How are 2nd floor joists supported at exterior walls in old turn-of-the-century (1900) brick homes?
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They were typically set into beam pockets recessed into the masonry facade/structure. There would basically be a notch or hole left in the brickwork and the joist slid in. The vertical load of the joist is now supported by the masonry below in compression.
Brick veneer is what you commonly see today. Which isn’t structural. Veneer is one layer of brick
Solid masonry would be atleast a double brick wall, and where you would see this style. They build up so far and then have to lock in the rows of brick with sideways bricks to make the wall structural.
To get the floor to attach to it, they either use beam pockets in the masonry, or attach a ledger board to the masonry
Brick walls are multiple bricks thick. The thinnest walls are two bricks thick but they can be four or six bricks thick to support all the weight above them. When they get up to the height of a floor joist they lay the joist on top of the brick walls with room for only a single brick on the outside. They then lay brick all around this joist bridging over the top. So the joist is laying on the wall inside a small pocket. The single brick layer on the outside is protecting it from the elements. The brick wall above the joist may in fact be thinner then under the joist as there is less weight on it. The walls on the loft is therefore much thinner then the walls in the basement. In addition you often see the short walls are much thinner and may have a lot more doors and windows in them since they are not supporting any floor joists.
For lateral stability the floor joists are connected to the wall primarily through friction due to all the weight but also from a layer of mortar between the joist and the brick. If this is not seen as enough to keep the building upright then it might be considered to add metal bracing to better connect the joist to the wall. This may be inside the wall and installed when the joist is installed or it can be added on later on the outside. The lateral stability is important as the floor joists are what prevents the brick wall from just falling over.
Usually those walls are 3 layers of brick thick. The wood beams are set into the interior layer and bear directly on the brick.
The ends of the joists are cut at an angle called a firecut. This is so that the joist can rotate downward and fall out in case of a fire. Otherwise, the falling floor system might lever the brick above and cause the wall to fall outward.
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