The stairs on this plan show a big change in tread depth on the first curved stair tread. I know winders can have variable tread depths…can curved stair treads exceed 3/8″ variation in tread depth when compared with other treads in the same flight?
I wonder if all the treads on the lower flight should be curved so all the nosings are concentric and all tread depths uniform.
I also have considered an ellipse with a gentle curve in the middle of the stairs and a tighter curve on the flaired out side (right as you go down the stairs). The milder curve in the middle of the ellipse would result in the first curved stair to be less variable in depth, but with the more dramatic part of the curves appearing as the stairs spread out as they approach the bottom.
Also, are their some good web sources for working out stairs based on concentric ellipses?
Replies
The short answer is no.
All of the treads will have to be within 3/8". With the winder being measured at a point 12" from the narrowest side of the step, and have a minimum depth of 6"
The first curved stair on the plan is like a winder (narrow on the inside, wider on the outside), but I doubt that many inspectors would like it.I would hate to be in the position of building something from an approved plan and then still having to redo it.
I'm not sure if that would fly, either. I would go to inspections and see if it's a problem, or maybe not. Outside of the gates the trucks were unloadin',
The weather was hot, a-nearly 90 degrees.
The man standin' next to me, his head was exploding,
Well, I was prayin' the pieces wouldn't fall on me.
As long as it meets the code pertaining to winders I don't see that it would be a problem. It does look too wide in the picture. Definitely worth discussing it with the inspector before building it.
The fifth step up is the problem. The first four are curved but do not change in depth. The fifth step which is used as a transition is still shaped like a winder. And being that the code thankfully gives us a definite point to measure from (12" in from the narrowest point), I don't see where the problem is. It's not something that can be disputed. You can shape the step any way that you want as long as the prescribed rules are followed.
I'd say that the architect owes you two or more carefully scaled detailed drawings with an engineer's seal.
That's been my main complaint with architects, that they love to draw what they imagine but seldom care about making it real for the carpenter. I'd ask for materials specs too.
>architect owes you two or more carefully scaled detailed drawings with an engineer's seal.An engineer's seal for a stair riser detail? My engineer wouldn't look at stuff like that. The architect needs to supply carefully scaled detailed drawings for sure, and the risers need to be the same, but engineering on the treads and risers isn't part of that.
Kyle is right; the problem is not with the run of curved steps, but in the transition to the straight run.
At least as drawn, the first five risers have a common centerpoint in plan view (i.e. the risers must be concentric in order to maintain a constant tread depth). The problem lies between the fifth and sixth risers.
If you design the fifth tread to meet winder code specs, you'll be fine -- at least from a code perspective. Aesthetically speaking, I think these stairs will need the help of someone with a good eye for detail. Right now, the stairs have flare, but not flair. ;)
Ragnar
Just throw it back to the Architect. Explain to him that the stair run is uneven. On elliptical or curve drawings, he should the point where the radius point is. Maybe his new assistant drew this without his knowledge. The planchecker also missed it.