How far can a 2″×4″, 2″×6″, 2″×8″, 2″×10″, 2″×12″ Rafter span

How far can a 2″×4″, 2″×6″, 2″×8″, 2″×10″, 2″×12″ Rafter span | what is the maximum span for a 2×6, 2×8, 2×10, 2×12 and 2×14 rafter | What is the maximum span for a 2″×6″ rafter | maximum span for a 2″×8″ rafter | maximum span for a 2″×10″ rafter | maximum span for a 2″×10″ rafter | maximum span for a 2″×12″ rafter | maximum span for a 2″×14″ rafter.

How far can a 2"×4", 2"×6", 2"×8", 2"×10", 2"×12" Rafter span
How far can a 2″×4″, 2″×6″, 2″×8″, 2″×10″, 2″×12″ Rafter span

A rafter is sloping roof member or one of a series of sloped structural members made of wooden beams or steel that extend from the ridge or hip of roof structure to the wall plate, downslope perimeter or eave, and they are designed to support the roof load, roof shingles, roof deck and its associated loads. A pair of rafters is called a couple.

When you want to design and building a roof for house, a shed, porch, cabin, garage, or home can be a huge task. What size rafter we use, their spacing, wood species, lumber grade #1, #2, #3, to consider dead, live, wind load, and snow loads, selection of the correct species, lumber grade, and dimension of lumber for the rafter span, and decide if there will be a ceiling or loft supported by the rafters.

You have to select the correct rafter size and spacing to span the distance from hip to wall based on all the factors that affect your design.

Standard roof rafter spacing is 12 inches, 16 inches, 19.2 inches, and 24 inches on-center, however other rafter spacing may be used which are designed by a Structural Engineer. Depending on all many factors though, 16 inches and 24 inches spaced are commonly used for most buildings. The wider the space between rafters often results in rafters of greater depth too.

Rafter size: most common size of dimensional lumber which are used as roof rafters are 2×4s, 2×6s, 2×8s, 2×10s, 2×12s and 2×14s. Thinner dimensional lumber 2×4s, 2×6s, 2×8s can span further at 12″ or 16″ on centers other hand thicker dimensional lumber, such as 2x10s, 2x12s and 2×14s can span further at 24” centers. The greater the space between rafters, the shorter the distance they can span.

In this article we know about “How far can a 2″×4″, 2″×6″, 2″×8″, 2″×10″, 2″×12″ & 2″×14” Rafter span and what is the maximum span for a 2×4, 2×6, 2×8, 2×10, 2×12 and 2×14 rafter. Maximum allowable span for rafter depending on many factors, wood species, lumber grade, variable loads, location, roof load, live load IRC code book.

What is roof rafter

A Roof rafter is defined as one of a series of sloped structural member typically made from wooden beams that extend from the hip or ridge to wall plate or eave, or downslope perimeter. They are designed to support the roof deck, roof shingles, and everything else that goes with the roof. Its are the traditional way to frame a roof.

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Size of roof rafter

In United states, most common and standard size of roof rafter is 2×4s, 2×6s, 2×8s, 2×10s, 2×12s and 2×14s. Thinner dimensional lumber 2×4s, 2×6s, 2×8s can span further at 12″ or 16″ on centers on other hand thicker dimensional lumber, such as 2x10s, 2x12s and 2×14s can span further at 24” centers.

In UK, most common and standard size of roof rafter in mm which are used in industry is 100×47 mm, 125×47 mm, 150×47 mm, 200×47 mm, 250×47 mm, and 300×47 mm. Size of rafter describe by depth and width. Width of rafter is not less than 2 inches and depth of rafters range from 4 inches to 14 inches thick.

Roof rafter spacing

Spacing between the rafters are 12”, 16”, 19.2”, and 24” on center. In North America,
the International Residential Building Code (IRC), which is the basis of most building codes, identifies the standard spacing between rafters as 12”, 16”, 19.2”, and 24” on center. Though, most commonly used 16″ and 24″ spaced for most buildings.

How far can a 2″×4″, 2″×6″, 2″×8″, 2″×10″, 2″×12″ Rafter span

Roof rafter maximum span depending on wood species, lumber grade #1, #2, #3, rafter span, live and dead loads on the roof, deflection, wind and snow loads, and whether a ceiling will be attached or not.

Additional factors include slope, eave and rake overhangs, roof tie-downs, rafter support bracing, collar ties, ridge connection, roof openings, ventilation, and roof finish. Live and snow loads vary from 10 to 70psf with dead loads of 10 and 20psf and deflections of L/∆=180 and L/∆=240.

As per general rules and guideline, a 2″×4″ rafter can allow to span a maximum distance of 9 feet 0 inches when spaced 16″ apart on centre. A 2″×6″ rafter span 13 feet 6 inches, a 2″×8″ rafter span 17 feet 0 inches, a 2″×10″ rafter span 20 feet 3 inches, a 2″×12″ rafter span 23 feet 10 inches, when spaced at 16″ apart from centre.

How far can a 2″×4″ rafter span without support

Maximum span for a 2×4 rafter: maximum allowable span for a 2×4 rafter is 9 feet 0 inches when spaced at 16″ apart from centre, 10 feet 4 inches at 12″ OC, and 7 feet 4 inches at 24″ OC, without support with best quality No. 2-grade southern pine lumber with a maximum live load of 20 pounds per square foot (lbs/ft2) and a dead load of 10 psf.

How far can a 2″×4″ rafter span: A 2×4 size of dimensional lumber as roof Rafter, made of southern pine, lumber grade #2, can allow to span a maximum distance of 9 feet 0 inches when spaced 16″ apart on centre, 10 feet 4 inches distance at 12″ OC and 7 feet 4 inches distance at 24″ OC when Live load = 20 psf, dead load = 10 psf and deflection L/∆ = 180.

How far can a 2″×6″ rafter span without support

Maximum span for a 2×6 rafter: maximum allowable span for a 2×6 rafter is 13 feet 6 inches when spaced at 16″ apart from centre,15 feet 7 inches at 12″ OC, and 11 feet 0 inches at 24″ OC, without support with best quality No. 2-grade southern pine lumber with a maximum live load of 20 pounds per square foot (lbs/ft2) and a dead load of 10 psf.

How far can a 2″×6″ rafter span: A 2×6 size of dimensional lumber as roof Rafter, made of southern pine, lumber grade #2, can allow to span a maximum distance of 13 feet 6 inches when spaced 16″ apart on centre, 15 feet 7 inches distance at 12″ OC and 11 feet 0 inches distance at 24″ OC when Live load = 20 psf, dead load = 10 psf and deflection L/∆ = 180.

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How far can a 2″×8″ rafter span without support

Maximum span for a 2×8 rafter: maximum allowable span for a 2×8 rafter is 17 feet 0 inches when spaced at 16″ apart from centre,19 feet 0 inches at 12″ OC, and 15 feet 0 inches at 24″ OC, without support with best quality No. 2-grade southern pine lumber with a maximum live load of 20 pounds per square foot (lbs/ft2) and a dead load of 10 psf.

How far can a 2″×8″ rafter span: A 2×8 size of dimensional lumber as roof Rafter, made of southern pine, lumber grade #2, can allow to span a maximum distance of 17 feet 0 inches when spaced 16″ apart on centre, 19 feet 0 inches distance at 12″ OC and 15 feet 0 inches distance at 24″ OC when Live load = 20 psf, dead load = 10 psf and deflection L/∆ = 180.

How far can a 2″×10″ rafter span without support

Maximum span for a 2×10 rafter: maximum allowable span for a 2×10 rafter is 20 feet 3 inches when spaced at 16″ apart from centre,23 feet 5 inches at 12″ OC, and 16 feet 6 inches at 24″ OC, without support with best quality No. 2-grade southern pine lumber with a maximum live load of 20 pounds per square foot (lbs/ft2) and a dead load of 10 psf.

How far can a 2″×10″ rafter span: A 2×10 size of dimensional lumber as roof Rafter, made of southern pine, lumber grade #2, can allow to span a maximum distance of 20 feet 3 inches when spaced 16″ apart on centre, 23 feet 5 inches distance at 12″ OC and 16 feet 6 inches distance at 24″ OC when Live load = 20 psf, dead load = 10 psf and deflection L/∆ = 180.

How far can a 2″×12″ rafter span without support

Maximun span for a 2×12 rafter: maximum allowable span for a 2×12 rafter is 23 feet 10 inches when spaced at 16″ apart from centre,30 feet 2 inches at 12″ OC, and 19 feet 6 inches at 24″ OC, without support with best quality No. 2-grade southern pine lumber with a maximum live load of 20 pounds per square foot (lbs/ft2) and a dead load of 10 psf.

How far can a 2″×12″ rafter span: A 2×12 size of dimensional lumber as roof Rafter, made of southern pine, lumber grade #2, can allow to span a maximum distance of 23 feet 10 inches when spaced 16″ apart on centre, 30 feet 2 inches distance at 12″ OC and 19 feet 6 inches distance at 24″ OC when Live load = 20 psf, dead load = 10 psf and deflection L/∆ = 180.

Conclusions:

A 2″×4″ rafter can allow to span a maximum distance of 9 feet 0 inches, a 2″×6″ rafter span 13 feet 6 inches, a 2″×8″ rafter span 17 feet 0 inches, a 2″×10″ rafter span 20 feet 3 inches, and a 2″×12″ rafter span 23 feet 10 inches, when spaced at 16″ OC.

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