The first step in roof framing is to make a plan and then cut out the rafter pattern. The way roof rafter rises and slopes will indicate the height of the ridge board, the valley rafters length and all the other elements of a conventional roof with a frame.
Usually roof frames are made by professional carpenters with expertise in frame construction. The skill is very special one and takes years of training and experience gained on the field of roof framing to create the best examples of this. Sadly, the craft is dying out. It’s being replaced by the now popular truss roofs. Conventional framing which has been around for several centuries is now getting overshadowed by modern developments where you get pre-fab roofs. But, where you need a lot of customization in framing still rules the roost.
These techniques are useful when creating extra space by adding garages, shed or similar structures to an existing structure. The costs of delivery are lower and they can work with space constraints. These are also much lighter than truss roofs. To learn more about calculating the length of rafter needed for roof framing just follow the steps outlined below.
Designing Roof Framing Rafters
A common rafter in framing has several parts called the tail cut, birdsmouth cut, plumb cut, wall stud, ridge board, ceiling joist and many more. Measuring for roof rafters has to start with calculating the pitch, length of rafter, spacing between rafters and lumber size.
The overall width of the your building is determined by measuring the span of framing rafter. This is the point where the rafters will sit. On the other hand the run is half of this span measured earlier. This horizontal distance is what your rafter will run to meet the one from opposite side.
Lumber Length For Roof Rafters
When selecting lumber length you need to choose one keeping in mind the horizontal run of the rafter. Do not base it on length or the span of the rafter. A roofing calculator can be used to measure the length of the rafter. Several websites have online roofing calculators available to make this calculation easy for you. For the ridge board you will need to use the next larger size of lumber than the rafters. You also need to keep in the mind the length of the eaves when ordering lumber.
Find lumber that is straight, long and light. Create a pattern for your roof framing. You will be needing many rafters for your roof frame design. So, selecting lighter lumber will be a welcome decision that will save lots of energy when hauling them up to the roof level.
Mark the length carefully on the lumber and cut at the proper angle. Also, mark the outside edge of your building on the rafter. To do this you will need a plumb line. Place a framing square and mark it using the plumb line to indicate the outside edge.
Creating Birds mouth
An important cut in the rafters called the birdsmouth cut helps the rafters to rest on the outside wall of the buildings. Unless the cut it at least 4 inches the rafter can not achieve full bearing. This can be achieved by sliding the framing square along the rafter until you get the desired cut depth on the rafter that you have marked out earlier.