Alternating Tread Space Stairs Joinery Question

[rmhinden]

I am working on designing and building an Alternating Tread Space Saving Stair for my daughter's new house.  The current design looks like this:

[attachimg=1]

The stair treads will be either 1" or 1 1/2" thick.  My question is how to join the stair treads to the risers (2" x 12").  I have been thinking of either dominos (10mm or 12mm) or mortices (w/ screws).

Any thoughts on this?    Pro and cons of each approach?

Bob

 

[Lincoln]

Must be housed in.

 

[rmhinden]

Must be housed in.

Please explain.

 

[derekcohen]

Dado and dominoed, or dado plus mortice-and-tenon.

Regards from Perth

Derek

 

[tjbnwi]

Let in/housed is placing the treads into a dado in the stringers. Below is pictured stringers for a library ladder. There are screws thru the sides hold the treads in place.

In your case you’ll need to do stopped dados to make it look right.

[attachimg=1]

Tom

 

[Lincoln]

Must be housed in.

Please explain.

Treads need to be housed into the stringers. Dominos will not be enough, need the strength of a housing joint.

 

[Mini Me]

I can't even begin to think how any Domino(s) could be considered strong enough on stair treads. One person of considerable weight missing a stair tread and landing on a lower one with all their weight on one foot would be a very high load to support, would it pass a building inspection in the US?

 

[tsercitpo]

He uses a CNC to make most of the cuts, but could still be a useful reference:

 

[kevinculle]

...missing a stair tread and landing on a lower one with all their weight on one foot...

If you miss a tread on that stairway/ladder you will be catching one two down during a rapid descent evolving into a crash.  This Geezer will stick to a more conventional stair!

 

[woodferret]

I guess an illustrative reason why everyone is calling for housed step is that I have a grandfathered basement stair that's steep and about the same size.  The steps were just side-nailed.  The nail is fine and hefty, but the treads blew out above the nail.  A domino will do slightly better, but it's still only 24mm-ish wide.  If you're concerned with taking too much material out of the stringer, then there's also the option of bottom support cleats.  The face/face nailing/glue is less susceptible to splitting failure than the end grain.

 

[Vtshopdog]

Side note not related to construction method:

My in laws have a set of this type of stair at their cabin.  Stairs lead to a heavily used loft type living space complete with kitchen.  I would say at best the steps are awkward to climb and pretty much scary to descend.  (that's coming from someone who lives and plays in the mountains and is totally comfortable traversing ridge top cliffs and crags).  I consider them to be halfway between a ladder and regular steps and there have been multiple discussions about how to replace them with something more conventional.  Carrying bulky or heavy objects down them is sketchy.

YMMV, but having been around this type of stair for 25 years, suggest you consider what purpose and how frequently the steps will be used. Could be ideal for space saving access to a seldom used loft or regrettable choice for a daily living area.

 

[rmhinden]

Many thanks for all of the feedback, very helpful.    The pictures from [member=4105]tjbnwi[/member] are really nice.

I will plan on housed treads into the stringers, and securing them with screws.  I may need to get a bigger router, not sure my OF1010 will be up to this

Regarding why this is being done.  This will replace a too small spiral staircase to the second floor.  There isn't room for a conventional staircase, and there are beams in the way that would have to be cut (and posts added) to accommodate that.

I am planning to adding a handrail to one side (and at the top around the opening) to make it safer to use. 

Bob

 

[Crazyraceguy]

For an "occasional use" situation, it might be ok, especially since it is replacing a spiral staircase. They have limited usability in the first place.
Definitely go with the housing method. They don't have to be extremely deep. It's just the fact that they are in there and pulled against the shoulder adds a lot of strength.

 

[luvmytoolz]

Many thanks for all of the feedback, very helpful.    The pictures from [member=4105]tjbnwi[/member] are really nice.

I will plan on housed treads into the stringers, and securing them with screws.  I may need to get a bigger router, not sure my OF1010 will be up to this

Regarding why this is being done.  This will replace a too small spiral staircase to the second floor.  There isn't room for a conventional staircase, and there are beams in the way that would have to be cut (and posts added) to accommodate that.

I am planning to adding a handrail to one side (and at the top around the opening) to make it safer to use. 

Bob

I'd just make a quick MDF template and use a trimmer with a guide bush to cut the dado. It'll do it just fine.

 

[rmhinden]

I'd just make a quick MDF template and use a trimmer with a guide bush to cut the dado. It'll do it just fine.

Thanks, will do.  I have one of the new Woodpeck 8mm shank bits with a top guide bearing, should do fine.

Bob

 

[Packard]

The first time I ever saw one of these staircases was in one of those “tiny houses” (400 square feet or less).  I thought that the only reason for these was a lack of space.

That type of staircase requires familiarity.  So for a bunk bed that one person uses, it is probably fine.

If it is in a communal area, where visitors might have to use it, it does represent a risk.  The risk being you have to know (and remember) to lead with the correct foot when descending.  An error on that matter would result in the risk of a substantial fall.

How space-starved is this new house going to be?

The average new house size is about 2,600 square feet.  You rarely see one under 1,400 square feet.  If it is for access to the attic, I could see this (possibly).  But I would still think it is a risk. 

There is less lumber in the final product, but the same amount of lumber is require to build the alternating step as a conventional step stair case.

I’m not a fan.  So take this information as from someone who is not-a-fan.

 

[rmhinden]

[member=74278]Packard[/member]

It's a floating home, about 900 sq feet.  New to my daughter, built in 1967.  Two levels, downstairs is living/dinning room, kitchen, and half bath.  Upstairs is bedroom and full bath.  I think it's pretty cute and a good fit for my daughter. 

Attached are a picture from the outside and the circular staircase that we are planning to replace.  I hope this provides more context.

Bob

[attachimg=1][attachimg=2]

 

[Packard]

That is very cool.  I walked one of those houses back in the early 1970s.  They were an item on Long Island (New York), because the skirted the property taxes.  But they disappeared after new laws were passed to tax the floating houses as though they were conventional homes.

For a short while I fantasized about living on one.

But my original point is still valid I think.

I’m right handed, right eyed, right legged and right elbowed.  I’m right eared and right hipped.  But I invariably use my left foot for the first step up or down a staircase.

I could imagine missing th first step up with little consequence, but missing that first step down sounds fraught with risk.

The split stains look neat, but I don’t see a real advantage and I do see a real risk.

The floating house seems like a winner though. I approve.

 

[cider]

When I toured Maloof's estate a couple years ago, they wouldn't let people on the spiral staircase that he had built.  I'm sure that's mostly because of preservation concerns, but they also implied that it wasn't the sturdiest thing in the world.  Made me feel a little better about my own efforts  [big grin]

 

[rmhinden]

It is done and installed.  Came out well, and fits the space.  Importantly, my daughter is happy with it.

The steps are morticed in and screwed.  Next step is to add some hand rails and a banister at the top.

[attachimg=1][attachimg=2][attachimg=3]