# How do you calculate a rafter run?

## How do you calculate a rafter run?

The length of the rafter is given from the long point of the ridge cut at the top down along the top edge the board to the same plumb cut on the rafter’s notch. The next result is the run. This is the horizontal measurement from the outside of the wall to the inside of the ridge.

What is the rafter length calculator?

The rafter length calculator lets you calculate truss dimensions using two slightly different sets of variables. It all comes down to what information you already have. Usually, that is either the pitch or the rise of the roof.

### How far can a 2×6 rafter span without support?

2-grade 2×6 joists can span up to 10 feet 9 inches from beam to beam when spaced the standard 16 inches apart with a maximum live load of 30 inches per square foot.

How do you calculate roof framing?

For example, if the slope is 4 in 12, and the run is 12 feet, the ridge beam height (M) will be 4 feet. The finished ridge beam height (Z) above the top of the wall will be (M) plus the Y Height. The formulas are: M = (R * X) / 12.

## What is the maximum span for a 2×4 rafter?

A 2×4 can span a maximum of 6′ 7” when spaced 16” apart and used as a floor or deck joist. When used as a ceiling joist or a roof rafter, a 2×4 can span up to 7′ 3” spaced at 16”, and 6′ 4” when spaced 24” apart.

What is the normal spacing for rafters?

Standard industry roof rafter spacing is 12”, 16”, 19.2”, and 24” on-center, however other spacing may be used by a Structural Engineer. 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.

### Do you need a Birdsmouth on a rafter?

Structurally, a rafter sitting on an angular bearing point (the inclined plane of the ripped strip) would require that the rafter-plate connection deal with the horizontal and vertical components of the force differently than with a birdsmouth.

How far apart should rafters be?

## Can a 2×6 span 12 ft?

A 2×6 can support up to 50 pounds per square foot of weight without sagging with a maximum span of about 12 feet when spanning a distance horizontally, with the 2×6 standing in a vertical position.

What size rafters do I need for a 12 foot span?

Rafter size for 12 foot span:- as per general rules and guidelines, rafter made of pine wood, for a 12 foot span, size of rafter should be 2″×6″ in which thickness of rafter is 2″ and their depth range is 6 inches.

### How to make a common rafter?

Lumber stock

• Framing square or speed square
• Pencil
• Saw
• Measuring tape
• Hammer and nails or a nail gun
• At least one helper
• A construction calculator (optional)
• How to figure rafter angle?

The roof height is the distance from the level of the “floor” of the attic to the roof ridge.

• Roof width — distance between the points of support of the rafters.
• Roof overhang — the distance from the edge of the wall to the edge of the roof.
• Width rafter width rafter boards (usually 10 – 15 cm).
• Thickness rafter thickness rafter boards (usually 5 cm)
• ## How do you calculate rafter length?

● measure the vertical height of rise of your roof, assuming it is 2.5 meters. ● Calculate the rafter length, as Rafter^2 = rise^2 + run^2, Rafter^2 = 2.5^2 + 10^2, Rafter^2 = 6.25+100, rafter = √106.25, Rafter = 10.31 meters, hence rafter for pitched roof will be 10.31 meters.

How to calculate your rafter length?

Go old school&use a scientific calculator and trigonometry (complicated unless you are a maths wiz)

• When I pitch a small roof like a shed or dormer,I often just draw and set the rafter lengths out on a sheet of ply – no need for
• For larger roofs though,I use a roofing ready reckoner.