Staircase Design

11 years ago

I ran into a couple oopsies in my design for the staircase (don't we all...? well those who do the stair design themselves :P)

Anyways, end of day the conclusion is I am cutting the width down. I originally wanted a luxurious 48" width, which quickly became 44" because I forgot about a future wall finish on the basement wall which will mean the landing + stairs move 4" out. To fix that, I just shaved 4" off the 48" width (since landing is as deep as the stairs are wide). After I thought I was okay, I then realized that the wall I have right next to my stairs is a plumbing wall (no problem) but that I can't double up two I-Joists (2.5" wide each, total of 5" width) NEXT to the stairs because those will block plumbing access to the basement soil and vent pipes. Consequently, my staircase must now be moved 5" over which cuts into my already small-ish living room.

Here's the math -
9' 9.5" Total Rise - (8' 9.5" to top of sill plate + I joist and floor finish)
13.5" Floor Thickness (includes I joist, sub floor, and roughly 3/4" finish floor)

Prefer 44" Wide stairs
Prefer no more than 7 1/4" Rise
Prefer no less than 10.5" tread (May or may not count any nosing)
I have 12' 6" from foundation wall to start of hallway (where stairs must start - perhaps not a good idea to start RIGHT at the hallway width, bumped back a bit would be better) - after subtracting 4" for future foundation wall finishes that leaves 12' 2". Then subtract the landing which would be 44" leaves 102" of length until the landing. After that, the stairs turn 90 degrees and go down the rest of the way. I would like to cut as few as floor joists as possible as a result of needing 6'8" headway at all times. So far it looks like I will need 2' 6" or so of additional floor cut out after the landing turn to allow proper headway.

I am weighing back and forth between less wide stairs, or maybe less tread - but it comes down to a point where I can only get 9 or maybe 10 stairs before the landing. According to an online calculator I need 11' 3" of open floor to have proper head room, but with a landing that messes the figure up and the landing becomes additional floor area opened up.

Is 44" wide staircase a decent size, perhaps too wide and could be cut back?

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Comments (3)

PRO
CASEY BUILDING SOLUTIONS
11 years ago
44" is very decent size.

Instead of 10.5" thread or 9.375" stick with 10" or 9" thread. Then select number of threads let's say 13. You need to compute from the height of the finished floor... If you don' like the rise increase number of threads: 14, 15 etc.
mushcreek
11 years ago
Using IRC code numbers, the minimum run is 10", and the maximum rise is 7-3/4". It's worth googling stair design, as even code compliant stairs can be somewhat uncomfortable to use. There are well-known formulas for balancing the rise and run. Getting an ergonomically correct rise and run would serve you better than making the stairs extra wide. Are these basement stairs? If so, they don't need to be so wide unless there is no other access to the basement, and you plan on carrying large objects up and down the stairs. Mine are 37" (36" is code minimum) and they are fine. I grew up in old houses were the stairs were very steep and narrow, so maybe it's just me.

I don't know what you're using to draw this, but I recommend the free version of Sketch-Up. That way, you can draw the stairs from all of the different views to make sure you get it right before you commit it to actual lumber. Make sure you include all of the building materials, and add a little for fudge factor. You'd hate to have a fussy inspector flunk you for being 1/8" out of code.
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Nicoletta
Original Author
11 years ago
It is a walkout basement so access with furniture is not a big deal. I do want the stairs to be open and feel fluid to connect upstairs from basement since the house is not large, the main living area will be in the basement so they will be used daily. I was thinking no less than 42" would be a good figure. I want no more than 7.5 rise because I know even that seems steep to most. I can stick with 10" treads and do .5" nosing which should be as close to the 7/11 as I can get.

My main concern is fitting the perfect number of stairs before the landing and turn so I don't have to cut as much additional flooring out for headroom. Sounds like I am on the right track with my numbers though.