Do alternating tread stairs meet building code requirements?

[AdironDoc]

Placing the stairs in an open design cabin is proving a daunting task. Traditional stairs break up the room, obstructing both views and  traffic no matter where I place them. While looking at 6ft diameter spiral stairs, I noticed many examples of space saving alternating tread staircases. Unlike the wood spirals which don't appear to be DIY, the AT staircases seem straightforward and easy. I've never tried anything like them.

Does anyone have a feel for how they are in use? Do they comply with most  building codes? I'd be using them to get up to the balcony of a 400sf loft.

Doc.

[MountainDon]

As far as I can tell the code makes no mention of alternating tread stairs. The code focus is on maximum and minimum tread depths, riser heights, width, overhead clearance, handrails, and other details. Spiral stairs have their own rules. It's all in IRC Section R311.5 which can be viewed online HERE.

  There is always the possibility of asking and getting an exceptional starircase approved.  Lots of inventive staircases HERE. If they are in the USA makes you wonder how they were approved. I've noted in other places that some are in other countries.

[Erin]

Alternating treads, aka the Jefferson stairs, are usually not code-compliant, unfortunately.  However, it'll depend upon which code your jurisdiction has adopted and if they've made exceptions.  (For example, to reach a small loft)
You really need to contact your local code enforcement body on this one...

So far as the stairs, here's their page at Country Plans.  (I'm guessing you've seen the ones that are "closed-in" where these are open treads, but it's the same principle)

http://www.countryplans.com/alt_stair/

[Don_P]

there was a thread on the old ICC BB that went to 21 pages IIRC on stairs to attics, got a little toasty at times. This should give some idea on the variability of interpretation. My interpretation, which means exactly nothing, is that stairs that access a defined "habitable space" must comply with the code. Those that access another space do not need to comply. Notice that a pull down attic stair is non-compliant. The other common interpretation is that if you build it, it must comply.

My Dad was a building official after he went over to the dark side and got a job with bennies. Their next house had a ships ladder (another name for them) that went up to a storage space. Some people like them, I do not care for them (and that's being pc  )

Habitable space; A space in a building for living, sleeping eating or cooking. Bathrooms, toilet rooms, closets, halls, storage or utility spaces and similar areas are not considered habitable spaces.

A space on a set of plans is what it is labelled not what it might be.

Do consider one thing when building stairs or labelling rooms though. There may be a dark night when 2 linebacker sized guys in full gear need to carry a loved one down those stairs in a very big hurry.

[MountainDon]

Do consider one thing when building stairs or labelling rooms though. There may be a dark night when 2 linebacker sized guys in full gear need to carry a loved one down those stairs in a very big hurry.

Thanks Don_P    That (and similar items) is something to remember when thinking of short circuiting codes at anytime. Think of the what if's.

[AdironDoc]

Good things to consider. Considering my place will be 20x40, not small, not large, I'll try to stay compliant. I don't want my kids, or for that matter, their grandparents, falling down a flight of stairs when they missed a step. If I go with an open look, like 2 logs as stringers with half log steps, I could turn the stairs into a welcome part of the decor. 7-3/4" rise, I believe is the maximumper step. At 8ft for my ceiling, I suspect I'd need 9ft of total rise to the 2nd floor. That should be somewhere on the order of 11ft? My cabin is 20ft deep, so the stairs will cut across the center hall.

[glenn kangiser]

Doc, I'm guessing you are going straight run for the center area of the loft? 

You could start along a wall then do a 90 degree turn on a landing toward the center of the loft keeping 6'8 headroom minimum.  I didn't work it out but it may keep you out of your hallway.

[AdironDoc]

That's a definite possibility. I'm sitting with graph paper and a ruler and looking at all the options. Fortunately, although I'm limited to 20ft depth, the ceiling height downstairs is 8ft but the walls are 12ft. The outside walls upstairs end up having a 3ft6in starting height so no problems with hitting the roof slope. Of course a free floating straight staircase will be a two rail setup. Minimum width requirements are 27inches. Rail to wall, 31.5in, and wall to wall 36.

Nice to have possibilities. But choosing is never easy.. Thanks

[Don_P]

Remember the 4" maximum gap rule with open treads. That requires a tread thickness of 3" to 4" depending on final rise.

This was as tight as I could draw a winder in a small house this summer, still need to get over there before they get back in spring and build them.


You mentioned spiral stairs being out of reach for DIY. You also mentioned welding. I think this would work; A steel post from floor to ceiling, the next size pipe that slips over this pipe is purchased just as long but is cut into pieces the heighth of the rise. a bracket is welded off of this that a wooden tread is screwed to. Stack them up on the post free to turn individually. Install the post, twist the steps into alignment and tack weld the post back together. We worked on a factory one similar a few years ago.

[AdironDoc]

Nice set of stairs, Don. It's got a smaller footprint than I thought. I could end up with a L-shaped staircase with the same orientation if I hug the wall.

I'm a beginner welder and would be reluctant to spot weld anything as important as stairs but I did see a DIY spiral staircase kit online. The set used the center post with spacers like you mentioned, but the overall look was very industrial. I'm leaning towards using two straight timbers, hand peeled with half log treads. I'll craft railings and spindles with the tenon cutter. I'm shooting for a rise of 7 3/4" and tread depth of 9". I'm not sure what the space will be between the risers since they are half logs and semicircular.

Something like this. Just can't figure out what to do with the space below.