A rafter is a sloping beam in a roof truss assembly that supports the weight of other components, such as a ceiling or roof.
The rafter's sloped shape is what allows roofs to be supported over long spans. The vertical edge of a rafter is called the plumb cut. The bottom tip is referred to as the bottom wall plate height and the top tip is referred to as the top wall plate height. Each rafter has plumb cuts on both ends. Rafters usually terminate above a ceiling, at a ridge, or in some other way that allows them to support an upper structure such as a roof or ceiling. A horizontal structural beam supports the weight of any structure above it such as joists, studs and provides headroom under the structure it supports. A rafter can be made of wood, steel, or aluminium. The top tip is known as the roof peak. A tie beam often supports a rafter at the foot where no support from an upper storey occurs, or if there is no tie beam, then it rests directly on a wall plate. Roof trusses can be assembled using wood or metal depending on the use of the building. Most residential construction roof framing sections use wood rafters, whereas large-scale commercial projects use metal or related materials.
The truss assembly supports the roof structure of any building. The design of the house will determine the type of rafters that your building will have.
The principal rafter lies below the common rafter beneath the purlins. It is stronger than the commons rafter because it supports the entire roof deck. It connects directly to the king post, the tie-beams, and the struts. If roof loads are extreme, an auxiliary rafter can be added to support the principal rafter.
In a hip roofing design, the hip rafter runs from the ridge beam to the top plate of the hip roof section. Hip jack rafters connect the hip rafter to the top plate. A king rafter serves the same purpose in a hip rafter as the king post does in a principal rafter.
Buildings with a valley roof have a section that connects directly to the main building structure. This is the case for T or L-shaped houses. The valley rafter is found where the roofs meet.
This type runs from either the ridge board or hip rafters to the valley rafter.
A truss is a structural member composed of simple members such as straight beams and triangular shapes designed to support associated loads in tension and compression. The simplest form of a truss is known as a king post. In a building, a rafter is a sloping beam in the roof truss assembly that supports the weight of other components, such as a ceiling or roof. The vertical edge of a rafter is called the plumb cut.
A truss can be made up of wood, steel, or aluminium according to its application and local custom.
A truss often consists of beams at angles joined together to form triangles. The triangular structure of the framing members in a roof structure makes them very strong. Triangular designing of rafters is common in roofs and bridges where spans need to be longer than normal.
Roof trusses types include Howe (or common) truss, queen post truss, arch-braced (or bowstring), round (or wagon), tied-arch, steel I-beam, Warren (or box) truss.
The design or the truss assembly affects the attic space or how much storage you can use.A joist is a horizontal structural beam used to support flooring, while rafters are sloped beams supporting the roof structure.
The word "rafter" refers specifically to an individual triangular or rectangular truss in beamed and plasterwork ceilings, whereas "joists" refer to longitudinal beams of similar materials but without these features.
However, there are instances where both terms can be used in reference to residential architecture; for example, if one were building out the attic into individual rooms with their own roof space (either dormers or separate), then insulated walls would need to be supported by some means. These vertical supports would need to be attached.Rafters support the weight of other components, such as a ceiling or roof. Rafters usually terminate above a ceiling, at a ridge, or in some other way that allows them to support an upper structure. A horizontal structural beam with one end face upright (or nearly so) and one long edge (the lower edge when standing) on which it rests; it supports the weight of any structure above it, such as joists, studs, and provides headroom under the structure it supports. A rafter can be made of wood (lumber), steel, or aluminium according to its application. The top tip is known as the roof peak. A tie beam often supports a rafter at the foot where no support from an upper storey occurs, or if there is no tie beam, then it rests directly on a wall plate. The rafters for your house must meet your area's building codes. If the roofing needs of your project are complex, consult a structural engineer.
A girder (also called a bearer) is designed to spread loads onto other structural components such as girders, columns, piers, whereas beams carry vertically downwards only. Girders tend to be widely used in reinforced-concrete construction, while beams are most common in timber frame buildings. They are both similar in that they support an upper structure and transmit the load from one point to another. The primary difference between a beam and a girder is that beams rest on their own base, which can be top or top and bottom flanges, while girders often have multiple supports. A column does not need vertical supports because it carries its load by resting on the floor.
In traditional timber framing, three main types of rafter ties are used to resist their uplift forces: collars, trucks, and principal purlins. In addition to these, which transmit rafter forces directly to the collar beam, principal rafters may be supported on a mid-span horizontal tie. All of these elements help prevent excessive endwise movement under wind loads or seismic interferences.
Tropical hardwoods such as yellow bloodwood, tulipwood, and ironbark are great for construction rafters. These timbers have a nice tight grain that resists movement over time due to gravity loads, effects of high winds, temperature changes, moisture content of the air, or snow loads during winter. The best timber for ceiling framing is usually plantation grown softwoods such as rimu or pine, where strength and stiffness aren't required. Some of the most common timbers used for this purpose are yellow bloodwood, white beech, backwoods, ash, and spotted gum. The choice depends on your budget and availability in your local area. These all work well but will last longer if kiln-dried to 10% or less moisture content. This reduces the risk of warping over time due to changes in relative humidity levels.