If you add an eaves overhang dimension then the amount the rafter sticks passed the wall will be added to the rafter length. Stair tangent for iphone this iphone app is for rough frame carpenters that dont build stairs everyday, but could use an stair app calculator to check their stair building calculations. Set bottom cut over edge of plate and in line with ridge. Roof rafter length cutting a rafter birdsmouth to convert rafter span to sloping distance. A carpenters framing square includes some tables stamped right into the tool itself. Determine the pitch of the roof, which is the angle that rafters rise from the outside walls to the ridge. The ridge is in the middle so figure 12 the building width is 12. Since we know our pitch is a 6 in 12, look along the top edge of the square at the 6 mark. Lets figure the rafter length for an 18 in 12 roof. Roof pitch is measured in a rise to run ratio, with the vertical rise always shown first. The common rafter length can be calculated by the roof ratio length per 12 of run.
Complete instruction book and rafter length tables. If u have a framing square, it will give the length of common rafter on it long leg. Framing square rafter table guide how to figure roof rise. So if your roof is a 45 degree angle that is, for every 12. For a run greater than that given in the tables, add any two runs that will equal the desired run, then find the respective lengths for those two rafters and add them together. Sep 22, 2016 once you know the length of the rafter, how do you correctly mark the angle to cut where the rafter meets the ridge top board. You can make ads in the engineering toolbox more useful to you. Roof pitch is designated by a set of numbers, such as 4 12 or 6 12.
A ready reckoner is pretty much a rafter length calculator a book full of tables for. Press the diagonal key, which will calculate the diagonal measurement between your structures outside wall and the top of the ridge beam. Hap rafter table for all material sizes and pitches. Sponge, look on your framing square under the 6 and it will show you the theoretical rafter length per foot of run. Rafter is a sloping beam usually wood that supports a pitched roof. Once inch rise and run are calculated, use the tables in the back of this book to find common rafter length. The script also returns passed or failed for the d4 and rule for rafter bearing above the plate line. The word pitch is often misused, as in this and many other articles. Pitch 0 12 inches 12 12 span feet inches sixteenth.
On the framing square blade face, using the common rafter length per foot run line in the table, look along the blade under the inch number 18 we see 21. If u are making a gable roof, the height of the ridge will be 36 above top plate. Click the button to calculate the stock size needed for this job. One of users asked us to create calculator which will help him estimate hip roof parameters, like rafters lengths, roof rise and roof area. If you add an eaves overhang dimension then the amount the rafter sticks passed the wall will be. In the gableroof example shown here, a rafter with 6in12 pitch rises 6 in. If youre framing a gable roof on a new house, or building a shed or even a doghouse with a gable roof, youll need to cut a number of roof rafters. The building width is 24 with a 612 pitch and a 12 eave and 2 by 6. The most useful book ever if you want to cut a roof. Irwin rafter square reference guide complete instruction book. You put in the width and the pitch and this book will give you the full length of the rafter. How to measure roof rafters including the pitch and birds. Roof pitch, rafters and how to calculate angles my old workshop.
The tail or eave overhang must be added to the rafter length. Use the pythagorean theorem to calculate the rafter length. This article explains how to make quick use of a framing square and its imprinted data to get some basic roof measurement data like roof pitch or slope, rafter lengths, and end cuts. Each page has a different table depending on the pitch angle of your roof with all the figures you need. Hip or valley rafter for same roof to be marked with a square or bevel 6x1611 12 and 8144 inches, length of rafter measures from a to b 18 9 1 12 inches, as shown on fig. A rafter that sets on top of the main roof without cutting into the. Lay device on incline and hit start measuring to directly measure pitch. One might say that its a 612 pitch this is incorrect.
How to calculate roof rafter lengths carpentry tips and tricks. Includes result for hipvalley factor, slope factor and the roof slope in degrees. Visit the roof framing page for more information on cutting roof rafters, and visit the roof pitch calculator for. Includes result for hipvalley factor, slope factor and. The upper fascia for a custom raised gambrel will always be square cut. I dont have a book of common rafters to look up the info. The full outside lenght is 16 feet 4 12 inches and needs to have a pitch of 612.
Using the pythagorean theorem, a2 b2 2 c, the unit run of a hip rafter is the square root of 144 144 which is 16. Then you need to adjust for ridge thickness and seat cuts. This calculator helps you make the rafters of the suitable sizes required for your roofing. Roof pitch refers to the amount of rise a roof has compared to the horizontal measurement of the roof called the run. For larger roofs though, i use a roofing ready reckoner. The complete pocket reference to roof framing 2nd edition. Slope the slope of a roof is represented as x 12, where x is the number of inches in rise for every 12 inches of run. Your custom dimension h at this point you will decide how much overhang you want on your shed. This calculator is to be used as an estimating tool only. The hip and valley factor is a number that is multiplied by the actual run horizontal distance of a common rafter to determine the length of a hip or valley rafter. For every 12 inches of run, the roof will rise 10 inches. We will be figuring the pitch, rafter length, lumber size, and on center spacing for the rafters. Jun 16, 2017 the most useful book ever if you want to cut a roof.
How to calculate rafter lengths for gable, hip and valley. The traditional method has been rise inches12 run inches. Basic roof framing instructions carpentryproframer. Slope the slope of a roof is represented as x12, where x is the number of inches in rise for every 12 inches of run. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. Our roof rafter calculator tools are handy for calculating the number of rafters needed, rafter length calculator, lineal feet of rafter, board feed in ridge and subfacia,and the total board feet in the roof. The first number represent the amount in feet that a rafter rises. The 6 side is the plumb cut that goes to ridge board. Nov 09, 2012 121 responses to common rafter framing bill bartlett november 9, 2012. Length of rafter measures from a to b 5 6 144 inches, as shown on fig. You can use a framing table or website to calculate your rafter lengths. Easily move materials across solid or soft surfaces these carts are constantly in use in our shop. The metric method for slopes less than 45 degrees shows the first number as 1 all the time, so a. How to calculate rafter lengths for gable, hip and valley rafters.
The overall length of the roof or a common rafter, from the base to the ridge, is calculated by squaring the run, adding it to the square of the rise, and finding the square root of the sum. Also referred to as 612 roof slope, 6 on 12, 6 to 12 and 612 roof angle. Invaluable to anyone who wants to cut a roof by hand and not use trusses. Divide the rafter length by 12 of run to calculate the roof ratio multiplier. The second number is the benchmark for typical pitched roof calculations. Just under the 6 mark in the first row,you will see.
If you find this website valuable and appreciate it is open and free for everybody please contribute by. Using the 7 inch rise table and our 15 run, the common rafter length is 17 43. This height above plate rafter script calculator will return the h. Once you know the length of the rafter, how do you correctly mark the angle to cut where the rafter meets the ridge top board.
How to lay out a hip rafter explained by a holly hill sc home. A ready reckoner is pretty much a rafter length calculator a book full of tables for working out the rafter lengths quickly and easily. What is rafter length for a 12 foot wide building with a. The roof pitch calculator calculates slope, pitch, angle and rafter lengths, based on input of rise m and run r. Visit the roof framing page for more information on cutting roof rafters, and visit the roof pitch calculator for determining rafter lengths based on rise and run. Use the calculator below to determine rafter length. Select plumb, square, or level from the fascia type dropdown list. How to lay out a hip rafter explained by a holly hill sc.
Subtract what you are using as a ridge and you have your length perfect every time. To see how pitch impacts the look of a garage and changes cost click the design center button on our pole barn kits page. Hip or valley rafter for same roof to be marked with a square or bevel 6x161112 and 8144 inches, length of rafter measures from a to b 18 9 112 inches, as shown on fig. Input the rafter span on the flat, eave overhang and pitch of the roof. Rise and run means that a 612 pitch roof has 6 of rise vertical for each foot of run horizontal. These roof framing books were written to make complex roof framing simple. What is rafter length for a 12 foot wide building with a 12.
To figure out the rafter length from ridge to the seat cut, you take the run and times it by the number 6 pitch on the framing square, minus 34 which is 12 the thickness of the ridge. Thinking my ridge beam height should be 49 12 inches from the top of the garage walls with the 612 pitch. Roof pitch calculator calculates pitch, rafter length. The complete pocket reference to roof framing 2nd edition barry d. If slope is 4 in 12 and rafter span is 126, then sloping distance 12. Length of rafter measures from a to b 5 6144 inches, as shown on fig.
Roof pitch, rafters and how to calculate angles my old. This is the rafter length from the top cut to the seat plumb mark. Calculate the length of a rafter from the roof slope ratio of inches per foot, and a building width measurement. Center to center rafter spacing inches rafter thickness. Horizontal span of rafter inches,run roof pitch inches rise, e. What is rafter length for a 12 foot wide building with a 12 12 pitch. Enter the value for the roof width outside to outside in feet, inches, and fraction, inches and fraction, or use the inches box to enter a value in decimals if that is your preference. Diagrams are included throughout the book to assist in the use of the speed square for roof construction and other. The top rafter tab displays a dimensioned side view of the. It is marked on the left side of the row with this description length common rafters per foot run. The bottom rafter tab displays a dimensioned side view of the gambrel roof bottom rafter. How to layout and cut hip and valley roof rafters youtube. Use the diagrams on this page as a reference when inputting rise and run, and while interpreting the calculated results.
Laying out hip, valley, and jack rafters takes experience and skill, but if youre building a simple gable or shed roof, all you need is the common rafter, the basic building block of roof framing to lay out a common rafter, you need the pitch of the roof, expressed in units of rise per foot of run. Or i can tell you the rafters should be 45 58 long from ridge to seat cut. Use our online rafter length calculator to quickly compute the length of the shed roof rafter by entering the measurements of overhead, length of roof span, pitch or angle. This setting only applies to the lower rafter fascia. Simply read across until you find your pitch and multiply that number by the run in feet. Rafter span tables use these tables to determine lengths, sizes and spacing of rafters based on a variety of factors such as, species, load, grade, spacing and pitch. Publisher is not liable for errors or omissions in this book. The roof rafters provide integral structural support to the roof.
The full outside lenght is 16 feet 4 12 inches and needs to have a pitch of 6 12. The picture below shows the pitch of a 712 roof slope meaning that for 12 of horizontal measurement. Jul 09, 2017 how to layout and cut hip and valley roof rafters. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. For a roof with 16 pitch or the rise 16 the width of the building and having a run of 12 feet. This table provides the hip and valley factor for common roof pitches, as well as the underlying equation for the factor. Like the unit length of a common rafter, the unit length of a hip rafter may be obtained from the rafter table on the framing square. If slope is 4 in 12 and rafter span is 12 6, then sloping distance 12. Deduct half the thickness of the ridge from the span length this length. This is very useful information for many purposes, especially for roof framing the slope, sometimes called pitch, is calibrated on speed squares. Take a regular length common rafter such as used on main roof. If youre using a roofing calculator, it will use the information youve already input run measurement and pitch to calculate the length for each rafter. To get results you need to provide roof base dimensions length and width and roof pitch we assume it is identical for all sides.