Half turn floating staircase

[SBMS]

We’ve got a half turn/switchback staircase. I’ve now just realised that we’ve got try and work out how to support the half landing. Timber or oak staircase so no modern steel thing that could be self supporting. 
 

Fairly stupidly I now realise, we had assumed that the half landing would be floating - as the staircase is in a corner. But there’s nothing to support it at the fourth corner (layout attached below). 
 

We could probably support the fourth corner marked with an X below via a post, or box the stairs in, but would really rather not. Is it possible to build some sort of a steel frame that cantilevers and supports the fourth corner so it floats? Can the half landing be supported by the staircase rising up to it (always read that staircases hang off the floor so need the floor to bear the weight of them, not other way round).  I’m no engineer and will probably ask our SE but wondered if anyone had come across anything similar?

 

 

Edited September 15 by SBMS

[nod]

Just run the Newell down to the floor 

[SBMS]

2 minutes ago, nod said:

Just run the Newell down to the floor 

Thanks @nod but that’s what we are trying to avoid

[Oz07]

Could possibly run string from above down into wall if having bespoke made then support landing off that

[joe90]

Initially I was thinking steel under stringer and welded to similar across landing to the wall, however what about joining the stringer to a similar section at an angle holding up the landing (difficult to explain) I will draw a diagram in the morning if you want).

[SBMS]

12 minutes ago, joe90 said:

Initially I was thinking steel under stringer and welded to similar across landing to the wall, however what about joining the stringer to a similar section at an angle holding up the landing (difficult to explain) I will draw a diagram in the morning if you want).

Thanks @joe90 that’d be great. It sounds like there’s options. I can ask our SE and was going to go to Stairbox but maybe a bespoke set are needed 

[BadgerBodger]

Interesting problem. A lot will likely depend up the wall itself. A 100mm block wall will unlikely withstand an eccentrically applied load but this is entirely dependent on span and all sorts of other factors.

 

I think a “floating” structure using steel stringer spanning the half landing to the upper floor will be most efficient. This solution would result in minimal deflection and the wall loads would be imposed as planned. 
 

An engineer will tell you quickly enough the section size, weld detail and end plate/locating detail i.e pocketed or plated and bolted. 

A timber leg as indicated by your X or centrally in between the flights with a timber famed landing bolted to the walls (it will likely be a significant section size) would also work. It would be worth running the proposal by your engineer either way. 
 

Edited September 16 by BadgerBodger

[Bonner]

7 hours ago, SBMS said:

I can ask our SE and was going to go to Stairbox but maybe a bespoke set are needed

They are all made bespoke anyway. An extended stringer should be relatively low cost and neat solution if you don’t want the newel post down to the floor. Still need the SE to confirm and then specify exactly what you want to the manufacturer (others are available if they won’t do it).

[joe90]

I too used stair box and found them very helpful, I had a half landing (not floating) which I built myself and stair box  supplied matching oak for it. My idea is as below, can’t see why it won’t work and stairbox might even supply without costing you an SE. I think it’s important how the join is made which is the technical bit.

 

CAD = crayon assisted drawing 

 

 

[ProDave]

I suspect the only way is a steel structure hidden behind the stringers to give the strength.  To me is seems a lot of extra work to avoid one newel post going down to the ground at that corner.

[joe90]

Well they join glulam beams with a hidden steel plate so don’t see why that can’t be done on stringers 🤷‍♂️ Stairbox will answer that I am sure.

[SBMS]

Thanks everyone 

[joe90]

36 minutes ago, ProDave said:

To me is seems a lot of extra work to avoid one newel post going down to the ground at that corner.

I have to admit i would rather not have a post to the ground, without it it’s really floating

[ProDave]

Can you clarify is the floating corner the bottom string going down to the ground, or the upper string going upstairs?

 

If the downstairs one as the drawing suggests to me, then the dod leg stringer joint will be in compression so the hidden fixing might be less difficult, but that will rely on the bottom of the stringer being properly fixed to the floor so it can't move and spread outwards.

 

 

[joe90]

29 minutes ago, ProDave said:

Can you clarify is the floating corner the bottom string going down to the ground, or the upper string going upstairs?

 

If the downstairs one as the drawing suggests to me, then the dod leg stringer joint will be in compression so the hidden fixing might be less difficult, but that will rely on the bottom of the stringer being properly fixed to the floor so it can't move and spread outwards.

 

 

Ah yes, I presumed it was like @nod picture but the arrow suggests it’s the opposite, well spotted Dave. Yes a compression dog leg joint will be less complicated 👍

Edited September 16 by joe90

[SBMS]

8 hours ago, ProDave said:

Can you clarify is the floating corner the bottom string going down to the ground, or the upper string going upstairs?

 

If the downstairs one as the drawing suggests to me, then the dod leg stringer joint will be in compression so the hidden fixing might be less difficult, but that will rely on the bottom of the stringer being properly fixed to the floor so it can't move and spread outwards.

 

 

It’s the downstairs one - circled in red on the attached with walls shown:

 

 

[joe90]

Great so ask stairbox to design as I suggested with a dog leg stringer along that side with the red circle to support that side of the half landing 👍

Edited September 16 by joe90

[MPH243]

Stairbox supplies there quarter landing stairs with a dogleg cut from single piece so should be able to do what you want.

 

You can just about see next to the carpet. 

[MPH243]

I just realised the oak was joined, the pine stairs to the basement is 1 piece I can see the oak plugs in the stringer.