It's in the joists: A joist is a horizontal structural element that spans an open area and transfers loads to vertical members, generally floors and ceilings. If the joists run parallel to the wall, the wall is usually non-load bearing. However, if the joists are spaced from the wall at least 1-1/4 inches, then they are considered load-bearing walls. Load-bearing walls support any weight above them and transmit those forces to the ground or some other supporting structure.
Load-bearing walls are important in a building with more than one floor level because they transfer the weight of items such as furniture, pipes, and wiring between floors. Otherwise, each floor would have to be strong enough to bear all its own weight. Ceiling joists are always load-bearing; floor joists may be load-bearing or non-load-bearing.
The term "joist" is used for the beam that supports a second floor or roof. But a ceiling joist does not support a second floor or roof; it only transmits the load from the first floor to the foundation or another supportive structure. The term "joist" is also used for the wood slats that make up a platform bed. These pieces of wood are not meant to support anyone's weight, so they do not need to be load-bearing.
In general, if a wall runs parallel to the floor joists above, it is not a load-bearing wall. However, if the wall runs perpendicular (at a 90-degree angle) to the joists, it is likely to be load-bearing. The reason for this is that in order for a non-load-bearing wall to be safe, it must be able to support its own weight as well as any weight placed on it by people or objects. Since a perpendicular wall meets these requirements easily, it can bear any weight applied to it.
A lot will depend on what type of construction you are dealing with. If you are building a new house, then your builder should know whether your kitchen wall is going to be load-bearing or not. They would not want to build any room (especially a large one like a kitchen) without considering how it will affect the overall strength of the house.
If you are looking at existing buildings, then you will have to ask someone who knows about these types of things. A property owner or an architect might be able to tell you if a wall is load-bearing or not. He or she would be able to do this by looking at it visually and also by measuring it with standards such as the National Building Code. You could also call your local building department and find out for sure; they would be able to tell you which walls are loaded and which aren't.
However, in other circumstances, a bearing wall runs parallel to the joists. For example, if columnar support members such as pillars are used to support a ceiling, they will often be located close to the outer edge of the room. A wall built between these columns will be considered a bearing wall even though it does not reach the floor.
A load-bearing wall is one that transfers its own weight as well as that of any objects placed on it. In other words, it cannot be supported solely by the structure behind it. Load-bearing walls are crucial in buildings where no basement or lower level exists. They provide stability for other parts of the building and prevent them from being pulled down by their own weight.
Non-load-bearing walls are those that transfer their own weight but also rely on some kind of internal support system for additional stability. For example, a wall that uses drywall and wood studs as its main supports is considered non-load-bearing because it can easily collapse under its own weight. However, if steel beams were instead used as the main support system within the wall cavity, it would be considered a load-bearing wall.