The size of rafter depends upon these factors wood type, load that comes on the rafter, and local building codes. But in this article, we will know the standard **rafter size for 10, 12, 14, 15, 16, 18, 20, and 24-foot spans**.

**What is rafters**

The rafter is a structural component that is a series of slopped beams that support the shingles, and roof deck. The rafters can made up of LVL beams, timber, steel, concrete, etc. But generally, rafters are made of **LVL beams** or timber. A rafter starts from the ridge or hip of the roof and ends at the wall plate of the external wall.

## Rafter size for 10, 12, 15, 16, 18, 20, and 24 foot span

The rafter is a structural component of the sloping roof and the sloping roof is most commonly used in snowfall and heavy rainy areas. The size of the rafter depends upon many factors like the load that comes on the roof, live load, dead load, grade of timber, wood species, etc. The rafter size of the snowing area is bigger than the rainy area rafter size. According to load condition size of the rafter can be different in different climate conditions. But we will know about in this article the standard size of rafter for different lengths of span.

### What size rafter do I need for 10-foot span?

For a 10-foot span, we need a 2×6 size rafter according to the basic rules and guidelines, and rafter-to-rafter spacing should be 24″ OC. Here 2 is the width of the rafter and 6 is the depth of the rafter and it should be in inches.

But if we will use 2×4 size rafter for a 10-foot span. Then rafter-to-rafter spacing will decrease and it will be 16″ OC. This size of rafter for a 10-foot span is only valid by using the number 1 grade lumber whose live load capacity is 40lb/ft^{2} and the dead load capacity is 15 PSF.

### What size rafter do I need for 12-foot span?

For a 12-foot span, we need a 2×6 size rafter according to the basic rules and guidelines, and rafter-to-rafter spacing should be 16″ OC. Here 2 is the width of the rafter and 6 is the depth of the rafter and it should be in inches.

This size of rafter for a 12-foot span is only valid by using the number 1 grade lumber. Whose live load capacity is 40lb/ft^{2} and the dead load capacity is 15 PSF.

### Rafter size for 15-foot span

According to basic rules and guidelines for a 15-foot span, we need a 2×8 size rafter, and rafter-to-rafter spacing should be 16″ OC. Here 2 is the width of the rafter and 8 is the depth of the rafter and it should be in inches.

This size of rafter for a 15-foot span is only valid by using the number 1 grade lumber. Whose live load capacity is 40lb/ft^{2} and the dead load capacity is 15 PSF. This is the most suitable rafter size for a 15-foot span.

### Rafter size for 16-foot span

According to basic rules and guidelines for a 16-foot span, we need a 2×8 size rafter, and rafter-to-rafter spacing should be 16″ OC. Here 2 is the width of the rafter and 8 is the depth of the rafter and it should be in inches.

This size of rafter for a 16-foot span is only valid by using the number 1 grade lumber. Whose live load capacity is 40lb/ft^{2} and the dead load capacity is 15 PSF. This is the most suitable rafter size for a 16-foot span.

### Rafter size for 18-foot span

According to basic rules and guidelines for an 18-foot span, we need a 2×10 size rafter, and rafter-to-rafter spacing should be 16″ OC. Here 2 is the width of the rafter and 10 is the depth of the rafter and it should be in inches.

This size of rafter for an 18-foot span is only valid by using the number 1 grade lumber. Whose live load capacity is 40lb/ft2 and the dead load capacity is 15 PSF. This is the most suitable rafter size for an 18-foot span.

### Rafter size for 20-foot span

According to basic rules and guidelines for a 20-foot span, we need a 2×10 size rafter, and rafter-to-rafter spacing should be 16″ OC. Here 2 is the width of the rafter and 10 is the depth of the rafter and it should be in inches.

This size of rafter for a 20-foot span is only valid by using the number 1 grade lumber. Whose live load capacity is 40lb/ft^{2} and the dead load capacity is 15 PSF. This is the most suitable rafter size for a 20-foot span.

### Rafter size for 24-foot span

According to basic rules and guidelines for a 16-foot span, we need a 2×12 size rafter, and rafter-to-rafter spacing should be 16″ OC. Here 2 is the width of the rafter and 12 is the depth of the rafter and it should be in inches.

This size of rafter for a 24-foot span is only valid by using the number 1 grade lumber. Whose live load capacity is 40lb/ft^{2} and the dead load capacity is 15 PSF. This is the most suitable rafter size for a 24-foot span.

#### Conclusion

In this article, we have learned for a 10-foot span we need a 2″×6″ size rafter, for a 12-foot span we need a 2″×6″ size rafter, for a 15-foot span we need a 2″×8″ size rafter, for 16-foot span we need a 2″×8″ size rafter, for 18-foot span we need a 2″×10″ size rafter, for 20-foot span we need a 2″×10″ size rafter, and for 24-foot span, we need a 2″×12″ size rafter.