Bill wrote:
SWMBO left heavy flower pots on each end of our 48" unsupported step
made out of Trex this summer, and the Trex boards warped (very
bad--more than 2").

The design looks poor, so that's where I'll point the blame. ; )

Here is a drawing of the current design along with my proposed
solution: http://web.newsguy.com/MySite/deckstep.jpg

Questions:
1. I would prefer to use screws (rather than nails) to add new
structural support, so I don't cause damage. 2.5", pre-drilled?

2. In the diagram of my proposed solution, I would have screws being
(not) held by end grain. I know that this is a problem.. What is a
smart, easy and inexpensive way to get around this here? It looks
like I need a brace/bracket of some sort. I would like my repair to last!
: )
3. One of the new 5.5" wide Trex boards will have to be "ripped" to
4.25". Is the stuff difficult to cut? Can I use a cheap 40 or 60
tooth blade (do I need to use a router)? The Trex website suggests a
40-tooth "carbide tipped" blade and/or router, I believe. I can
practice on the stuff I remove, but as soon as I remove any, I'm
going to create a "safety hazard". I haven't even bought the new
Trex yet, I'm just planning.
Here is a copy of the SU file, if anyone would care to use it.
http://web.newsguy.com/MySite/DeckSteps.skp

(Thanks)
Bill

Unless you simply don't want to see the fasteners in the face boards, there
is no reason you can't screw through them and into the end grain of the
supports you're going to put in. That would be a common approach to
something like this.

--

-Mike-