean, hard, dry dirt.