Join Date: Oct 2007
Location: corvallis, Oregon
Doug fir is fine, especially cvg, for the handrail. You are already aware of the potential for splinters, so choose your pieces with that in mind. Sand well and watch for any lift up of grain. If you have any spots where that occurs, stop, inject some glue under it and secure it with wax paper and tape, or a block and clamp if it's larger. CVG has far less grain separation than flat sawn, so you'll likely be fine. As for finishes, yes, it will hold a finish such as polyurethane just fine. Same guidelines as any other wood, sanded and cleaned of dust. If you have a pitch pocket, then don't use that piece for handrail. End of that story.
As for making your own treads, no problem. You can joint and edge glue, or you can tongue and groove the slats. Just be sure your glue-ups are good. Using flooring for it? Well, you can, but it has its issues. Mainly, you have a series of grooves on the back side and any rip cuts made to fit the treads and risers to width will need to work around these grooves. Also, If you have an open side on your stairway, the edges of the flooring, complete with grooves, will be visible, unless you're attaching returns. But will you also then put returns on the risers? What about where the front edge of the tread rests on the top edge of the riser? Is there a groove there? In my opinion, using flooring for this type of tread and riser is more problem than it is worth.