Our stair stringers were delivered and I set to work building the first run up to the landing. We’re using 14″ LSL stringers up to the landing because it has to span ten feet above the basement stairs. The stairs will be 42″ wide so there are three stringers, all notch cut. I considered doing an enclosed stringer, but I wanted the treads exposed on the side so we can have a wooden railing with iron balisters, plus the center stringer has to be notch cut anyway, so for consistency I notched all three. I also reinforced with a 2×4 glued and screwed to each one, per manufacturer recommendations.
Stringers installed
I used stair gauges on a carpenters square to mark the cuts. All of my cuts were exactly accurate the first time, the stringers fit in place precisely the way they were supposed to, and they were perfectly level and aligned with one another. The only reason it took me three weeks is because I was admiring how flawless it all was. Eh heh, heh, ugh. No. As I continue to discover, I am not a very good carpenter. I made systemic mistakes, had flaws in my original plan, and spent most of the last few weeks trimming and shimming until the stringers approached a semblance of what I originally had in mind.
Let me run down the, uh, opportunities for improvement I encountered. Firstly, my original model had a flaw that in retrospect to everything else wound up being fairly minor. I made several important measurements that accidentally included the thickness of the risers and treads. In the end I had to make some field adjustments. I also had to slope the back of one of the stringers because the landing is slightly crooked at one end. I almost managed to cut one of the stringers nearly two feet shorter than the others, but fortunately realized my mistake before I had caused catastrophic damage.
The more major issue I didn’t actually figure out until I had been scratching my head at the stringers for a week, trying to figure out why the backs of each step weren’t in line. It turned out I had made the same mistake I’ve now made on multiple other occasions, which is forgetting that the house is totally wonky. The opening to the basement stairs is bordered by a doubled floor joist on one end. I used that edge as the basis for building the landing, and the landing as the basis for the stairs. As it turns out, that floor joist is not quite perpendicular to the outside wall, something I should have realized after all my subfloor frustrations.
Shim shimmery
As a result, the landing is not square (like, at all). I have built yet another parallelogram. When I carefully and exactly laid out the stairs to the landing so that the stringers fit, they were skewed to one another. I wound up cutting two of the stringers a bit shorter to compensate, barely fitting them against the landing without sticking down (one may be protruding by a sixteenth, but it’s close enough).
Even after that correction I wound up going back and forth, trimming and shimming an eighth here and there until my levels and measurements started to coalesce around the goal. I’m pretty sure upwards of eighty percent of the edges have had some form of adjustment. As it stands I still have a couple of steps that need some tweaking before they’re acceptable. It’s been a bit of a slog, to the point that I’ve re-written this post multiple times over the last few weeks as the situation evolved. The good news is that I didn’t ruin my expensive engineered lumber, the stairs will be as close to perfect as I know how to make them, and hopefully I’ve learned enough lessons that the remaining stair framing will go more smoothly.