Casting stairs up to wooden beams (indoors)

[Drikken]

Hello everyone.

We are in the process of building a new house with Ytong energy+ in both the outer and inner walls (365 mm and 115 mm respectively) and want to cast a staircase that turns 180 degrees to the left (with storage underneath) between the first floor where the floor is polished concrete slab and the second floor which will be a wooden joist construction. I wonder how you cast in concrete up to wood? None of the walls around the staircase are outer walls, and the builders have cast indoor staircases to beams or floors in concrete before, but never to wood.
Is it possible and if so, how do you do it, anyone have an answer?
We don't have construction drawings to follow, so I would be very grateful for thoughts, ideas, and solutions

 

[Snickarkirre]

Hello! Wow, what a project, not an easy task to shape a staircase like that. Impressive! Are you or the carpenters going to shape and cast it? That's a good question on how to solve that. Would it be possible to bolt something like a U-beam or a large angle iron to the wooden joist, welding some sturdy reinforcement bars to it? Thinking if you bolt one of the suggestions, the staircase would have an edge to rest on, while the concrete doesn't lie directly against the wood.

Is there a load-bearing wall directly under where the staircase ends? It's going to be an incredible weight for such a staircase, so it feels like simply bolting a beam/angle iron to the joist wouldn't be enough without additional support. Maybe it could have a steel column underneath or on the side? Or if there are walls on both sides of the staircase, maybe it could work to notch out the walls and reinforce and pour into the ytong so the walls help support the staircase?

 

[Drikken]

Hey! Wow, what a project, it's no joke to shape such a staircase. Cool! Is it you or the carpenters who will shape and cast it? That was a good question on how to solve that. Would it be possible to bolt a U-beam or a large angle iron to the wooden floor structure and weld on some sturdy rebar? Thinking if you bolt one of the suggestions, the staircase will have an edge to rest on while the concrete isn't directly against the wood.

Is there a load-bearing wall directly below where the staircase ends? It's going to be an incredible weight in such a staircase, so it feels like it's not enough just to bolt a beam/angle iron to the floor structure; it needs some kind of additional support. Maybe it's possible to have a steel column beneath or beside it? Or if there are walls on both sides of the staircase, perhaps it would work to notch out the walls and reinforce and cast in the ytong so the walls help support the staircase?

Yes, it's a big project, but also fun, I think, because not many have it, and I believe it will bring the right feel to the house's character with a cast staircase indoors. We plan to work together, the carpenters and I, so I will be there when it happens. I'm not quite sure about your angle iron idea, but the U-beam is what I have thought could work to let the staircase land on at the level with the upstairs floor.

No, we don't have any load-bearing interior walls, and where the staircase will come up, there will be a door leading into the small storage that should be underneath the staircase. Still, there will be ytong 115mm interior walls around the staircase, which I think can be reinforced directly into, or perhaps, as you said, notch a couple of cm and place weight there through rebar and casting, so the poor concrete slab doesn't bear all the weight alone. We haven't set the interior walls yet, so we can cast in rebar already when we erect them to get a good load distribution.

I'm also considering placing a steel column or something similar in the inner curve of the staircase to pull the rebar from the walls to, which should be enough for weight distribution when sharing the weight with the walls as well, right?

 

[Snickarkirre]

Yes, definitely a cool project! Feel free to post pictures when it's finished so we can see the creation. I'm thinking if you place the angle iron in the floor joist so the lower edge of the angle iron is the same as the lower edge of the stair, then the stair will have a ledge to rest on. Do you see what I mean?

Okay, if there's a wall all around, it's probably smart to use that to take some of the weight and secure the staircase. If you notch around 100x100 and 100 deep and then extend the reinforcement all the way out, you'll have a solid support for the stair's weight. If you just extend the reinforcement, I think it would cause a significant point load on the walls.

The idea of steel columns might be smart. It's probably good to distribute the weight as much as possible. I'm especially thinking so that the slab and wooden floor joists don't have to bear all the weight.