A rafter is a sloping structural member that supports a roof. It runs from the ridge to the wall plate. It carries the roof load and transfers it to the walls. Rafters are spaced 16 or 24 inches apart. They are covered with sheathing, which supports the roofing material. A rafter is a beam, but it is called a rafter because of its position. It is the skeleton of the roof. It defines the shape of the roof and the pitch of the slope.

Rafters come in several types. A common rafter runs from the ridge to the wall plate. A hip rafter runs from the ridge to the corner of the building. A valley rafter runs from the ridge to the intersection of two roof planes. A jack rafter is a shorter rafter that connects to a hip or valley rafter. A collar tie connects opposing rafters to prevent spreading. A ridge beam supports the rafters at the top. Each has its own function. The roof is a system of rafters and beams working together.

Rafters must be sized for the span, the load, and the snow or wind. A rafter that is too small will sag. A rafter that is too far apart will not support the sheathing. The building code specifies the sizes and spacings. In cold climates, the rafter must be deep enough for insulation. In high-wind areas, the rafter must be anchored to the wall with hurricane ties. The rafter is a simple member. It carries the roof. It is a critical part of the structure. It is also one of the oldest. The rafter has been used for thousands of years. It still works.