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Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

(OP)
Early 1970's residential single-family house, Northwest GA, US.
Original Exit stairs from back porch failing (too steep, bad wood, bad handrail, etc.) and needs to be replaced.
Drop from top of old landing to concrete below = 105 inches.

Code requires a 80 inch head clearance, which can be met with the "usual" 30 degree (12 steps per 360) or 45 degree (8 steps per 360) only if very deep risers are chosen. And, in fact, this is what all commercial spiral stairs use. Winder stairs

Code for spiral stairs allows a very steep rise, and a reduced head clearance, but my wife's knees max out at about 7.5 inch riser height. She also wants an inside continuous handrail, and an outside continuous handrail. Since she can manage 7.50 risers, I can get my required 105 height with 14 riders, 13 steps, each at 7.5 inch, but each "wedge" has an "unusual" 25.71 degree. I believe I'll be "legal" since the 7.5 inch rise is greater than a straight stair, but less than maximum for a spiral stair.

But "classic" purchased spiral stairs use a tight radius, and everything is measured from the center of the vertical pipe. And she doesn't want that "tight" a spiral. So, apparently, I've got to "modify" a winder (circular stair) into code.

If my stage is a "normal" rectangle, I cannot get enough clearance for 80 inches headroom on step 11. The step itself is -82.50 inches (see sketch), but the headroom at the halfway point between Steps 10 and 11 is too low.

But, if I make the platform frame out of (for example) 3x3x1/4 welded angle iron angled at 102.86 degrees from the wall - NOT at 90 degrees from the wall - the platform will not overhang any part of Step 11 - only overhang Step 12. (Step 12 is at elevation -90.0 inches).

Thus, it appears that I will meet headroom requirements for a typical "winder" stairs, right?

Further, I can weld 3 of the platform framing angle iron legs "down" and the fourth platform frame (the one going out towards the vertical pipe) with the leg "up" - as if making a 3 inch toe board on that side. With a nominal 1 inch thick 5/4 platform board, this braces the platform, and avoids the 10 deep usual 2x10 "wood deck" framing methods while still bracing the center pipe of the spiral stairs.

Center member of the spiral stair would be a 3 inch dia pipe, anchored by a 3x300 lb slip on pipe flange on a 12 inch deep footing. Frost depth for the county here.

Other limits.

Code requires a minimum of 36 x 36 landing at the top, but the 36 inch door swing really means I need at least a 38 x 38 platform at top. This platform could be larger though.

Minimum clear opening between handrails for each "wedge" of each stair step is 26 inches, but I can weld up steps that are wider. Code requires at least 7 inches tread depth at a distance 12 inches from the inside (narrow end) of each wedge. That requirement can met with a 25 degree wedge angle - but only if the "inside edge" of each wedge is measured from below the handrail. So I'll have to weld the frames around each wedge to create a clearly visible "edge" to each step.

Code requires a 1.5 inch gap between the "wall" and the handrail, and allows either a 1-1/4 or 1-1/2 diameter "pipe" to used for handrails. (I plan on using a 1-1/4 dia pipe, 1.66 OD) If the center pipe is 3 inch pipe (3.500 OD), then I can pre-fab each wedge with a 3-1/2 nominal sleeve (which will be slid around the 3 inch vertical and then welded.)

Thus, from centerline out, I plan on using:
3 inch pipe = 3.500 OD
3-1/2 inch sleeve = 4.000 OD,
1.5 inch gap
1.66 inch dia handrail
26 inch clear space
1.66 inch dia handrail

Anything I've forgotten?

Or any basic errors in my assumptions about how I am reading the latest residential Code?

RE: Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

Not sure about code in your current area, so I can't comment on that - but from an ergonomics standpoint I want to ask about future usability.

-Her knees can handle a 7.5" riser today, but what about in 10 years?
-Is this the primary entrance and exit to the dwelling? In an emergency situation this could lead to problems.
-Ensure to provide some sort of rain barrier, or drainage scheme for the stair risers themselves. This isn't a cheep project, so you want it to last and pooling water & wood don't mix.

Also something seems to be wrong with the attached sketch, it opens in adobe for about a half second then greys out the whole drawing.

You might want to delete this from the hobby section and post it in the structural branch - a lot of very smart people over there who like to help.

RE: Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

(OP)
Understood.

No, this would be the fourth exit: Back porch out to backyard.
Front door from driveway. Two steps at 6 inch each.
Garage to kitchen door. One step at 7 inches.
Basement to back yard: No steps.

Image should be a jpg. Not sure why it would be graying out in Adobe.

Thought seriously about Structural Forum, but it's not exactly "business" since I'd be welding it up myself.

Treads would be either sawn 2x10 pressure-treated "wedges" or a commercial non-skid-topped open grating product. Not decided yet. 5/4 decking products are attractive, but at only 5-1/2 actual width, they're a bit too narrow to use as-is.

RE: Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

You may have room for a (patented, one source) LaPeyre Stair, which can be quite steep, and still straight in plan, and safe, and weird looking but not claustrophobic.
... and probably cheaper than the nonstandard everything you're proposing, if your labor is worth anything at all.

Mike Halloran
Pembroke Pines, FL, USA

RE: Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

Circular stairways are not considered approved exit stairs in non-residential settings. Be sure that you are in compliance with local code.

RE: Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

(OP)
Well, this is residential single-family, so that clause should be OK.

The backyard slopes strongly down from the house, so a straight per-Code 7x11 rise-to-run stair is not practical out of the back of the house.

RE: Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

Sam Maloof Tour

This mostly is furniture. I have seen copies of his rocking chairs with price tags of $7000. If you go down through the photos, you will see nifty spiral stairs.

--
JHG

RE: Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

I like those LaPeyre Stairs except for the price. Might be able to use the concept in a set of home made wood stairs to get into the attic of my garage.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Circular-Spiral-Winder Stair. Can This Arrangement Solve A Problem Fit?

Sorry to hear that, I thought it was a cool design option. I don't think they would be allowed in my area though (Canada), the way the code is worded the stair risers cannot alternate.

It might be worth it to find someone local to review the design before you submit for permits (sanity check if anything).

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