Roof rafter spacing, span and sizes | Rafter spacing | Rafter sizes | Rafter span | how far apart are roof rafters.
In general, for a 20 to 22 foot span, the rafter size need to be 2×12 lumber, while for a 16 to 18 foot span, the rafter size have to be 2×10 lumber. Likewise, for a 14 to 16 foot span, the rafter size ought to be 2×8 lumber, while for a 10 to 12 foot span, the rafter size got to be 2×6 lumber. In addition, for a 6 to 8 foot span, the rafter size need to be 2×4 lumber.
The spacing, span, and sizes of roof rafters depend on various factors including the type of roof, local building codes, and the load the roof needs to support. Here are some general guidelines:
Spacing: common rafter spacing is 16 or 24 inches on center (OC), but it can vary based on local building codes and the type of roof material.
Span: the span of roof rafters is determined by the distance between load-bearing walls or supports. The longer the span, the larger the rafter size needed to support the load. Roof pitch (slope) also affects span. Steeper pitches can have shorter spans.
Sizes: rafter size is determined by factors such as span, roof load, and species of lumber. Common rafter sizes are 2×4, 2×6, 2×8, and so on. Engineered lumber or trusses may also be used for larger spans.
A rafter is a structural component build of wood or steel that is used as part of a roof construction. Rafter runs from the ridge or hip of the roof to the wall plate of the external wall. Rafters are generally provide in series, side by side, providing a plateform to support roof decks and roof coverings.
In many countries such as in US, Canada United Kingdom roof rafter made of wood/ timber are much common to build a house. Many species of wood are used to provide timber which have much strength.
Rafters are usually made of pine or cedar tree, for longer span rafters, building materials several manufacturers have created Laminated veneer lumber (LVL) rafters that can be 2–5 times longer than typical wood rafter. In US, most wood rafters have maximum length of 20 feet.
The area which has heavy rainfall and snowfall require good drainage for roof, roof drainage depending on slope of the roof provided, based on slope of roof it is categorised into two types flat roof and pitched roof or sloping roof.
The spacing of roof rafter is just one of the component used to determine the minimum size of roof rafter. There is no any standard rafter spacing measurements. But generally rafter spaced typically either 12, 16 or 24 inches apart in one of several industry -standard increments.
What Is Rafter Spacing
Rafter spacing is the distance between parallel rafters or roof joists. It is measured from the center of one rafter to the center of the next, also known as ‘on-center’, which makes it easier to determine the number of rafters based on the building’s length.
The typical on-center spacing, according to the International Residential Building Code (IRC), is 12”, 16”, 19.2”, and 24”, which means the actual space between the rafters is 10.5”, 14.5”, 17.7”, and 22.5”.
Standard industry roof rafter spacing in inches are 12”, 16”, 19.2”, and 24” on-center, which means the actual space between the rafters is 10.5”, 14.5”, 17.7”, and 22.5”. Depending on all contributing factors though, 16” and 24” are commonly used for most buildings. The wider the space between rafters often results in rafters of greater depth too.
Rafter spacing in mm for different sizes are kept at 300mm, 400mm and 600mm apart. Standard spacing between rafter is 400 mm centre to center. The rafter which are kept at lower spacing can allow longer distance to span as compared to joist spaced further apart.
How far apart are roof rafters
Standard industry roof rafters spacing are 12”, 16”, 19.2”, and 24” on-center, however other spacing may be used by a Structural Engineer. Depending on all contributing factors though, roof rafters are 16” and 24” far apart, are commonly used for most residential buildings. The wider the space between rafters often results in rafters of greater depth too.
Rafter sizes
Most common size of dimensional lumber as roof rafter are 2″×6″, 2″×8″, 2″×10″, 2″×12″ and 2″×14″ used in roof framing. Thicker dimensional lumber, such as 2x10s and 2x12s can span further. Thickness of rafter should be not less than 2 inches and their depth should be range from 4″ to 12″. Length of Rafter depending on climatic condition, style, slope and type of structure. It is used over brick external wall, wall plate, over two support and over top of beam.
What size rafter for a 26 foot span
The size of the rafter needed for a 26-foot span have to be 2×12 lumber spaced at 12″ on center. However, it depends on the type of wood, the load it needs to support, and local building codes.
Rafter span
A 2×4 size of roof Rafter can allow to maximum span up to 9 feet when spaced 12″ O.C, up to 8′ 3″ on 16″ O.C, and up to 7′ 3″ on 24″ O.C.
A 2×6 size of roof Rafter can allow to maximum span upto 14′ 6″ when spaced 12″ O.C, 13′ 0″ on 16″ O.C, and 11′ 6″ on 24″ O.C.
A 2×8 size of roof Rafter can allow to maximum span upto 19′ 0″ when spaced 12″ O.C, 17′ 0″ on 16″ O.C, and 15′ 0″ on 24″ O.C.
● How much topsoil do you need per square foot
● How much does a 2 cubic foot bag of mulch weigh
● How much does a cubic foot of gravel weigh
● How many bundles of shingles do i need for a 2000 square foot house
A 2 ×10 size of roof Rafter can allow to maximum span upto 23′ 0″ when spaced 12″ O.C, 19′ 11″ on 16″ O.C, and 16′ 3″ on 24″ O.C.
A 2×12 size of roof Rafter can allow to maximum span upto 26′ 9″ when spaced 12″ O.C, 23′ 2″ on 16″ O.C, and 18′ 11″ on 24″ O.C.
What size rafter for a 20 foot span
The size of the rafter needed for a 20-foot span have to be 2×12 lumber spaced at 16″ on center. However, at 12 inches on center spacing you can use a 2×10 size of lumber as rafter for 20 feet span.
What size rafter for a 22 foot span
The size of the rafter needed for a 22-foot span have to be 2×12 lumber spaced at 16″ on center. However, at 12 inches on center spacing you can use a 2×10 size of lumber as rafter for 22 feet span.
What size rafter for a 24 foot span
The size of the rafter needed for a 24-foot span have to be 2×12 lumber spaced at 12″ on center. However, it depends on the type of wood, the load it needs to support, and local building codes.
Conclusion:
Roof rafter spacing are 12” (300mm), 16” (400mm), 19.2” (500mm), and 24” (600mm) on-center. Most common size of dimensional lumber as roof rafter are 2×6, 2×8, 2×10, 2×12 and 2×14 used in roof framing.