Constructing and operating an HO railroad outdoors is a challenge.  In Arizona, rain is not much of an issue but solar heat gain is.  Accommodations must be made during construction such as sealing the wood with an elastomeric paint. This paint flexes as the wood expands or contracts affording protection from the rain, when we have it.  But, and there is always a but, from mid-December 2009 through mid-March 2010, we had over 8 inches at my house.

Rain also means that scenery and ballast cannot be attached with the usual solution of white glue.  The substitution is a water proof glue called Titebond.  It is not cheap but generally it works.  Likewise, cheap miss-mixed interior grade paint from ACE or Home Depot won't hold up.  It must be exterior grade to withstand the sun and rain with minimal degradation.

Light rain is not so much of a problem even if it is prolonged. But the big drop, wind driven rain can dislodge ballast, bushes, and ground cover. I have begun applying a small layer of clear DAP Alex Plus (silicone infused) caulk and then pressing the ballast or ground cover into it before it cures. It works and has refused to budge even in the hardest of downpours in early March.

When using plaster cloth and Hydrocal, Plaster of Paris, etc. for scenery, you have to be mindful of the weather.  Rain on unpainted scenery elements is a disaster.  Each tree inserted into a completed mountain must be sealed to keep rain from entering and wetting the underlying plaster cloth.

It will eventually dry again, but in the interim it is soft and easily damaged.  In Phoenix as our humidity is typically single digit so mold does not appear to be an issue.

Even though I protect the track from direct sun, several pieces suffered damage.  The ties on the code 83 (from whomever, Atlas, ME, Shinohara, or Walthers) distorted rendering the section useless. What a pain to replace.

I made the mistake of installing curves with butt-joints. Wrong - an open invitation for a kink to develop if the caulk bedding is not perfectly applied. Soldering the joiners is of little benefit as the newer dual  purpose code 83/100 joiners feel as if they have a thinner cross section.  I view them as problematic.

So, I am replacing all major curves, and a good portion of the upper level track.  There were uneven spots where the dominoes met, etc.

Still using code 83 but with staggered joints.  The mainline curves are all 36-inch radius (outer) and 34-inch for the inner.

If any of this fails, I will abandon flex track and go to hand laying on wood ties.  I will convert the turn outs to Fast Tracks on either wood or PC board.  Even if it is one section at a time.