Masonry Stair Walls and Connection to Primary Structure
Masonry Stair Walls and Connection to Primary Structure
(OP)
There are many reasons engineers are interested in connecting masonry stair walls to the primary structure. For shear wall applications a connection is needed to transfer forces out of the floor diaphragm and into the masonry. Sometimes it would be nice to brace masonry walls to the floor to reduce spans for out of plane bending. Unfortunately, every client seems to have a different interpretation for what connection are permitted to rated walls.
Some architects allow vertical slip connections as long as no gravity load is transferred into the wall.
Some architects insist on a completely independent stair structure. No connections of any kind at the floors; independent roof structure with joints in the roof deck.
Some architects do not allow connections at the floors, but will allow a shared roof structure.
Some architects will allow "break-away" connections that fail at low temperatures in the event of a fire. Epoxy anchors?
Has anyone else experienced these limitations? Does anyone have some code references that describe what connections are permitted to rated wall? I can never get a straight answer from our clients regarding attachment to rated walls.
Some architects allow vertical slip connections as long as no gravity load is transferred into the wall.
Some architects insist on a completely independent stair structure. No connections of any kind at the floors; independent roof structure with joints in the roof deck.
Some architects do not allow connections at the floors, but will allow a shared roof structure.
Some architects will allow "break-away" connections that fail at low temperatures in the event of a fire. Epoxy anchors?
Has anyone else experienced these limitations? Does anyone have some code references that describe what connections are permitted to rated wall? I can never get a straight answer from our clients regarding attachment to rated walls.






RE: Masonry Stair Walls and Connection to Primary Structure
RE: Masonry Stair Walls and Connection to Primary Structure
It's the engineer's responsibility to design the walls.
It's the engineer's responsibility to design the floors and roof.
It's the engineer's responsibility to design the connections.
It's the engineer's responsibility to design the anchors.
JAE was right, your architects are too pushy! I'm being comical but all the things you mentioned are things WE tell the architects. They give us the location of walls, floors, and roofs and we design them, connect them, and anchor them to make the building stand up. If the architect wants to make the structural decisions, he is more than willing to stamp the structural drawings!
On a more practical note, we have had a lot of success in design build projects (so the contractors like it) in basically framing around a stair tower with beams/girders and then attaching a long leg angle to act a pour stop on the top flange of the beam butted up against the masonry. We then anchor the vertical leg of the angle to the wall and set the deck on top of it. The guys in the field like it because it is easily adjustable and quick to install and the architects don't have an opinion about it.
PE, SE
Eastern United States
"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi
RE: Masonry Stair Walls and Connection to Primary Structure
This is exactly what I would like to do. Have you ever received any comments from the architect, fire marshall, or permit office regarding this connection detail?
RE: Masonry Stair Walls and Connection to Primary Structure
That sounds all very ridiculous. Stair shafts are used all the time for shearwalls with direct connections to the diaphragms.
RE: Masonry Stair Walls and Connection to Primary Structure
You can have the discussion with the architect too that either 1) you use the masonry walls you are already building to act as the LFRS, or 2) you build extra LRFS into the structure thereby increasing the construction costs. Seems like a straightforward decision to me.
PE, SE
Eastern United States
"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi
RE: Masonry Stair Walls and Connection to Primary Structure
The architect's argument has always been:
If a beam or floor structure with a posistive connection to the stairs fails during a fire event, the stairs could be damaged or destroyed during the collapse. Therefore, the connected elements would require a fire rating that meets or exceeds the rating of the stair enclosure. Fireproofing is sometimes ugly, costly, and generally something the architects like to avoid (especially spray fireproofing).
kylesito - since the angle is used as a pour stop, I assume that the anchors are encased in concrete. Are you concerned about the vertical deflection of the beam so close to a rigid wall? I think that the anchors will transfer gravity load to the wall as the beam begins to defelct.
RE: Masonry Stair Walls and Connection to Primary Structure
personnaly, I would have concern about seismic too. In Seismic Point of view, you don't want your block wall to take any force (vertical & lateral). The walls should be isolated from the rest of the structure to not add stiffess (that will change dynamic properties... stiffer building attrack more forces) nor resist seismic forces !
But i Know that the construction practice not always respect that because of fire safety...
It's a contracdiction between architecture and engineering requirements
RE: Masonry Stair Walls and Connection to Primary Structure
RE: Masonry Stair Walls and Connection to Primary Structure
I could see the argument about connections failing in a fire event. Although I am not a fire protection engineer in the least degree, my limited understanding tells me that it would have to be a serious fire event to reach the anchors which are encased in the floor slab. Nevertheless, we have never had a situation where anyone has questioned this detail.
I suppose it's an interesting point that you want to keep the stairs isolated for both egress and stiffness considerations. I must admit I don't know how to argue against that logic. All I can say though is that it's tough for us to justify the cost of moment frames when a perfectly good masonry that already needs to be built can do the same job. But, I think a lot of this is the flavor of the building industry in the area it's being built in.
McCalf...we have considered the deflection of the beam and camber the beam itself. We have not had a problem, however, in the installations we have done with this detail about overstressing the wall due to forces being transferred. If we ever had a beam long enough we were worried about it...we would probably provide vertical slots in areas of high deflection.
PE, SE
Eastern United States
"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi
RE: Masonry Stair Walls and Connection to Primary Structure
RE: Masonry Stair Walls and Connection to Primary Structure
RE: Masonry Stair Walls and Connection to Primary Structure
This is the problem in seismic design. We suppose that the wall don't participate or stiffen the building...and are not bearing
The architect and contractor build bearing walls !
RE: Masonry Stair Walls and Connection to Primary Structure
RE: Masonry Stair Walls and Connection to Primary Structure
"We shape our buildings, thereafter they shape us." -WSC
RE: Masonry Stair Walls and Connection to Primary Structure