A stair carriage is framing underneath stairs which functions to add support to the entire structure.
How is a Stair Carriage Built?
A stair carriage is generally built using a heavy piece of timber. Using a right angle tool lines are drawn on the timber to form the shape of stairs. The top of the timber needs to be cut at an angle so it matches the framing for the second floor. This top cut will allow the stair carriage to rest flush up against the second story framing. A right angle is then cut at the bottom end of the timber to match the angle which will exist at the floor. This angle is based on the angle of rise the stair case will have.
The longer the stair case the smaller this angle will be. Then using a circular saw the timber is cut outside the lines. The stair carriage is then mounted to the floor and the framing of the second story. Following this the material being used for the actual steps of the stairs is attached to the stair carriage.