Cantilevered stair vs masonry wall 5

[Jay_]

Hello all,

As the subject says, i am in one of those situations.

There is an existing solid masonry wall that need to support a one floor cantilevered staircase structure.

For the fixing of the cantilevered treads structure to the wall i am thinking of two options.

Option 1) using chemical anchors with anchoring adhesive but all these chemical anchor suppliers recommend one bolt per masonry cell and thats an issue since the anchor bolts spacings are going to be less than a masonry cell.

Option 2) using a sandwich connection between the treads beams and the other side of the masonry wall; basically welding steel rods on a plate, inserting it from the opposite side of the wall and fastening the structure on it from staircase side.

I think option 2 can be better than option 1, but i need guidance, advices, and even other options but taking into consideration that it’s an existing solid masonry wall and it is not under construction.



Detailing is a hobby,

 

[milkshakelake]

I'm working with architects all day, every day. It's a different story between having a wall you engineer yourself, with the express design purpose of having cantilevered stairs, and one that's already there.

 

[HouseBoy]

If it was easy..... they wouldn't need us!

 

[JAE]

Some kind of torsionally stiff system is needed inside the wall.

Yes totally agree. We've done a couple of them - free end cantilevered treads - both required either a large (hidden) steel tube in the wall or a solid cast concrete wall with embedded steel to allow for the cantilevers.

 

[HouseBoy]

JAE - Great pics

To answer the OP's question.... the "spread" of the bolts that you show in your sketch does not seem adequate to produce a load on the anchors that will (likely) be within the capacity of the anchorage.
Not sure how much "hiding" you can do but... I'm wondering if there will be a wall covering. Maybe that will allow you to bury something more substantial within the wall.
Also, the bending load on the wall is a big unknown (as suggested by the replies).

 

[Eng16080]

Do you folks ever work with architects? The suggestion of a stringer at the free end makes me think you don't!

This solution was actually suggested by the author of the thread a little ways up:

I am going to connect all the treads together at the free end.

I agree that the moment arm between the anchors seems minimal.