Client wants a rail down her three front steps. What stock do you usually use for construction? I was thinking 1” square tubing for the posts and 1 1/2”x3/16” for the rail.  The insides twists or branches and leaves.   Not sure on the clients wishes there.  Powder coated or rattle can?

Tubing has an anoint habit of having pin hole leaks in the welds that end up collecting water and then swelling and breaking.  Might as well go with bigger solid end posts and smaller solid pickets. 2 to 2-1/2” wouldn’t be to big for the top rail.  

Powder-coat is a good option but a high zink primmer and an industrial enamel is much easer to maintain. 

Because it's 3 steps*, it's technically an item that falls under building codes.  That specifies certain things like the size and grip nature of the handhold, the way the handrail portion must be terminated (this is a big one), and the side force the system must take.  And baluster spacing of course.  Top and bottom platform size also come into play and must be considered.

Start with the code...and then if you think you can fudge because no one is looking, you can do so at the client's peril.  People fudge all the time but I can't say whether it's appropriate in your case or not.  Places like the Bay Area or NYC, you darn well better be perfect...Indiana..? 

1" square might be a little light for the posts depending on a lot of other factors, especially how they are mounted to the steps.  Thin wall is probably too light so you are looking at minimum 1/8" wall in my opinion but since it has to play with all the other parts, that's nothing but a very rough guess.

 

* Code in most places is weird and kicks in a 3 steps where 2 steps isn't considered worth covering in most cases (but not all).   Codes is not uniform over the whole USA though so you do need to check local variations.   There is a VERY handy product that can be purchased online or even at your local home center called "code check" books.  They are more like spiral bound references and cover the basic codes that are most consistently needed...with drawings and examples.  There are code checks on plumbing, electrical, and general construction.  Not expensive, VERY good to have around, and makes a great Christmas gift 

1 minute ago, Charles R. Stevens said:

Tubing has an anoint habit of having pin hole leaks in the welds that end up collecting water and then swelling and breaking.  Might as well go with bigger solid end posts and smaller solid pickets. 2 to 2-1/2” wouldn’t be to big for the top rail.  

Powder-coat is a good option but a high zink primmer and an industrial enamel is much easer to maintain. 

Would you go with 1” Solis square or is that overkill for the posts?

Depends on the number of posts. Two undo posts and I would go with 1-1/4 or 1-1/2” one per tread 3/4-1” would be good. My self I think would go with the heavy end posts and then 1/2” pickets for decoration. 

But that depends on the architecture of the house. Mock up something crude in wood to get an idea of proportions that look good and work 

1 hour ago, Eric Schatz said:

Not sure on the clients wishes

This will figure prominently in the equation. I would look up some pictures on google to show her. I agree with Charles, for outside railing, I avoid tubing like the plague.

Sounds like you are doing a fabricated rail.