🏗 Roof Framing Calculator
Estimate rafter length, ridge board, and total lumber for gable or hip roofs
| Width | 3:12 | 4:12 | 5:12 | 6:12 | 8:12 | 10:12 | 12:12 |
|---|---|---|---|---|---|---|---|
| 12 ft | 6.18 | 6.33 | 6.50 | 6.71 | 7.21 | 7.81 | 8.49 |
| 16 ft | 8.25 | 8.44 | 8.66 | 8.94 | 9.62 | 10.41 | 11.31 |
| 20 ft | 10.31 | 10.54 | 10.83 | 11.18 | 12.02 | 13.02 | 14.14 |
| 24 ft | 12.37 | 12.65 | 12.99 | 13.42 | 14.42 | 15.62 | 16.97 |
| 28 ft | 14.43 | 14.76 | 15.16 | 15.65 | 16.83 | 18.23 | 19.80 |
| 32 ft | 16.49 | 16.87 | 17.32 | 17.89 | 19.23 | 20.83 | 22.63 |
| 40 ft | 20.62 | 21.08 | 21.65 | 22.36 | 24.04 | 26.03 | 28.28 |
| Pitch | Rise per Foot | Angle (degrees) | Pitch Factor |
|---|---|---|---|
| 3:12 | 3 in | 14.04° | 1.031 |
| 4:12 | 4 in | 18.43° | 1.054 |
| 5:12 | 5 in | 22.62° | 1.083 |
| 6:12 | 6 in | 26.57° | 1.118 |
| 8:12 | 8 in | 33.69° | 1.202 |
| 10:12 | 10 in | 39.81° | 1.302 |
| 12:12 | 12 in | 45.00° | 1.414 |
| Length | 12 in OC | 16 in OC | 24 in OC |
|---|---|---|---|
| 20 ft | 42 | 32 | 22 |
| 24 ft | 50 | 38 | 26 |
| 30 ft | 62 | 48 | 32 |
| 40 ft | 82 | 62 | 42 |
| 48 ft | 98 | 74 | 50 |
| 60 ft | 122 | 92 | 62 |
Roof framing is one of the most hard and confusing parts of housing, but good planning helps a lot. It is made up of the internal structure that bears the weight of the roof and gives it form. That includes rafters, roof trusses, beams and ceiling joists, that all bind to the exterior walls and together back the covering
There are five main styles for roof framing: shed, gable, hip, gambrel and mansard. For simple gable or shed roofs, you seriously learn the basic building rules. Even so, there are many ways to build a gable roof, which can be too komplice.
Roof Framing Basics and Types
You usually frame roofs by two methods: with pre-manufactured trusses or with rafters and ceiling joists, which commonly calls stick framing. Today, the pre-manufactured trusses are the most popular. Because they are done in factory, they use thinner timbers than traditional framed roofs, are more lightweight, cheaper and faster to erect.
The main advantage is that they only require the exterior walls to form the roof. Like this, you widely do not require supporting walls in the habitable space. In contrast, rafter-type framed roofs commonly require some internal support.
Only around the early 90s pre-manufactured trusses became available in some regions. Before that, every rafter and ceiling joist were done manually. When they first appeared, you could use them only for around 70 percent of a complex house.
In recent years, even so, it is possible to use them for almost 100 percent.
The simplest way is use premade trusses, but if you build rafters, you start by pinning the ceiling joists every 16 or 24 inches, usually the latter. When you build houses with trusses for hips and valleys, careful planning and good organization of the job-site are key for efficient implementation. Measurement of the bottom edge of the rafter helps to do right plan.
A roof framing plan shows the whole structure: roof trusses, rafters, purlins, hip beams, valley beams, ridge beams and ceiling joists. It should have notes about the dimensions of the timbers, the intervals and other demands. The framing must be done exactly as written in the plan, otherwise it will not pass the technical control.
If you use the central line to count the long of the rafter, recall reduce half part of the ridge thickness from the result. Counting the corners and offsets for irregular hips or valley parts are a difficult task. “Bastard-beam” is any hip or valley that backs different slopes of the roof.
Building the roof is the last step of the framing of a new house. Advice of expert builders make the learning easier and help more quickly reach the result.
