Wall for floating staircase?

[flanagaj]

We are planning on having a floating staircase and the TA has not made any mention in the drawings to BC.  I assume it will require a SE to see what make up the wall which the treads will be mounted to, needs to be.  Just not sure whether a single skin 7N block wall would suffice or even a single skin brick wall.  I want the stairs cantilevered from the wall as opposed to having a single central spine below the treads.

Has anyone installed such a staircase and if so, how was the mounting wall constructed?

[crispy_wafer]

Nice idea, yeah I'd run it past your SE for peace of mind, or even @Gus Potter might lend an ear for his thoughts.  I cant help too much, because I've gone with central spine, however when time comes for manufacture, assuming you don't fabricate it yourself, don't be afraid to look up local fabrication firms and joiners for treads.

[Russell griffiths]

Whatever you think it needs over engineering Massively 

I witnessed a large  staircase that had a complex curve in it nearly twist off the wall as the temporary bracing was removed. 
 

there are some serious forces at play with cantilevers, and there would be nothing worse than a bouncy staircase. 
 

steel support structure buried in the wall for me, or a 140mm solid block wall. 

[markc]

A lot depends on the balustrade. If the handrail and infil (assuming glass) is designed as load bearing the cantilever is drastically reduced and a block wall would be ok. If the treads are true single cantilever’s then you are into reinforced wall territory. A bespoke stair company will have SE’s they work with regularly.

[Nickfromwales]

Defo 120x 50mm steel box section uprights into a 5” ‘stud’ wall, with same for header and footer, if you want longer treads and for it to be bombproof.

 

Glulam or 3” trimmer for head of stairs can be swapped out for a steel, if it isn’t already spec’d in steel for eg, to allow this to all be welded / mechanically connected so the best result of all.
 

We’ve had an excellent steel fabricator and welder on site this week sorting a knackered roof out, and the results are fantastic and quite cheap for what you get. Day rates for a welder vs chippy aren’t wildly far apart (max £100 a day difference) and they get a lot done quite quickly by getting stuff cut and made up off site, then it’s just install / clamp / weld / bingo bango. 
 

Steel is not super expensive, so worth finding out what it would cost to do this in metal afaic, and then know you never need to worry / revisit ever again.

Steel opens up an entire new world of possibilities, where’s other materials such as wood have huge limitations; a lot of wood finished stairs need metal spines anyways. 

 

[flanagaj]

Thanks all.  I am planning on working with a local steel fabricator for the steel aspects and will manufacture the treads myself.  Fortunately, I can manufacture the treads as I baulk at the £200 / tread that people on eBay are charging.  One option would be to have steel rods for the balustrade, which are threaded and connect each end of the treads to a steel beam in the ceiling. 

[Nickfromwales]

If anyone wants the details of a fantastic mobile fab / welder who travels nationwide, pm me.

 

Been a great few days with this chap and he’s proper old school (let’s get it done) with 35+ years on the stick. 

[Tony L]

6 hours ago, flanagaj said:

Has anyone installed such a staircase and if so, how was the mounting wall constructed?

 

No, but I'm planning this (that's if I have any money left when the build nears completion). I discussed my plan with my SE, & my drawings show standard 7N blocks laid flat - so my wall that the stairs will hang off is 215 thick (+ finish) rather than 100.

[Gus Potter]

17 hours ago, flanagaj said:

We are planning on having a floating staircase and the TA has not made any mention in the drawings to BC.  I assume it will require a SE to see what make up the wall which the treads will be mounted to, needs to be.  Just not sure whether a single skin 7N block wall would suffice or even a single skin brick wall.  I want the stairs cantilevered from the wall as opposed to having a single central spine below the treads.

Has anyone installed such a staircase and if so, how was the mounting wall constructed?

What a lovely proposal. This floats my boat as an SE.

 

I imagine you have seen a "floating" stair in say a tenement (Scotland) or a traditonal town house in Bath.  I'll try and explain how these roughly work. 

 

Each tread is not a cantllever. It is supported by what can be a thin wall at the inner edge.`

 

Simplisticaly the way we design these is to let the outer side of the tread rest on the one below and to make it work this has to continue all the way down.  The treads are actualy, in torsion so where they are built into the wall the wall has to be designed to resist the tread torsion,  so you need a good weight of wall above. By default the treads need to have torsional resistance. A traditional stone stair tread has enough beef to satisfy. 

 

You find more detail on the theory on the internet. 

 

It's not a design job for the faint hearted but most SEs can handle it.. but you'll need a good height of blockwork above (to provide ballast weight)  and maybe some engineering brick round about the tread end where they run into the wall to take the local torsional stress. 

 

 

 

 

[JohnMo]

So glad I built single storey - one or two levels of thought process deleted.

[Gus Potter]

On 16/08/2025 at 07:50, JohnMo said:

So glad I built single storey - one or two levels of thought process deleted.

It's remarkably simple once you understand where the loads go and how the the treads twist (torsion) on these "flying stairs". 

 

The secret is in the detailing of the stairs, the SE stuff is straight forward! Often the stair does not need to cost a lot more.. but the time is in the devil of the detail.. making sure that the surrounding structure is designed and built so the thing works. Most folk on BH split stuff up into packages, seek the lowest cost.. so it does not work logistically.. but then you can't afford your "flying staircase" as everyone else has cut off your options.. and you end up with some crap version that probably costs you more anyway. 

 

One way is lets say I go and buy a motor bike off the shelf. Then I shop about and but the parts of ebay  will cost me more. This is an affliction particular to self builders, but an unavoidable one. You need to know if you can afford to sefl build.. and if you have not done it before then your only way is to go the route of building a bike like by buying parts like a motor bike. This used to work ok as there was plenty money to be made in self building.. but now things are much tighter financially. 

 

Look at it this way.. these flying stairs have been built for hundreds of years.. do you think these old builders did this out of charity? For hundreds of years they know how they stay up.. in the last hundred years and a bit we have proved how they do their thing mathematically. The thing is look at how these old builders made their money! and then ask can I make the same savings!

 

If you have a look on the internet and search for flying stairs in torsion you'll see how they work. Technically you can do this with a good thickness of oak tread with some modification and with a good stringer bolted to the masonry wall it will work also. Lastly you can also utilize the ballusters and handrail.. it's a traditional way  but if you are enthusiastic then in the round it's massivley elegant as you use every part of the stair both architechturally and structurally.

 

And if you put all that together then you are on you way to having a work of art! It does not need to cost the earth!

 

 

 

 

 

 

 

 

[flanagaj]

On 15/08/2025 at 14:02, Tony L said:

 

No, but I'm planning this (that's if I have any money left when the build nears completion). I discussed my plan with my SE, & my drawings show standard 7N blocks laid flat - so my wall that the stairs will hang off is 215 thick (+ finish) rather than 100.

Can I ask whether your block wall was just single height or did you also have to carry it up through the second floor to provide some serious weight to the wall.  I’ve just engaged with an SE and she says she cannot help with the structural calcs for a floating staircase.

[Tony L]

I can’t say for sure, yet.

 

I had to ditch the Arch Tec whose drawings I already have, because they were so full of mistakes & he wasn’t good at correcting them, even though I was giving him plenty of help – so there’s no point in me telling you more about these drawings, because they didn’t reach the stage where I was ready to get the SE involved in the superstructure calcs (my foundations are already built).

 

I engaged a new Arch Tec & paid him (on 19 May) & I haven’t seen a single drawing from him yet, even though I was supposed to have a full set of draft drawings at the beginning of July.  Yes, I’m annoyed with him, but I’m still expecting his work to be good quality when I eventually see it.

 

When I get the new drawings, I’m envisaging my thick wall, with the blocks laid flat, will run up to the height of the first floor, then there’ll be upright blocks on top of this, flush with the wall beneath on the side with the stairs, & running all the way up to the vaulted ceiling/roof.

 

If the SE looks at the drawings & says we need to make a change, & go all the way up with the blocks laid flat, I don’t think this will create too much extra work for the Arch Tec.  I’d rather keep to upright blocks at first floor level, as blocks laid flat would eat up an extra 115mm of bedroom width, & cost more.

[flanagaj]

I am thinking of paying these for a design (Contact & Services - Home Design Tutorials Ltd).  I am struggling to find an SE who can do the calcs and their design service will be useful when sending out the quotes to local fabricators.  TBH there is no reason for a floating stair case to cost a lot of money.  It's a joke what some of these companies are charging.  Take for example, the oak treads.  They can be manufactured using a mitre lock bit and a router table and oak.  If you have access to a router table, saw bench and a planer thicknesser, you could save a fair chunk making them yourself.



 

[Gus Potter]

5 hours ago, flanagaj said:

Can I ask whether your block wall was just single height or did you also have to carry it up through the second floor to provide some serious weight to the wall.  I’ve just engaged with an SE and she says she cannot help with the structural calcs for a floating staircase.

That is a good honest response from you SE and I often wish for this where folk say "it's not my bag" . As an SE from time to time I'll say the same, I don't have the expertise to take on this. This is a condition of our SE registration.

 

To provide a bit of cost context to this, say you came to me and said would you, Gus design and sign off on a floating stair? 

 

I would first want to have a look at your drawings and see if there is a fighting chance of making something work. I would charge you £200.00 quid for that as there is no free lunch. If I think, yes I can make that work then the calculations are pretty straight forward if using natural stone,  but if concrete they are not as you then need to design and detail the rebar which is a lot of work as you have torsional effects. 

 

The main part of the work is in the drawing detail and making sure you as the Client don't cut corners and that the drawings specify the construction sequence. I have to do that as if you cock it up you will might want to take me to court!

 

My proposal is. If you want to pick my brains then you need to pay for that. I'll then walk you though and discuss how we might go about designing,constructing it in a buildable way . Then I will be able to give you a fee quote based on us working together. So long as you pay me a fair rate for a fair days pay then that is reasonable? 

 

 

 

 

 

 

 

[Gus Potter]

@flanagaj

 That was a bit of tough love but go for it if you can. 

 

Post more info and some drawing details and if I can help I will, for free! Others will chip also as there are folk on BH that know about this stuff, have construction experience "boots on the ground" but are reluctant to post in case they get a slagging. 

 

To be blunt you have access to a great resource on BH so you need to give a bit to get something in return. 

 

Your floating stair really interests me and I would love to help but I'm not going to do that unless you share enough info that other BH members can benefit from.

 

Just maybe you'll get some tips and you can go back to you SE and say.. I've read some stuff on BH and here is how you design it.. what do you think? 

 

Edited Tuesday at 22:21 by Gus Potter

[flanagaj]

@Gus Potter I have no issue with paying for your time and would not expect otherwise.  I am currently just trying to deduce whether taking the currently planned 4" ground floor block wall that is proposed and laying the blocks flat will suffice.  By doing that, I have already tripled the block bill for the wall.  If said wall then needs to run up through the fist floor as well, then that is going to add quite a bit of extra cost.

There is this company (Oak floating staircase treads including steelwork STAINED BLACK £3950 PLUS VAT | eBay UK) selling the kits.  Which for the treads and steelwork is actually not that bad.

But it's the structural aspect of the supporting wall that for me could be the deal breaker.  A cast concrete wall using forms and steel, could be done diy, but it's a big job and the risk of not getting formwork correct, will be an expensive mistake.  If for example, it was simply a case of laying blocks flat up to the first floor, then I know upfront what the additional costs will be.
 

[Mr Punter]

Can you ask the staircase firm what engineer to use?  It sounds like they do a fair few of these for developers so they must have worked out the simplest and most cost effective solutions.  Give them a bell.