Rafter Marking Information Technology and Communication Services By Dave Wilson Information Technology and Communication Services ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign Copyright ® 2001 - University of Illinois Board of Trustees GJA

Table of Contents III. Gable rafter marking steps IV. Collar tie A. Marking a collar tie V. Shed Roof Rafters VI. Shed rafter marking steps VII. Parts of a Building I. Purpose II. Gable Roof Rafters A. Ridge piece B. Plate C. Roof slope D. Marking line E. Length of rafter F. Birdsmouth G. Overhang H. Fascia and Soffit I. Types of tails J. Roof pitch table 03 04 05 06 07 10 12 14 15 17 21 22 23 39 40 43 47 61 QUIT Previous Slide Table of Contents Next Slide ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign

The purpose of this presentation is to identify rafter parts, building parts, and one method of marking gable and shed style rafters. The presentation will focus on: identifying gable rafter parts parts of the building required to mark a rafter roof pitch marking a gable rafter identifying shed rafter parts marking a shed rafter ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 03

Gable Roof Rafters Rafter Rafter Gable rafters are normally equal in length, each spanning an equal distance of the building. Exceptions to the rule exist and require only small adjustments to be marked. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 04

Ridge Piece Ridge piece Ridge piece lumber is normally two inch lumber and wide enough to receive the full depth of the rafter. dressed - 1 1/2 inches thick nominal - full cut or 2 inches thick ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 05

Plate Most buildings are constructed with double plates to tie the corners of the building together. The plate directly supports the rafters and will commonly be nailed to the top of the wall studs. Upper plate Wall stud ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 06

Roof Slope Rise Slope triangle C L Span Run Roof pitch is normally given as a triangle, stating the number of inches of rise per foot of run. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 07

Run, Span & Rise of a Gable Roof Run is the horizontal distance under the rafter extending from the outer edge of the building to a plumb line from the center of the ridge piece. Total run of a rafter is 1/2 the span of the building. Span is the distance from one outside wall to the outside wall on the other side of the building. The span is the width of the and is two times the length of the run. Rise is the vertical distance from the top of the plate to the marking line at the ridge piece. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 08

Rise, Run & Span 09 Rise Run Span Centerline ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 09

Marking Line Marking line The marking line is located 1.5 inches from the bottom of a 2-inch x 4-inch rafter and 2 inches from the bottom of 2-inch x 6-inch or larger rafter. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 10

The marking line is drawn onto the rafter pattern prior to marking rafter parts. A common tool used to draw the marking line is the framing square and a lead pencil. The tongue of a framing square is 1.5 inches wide and the blade is 2 inches wide. The marking line is always drawn on the lower side of the rafter, preserving the largest amount of rafter to support the building roof. The marking line can be used as reference line to mark the upper and lower plumb cuts and the depth of the bird’s mouth. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 11

Length of Rafter 12 Rafter length Rafter tail ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 12

Length of Rafter The length of the common rafter is the shortest distance between the outer edge of the plate and the centerline of the ridge piece. The length of each rafter must be adjusted to allow room for the ridge piece. Adjusting rafter length subtracts one-half the thickness of the ridge from each rafter. (Caution is recommended to avoid errors when correcting the length of the gable rafter.) The actual length of the rafter is a bit shorter than the theoretical length of the rafter. The rest of the rafter is called the rafter tail. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 13

Birdsmouth Plate level Birdsmouth 14 Birdsmouth is the name given to the notch cut into the rafter where it is to sit on the plate. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 14

Overhang Outside wall Overhang Fascia line Overhang is measured on a horizontal line. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 15

Overhang The overhang is sometimes called the projection. Overhang is the horizontal distance from the outside wall to the fascia line. When the rafters overhang the building, the overhang helps to form the eaves or cornice and this sheds the water away from the building. The overhang also provides shade to keep the sun from shining on the upper part of the side wall of the building. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 16

Cuts for Trim Fascia Fascia Cut Soffit cut Soffit Plancher level 17 ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 17

Cuts for Trim The vertical cut on the end of the rafter is the fascia cut. The fascia cut is normally plumb. The fascia or trim board is nailed to the rafter along this vertical cut. If the cornice is to be enclosed, the horizontal cut on the rafter is called a soffit cut. The imaginary horizontal line is called the plancher level and sometimes the board that is used to enclose the cornice is called the plancher or soffit. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 18

Gable Rafter Cuts Ridge cut (upper plumb cut) Heel Plumb cut Seat cut Tail cut (lower plumb cut) ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 19

Gable Rafter Cuts The ridge cut is sometimes called the upper plumb cut. This cut must be perpendicular to the earth, hence the name plumb cut. The cut at the lower end of the rafter is called the tail cut. There are different styles of tail cuts. The heel of the rafter sits on the plate and the cut that is parallel to the top of the plate is called the seat cut. The other part of the birdsmouth is a plumb cut and it is marked by applying the square in a similar manner to the way the ridge and tail cuts are made. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 20

Types of Tail Cuts Parallel to Plumb cut Parallel to Seat cut Combination cut Square cut ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 21

Roof Pitches This table gives the pitch for various rises Blade This table gives the pitch for various rises of roof from 1 inch to 24 inches per foot of run. It can be seen from this table that a rafter rise of 12 inches per foot of run is equivalent to 1/2 pitch (12 over 24). This is the same as a 45-degree angle. 12 = 1/2 45º 0´ 1/2 Tongue ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 22

Marking a Gable Roof Rafter Step #1 The example problem will be marked with a 6-inch rise per foot of run. Mark here Dot goes here The dot marks the length of the overhang, 16 inches. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 23

Marking a Gable Roof Rafter Step #1 In this example we have a slope triangle with a 6-12 slope. Step one includes placing the marking line onto the rafter lumber. When marking a rafter using a framing square be alert to use both numbers on the outside of the square or from the inside set of numbers on the square. Starting at the bottom, rafter tail, end of the rafter place the framing square onto the marking line so that the 6 inch mark and the 12 inch mark intersect with the marking line. The 6 inch mark needs to face the outside of the building (lower end of the rafter). ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 24

Marking a Gable Roof Rafter Step #1 Continued Mark the lower plumb cut using a pencil and checking to be sure the square numbers both on the outside or inside of the square and properly aligned on the marking line. While holding the square in this position the back of the birdsmouth or overhang length can be marked. Remember this distance is always horizontal and perpendicular to the plumb line of the outer wall. In the example problem the overhang is 16 inches and marked with a dot on the rafter. It is important to mark the overhang length using the same side of the square as the pitch, 6-12 are being aligned. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 25

Marking a Gable Roof Rafter Step #2 Marking the back of the birdsmouth. Mark here 12 6 ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 26

Marking a Gable Roof Rafter Step #2 Continued Step 2 marks the back of the birdsmouth and can be done without lifting the square from the rafter. The square is slid toward the center of the rafter keeping the pitch, 6-12, lined up on the marking line until the blade of the square intersects the dot from step #1, marking the back of the birdsmouth. Draw a line from the marking line to the bottom of the rafter to create the back of the birdsmouth, this will be a plumb cut and parallel with the lower plumb cut. This can be checked visually. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 27

Marking a Gable Roof Rafter Step #3 Marking the seat cut. 6 12 Mark here ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 28

Marking a Gable Roof Rafter Step #3 Continued Marking the seat cut creates a horizontal line parallel with the top of the plate. Rotate the square so the tongue is facing the center of the rafter. Align the 6 on the tongue and the 12 on the blade of the square with the marking line. Slide the square on the rafter until the outside of the tongue aligns with the intersection of the marking line and the plumb line at the back of the birdsmouth. Draw a line from the back of the birdsmouth to the lower edge of the rafter. This marks the heel of the rafter and is called the seat cut. The triangle created should look similar to a door wedge. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 29

Marking a Gable Roof Rafter Step #4 Dot Calculating rafter length 12 Rafter length 3/4” 6 The dot marks rafter length. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 30

Marking a Gable Roof Rafter Step #4 Continued Gable rafter length is determined using the slope triangle, rafter table (from the framing square), the run of a building, and the thickness of the ridge piece. Rafter length = (Square reading x run) minus 1/2 the thickness of the ridge piece. Look at the framing square and locate the rafter table, front side of the blade. The top line should be labeled “LENGTH COMMON RAFTERS PER FOOT RUN.” Follow the common rafter line to the right to the column of numbers under the 6-inch mark on the outside edge of the blade. The first number should be 13 42, this represents 13.42 inches of rafter length per foot of run. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 31

Marking a Gable Roof Rafter Step #4 Continued The column under the 6 was selected because 6 inches of rise per foot of run equals the pitch of the roof in the example problem. The 13.42 means for each foot of run, the rafter is 13.42 inches long. Calculate the rafter length (for building run) by multiplying 13.42 times the number of feet of run in the building. Measure the rafter length with a steel tape from the corner of the birdsmouth along the marking line. Mark the length with a dot. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 32

Marking a Gable Roof Rafter Step #4 Continued The length of the rafter must now be adjusted for the thickness of the ridge piece. The ridge piece is parallel with the upper plumb cut, therefore the adjustment to the rafter must be parallel to the upper plumb cut. Use the framing square to mark this adjustment. Place the square on the rafter aligning the 6 and the 12 with the marking line. (The tongue, 6-inch mark, should be toward the center of the rafter.) Slide the square along the rafter until the blade intersects the dot marking the length of the rafter. The blade of the square should be parallel with the heel of the birdsmouth. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 33

Marking a Gable Roof Rafter Step #4 Continued With the blade of the square lined-up with the mark indicating rafter length, follow along the blade of the square 3/4 inch toward the center of the rafter, for dressed ridge lumber, marking the rafter with another dot. The rafter was shortened by 1/2 the thickness of the ridge piece. The new dot will represent the adjusted length of the rafter. Mark the spot on the rafter to draw the upper plumb cut. The mark representing the adjusted length of the rafter will not be located on the marking line. The new dot should be located above the marking line toward the top of the rafter. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 34

Marking a Gable Roof Rafter Step #5 Marking the upper plumb cut Mark 6 3/4 inch 12 ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 35

Marking a Gable Roof Rafter Step #5 Continued The square should be placed on the rafter with the blade toward the center of the rafter. Align the 6 and the 12 with the marking line, double checking to use numbers on the same side of the square. Slide the square on the rafter until the tongue intersects the mark indicating the adjusted length of the rafter and draw a plumb line across the rafter using a pencil. Visually check to assure the upper plumb line is parallel to the lower plumb line and the plumb line is marked at the birdsmouth. The seat cut at the birdsmouth should be perpendicular to the plumb line. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 36

Marking a Gable Roof Rafter Step #6 Marking trim cuts Mark Dot 6 12 ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 37

Marking a Gable Roof Rafter Step #6 When a soffit is to be used and you wish to cut the rafters so that the soffit can be nailed to the underside of the rafters OR if you wish to cut the rafter so that it does not extend below the fascia board as shown in slide #37, then mark the soffit cut line following the directions listed below. Apply the square with the 6 and 12 marks on the inside of the square along the lower plumb cut at the marking line. Make a horizontal mark from the marking line to the lower edge of the rafter this will be horizontal to the seat cut at the birdsmouth. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 38

Collar Tie The function of the collar tie is to hold the two rafters together. Collar tie ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 39

Marking a Collar Tie Mark Dot 40 24 12 12 6 ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 40

Marking a Collar Tie If the builder wants to locate the collar tie 12 inches below the ridge piece, he/she would apply the square to the ridge piece or to the upper plumb cut on the rafter. This way the 12 inch mark on the outside of the tongue of the square is even with the lower edge of the rafter and the 24 inch mark on the outside of the blade just touches the lower edge of the rafter. Place a dot on the edge of the rafter at the 24 inch mark. The carpenter then rotates the square and lines the 6 inch and 12 inch marks on the outside of the square even with the upper edge of the rafter. Slide the square up until the blade of the square is even with the dot on the lower edge of the rafter. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 41

Marking a Collar Tie Continued Place a mark across the rafter at this point. This mark will be the horizontal to the heel of the rafter and will be 12 inches below the ridge piece. This is the location for the collar tie. This mark should be made on both rafters and the collar tie can be nailed on these two lines. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 42

Shed Roof Rafter Rafter length Front plate Overhang Marking line Rear plate Overhang ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 43

Shed Roof Rafter A shed roof rafter rests on two fixed points, the rear plate and the front plate. Since the front and rear plates are fixed points, the length of the rafter is measured from the upper edge of the rear plate to the upper edge of the front plate. The front and rear overhang of the rafters must be added to the length of the rafter as shown in the illustration. The rear overhang is measured from the outside of the rear plate while the front overhang is measured from the inside of the front plate. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 44

Run, Span and Rise Shed Roof Rise Run Span 45 ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 45

Run, Span and Rise Shed Roof The rise of a shed roof is the difference in height of the rear and front plates. The run is measured horizontally from the rear edge of the rear plate to the rear edge of the front plate. Although a shed roof slopes on only one direction the run and the span of the rafters are not the same quantities. The span represents the entire width of the building, while the run of the rafter is shown in the illustration. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 46

Marking a Shed Roof Rafter Step #1 The problem for the illustration will have a 2–10 slope and an 8 inch overhang on each end. Dot The dot marks the amount of overhang and the location for the plumb cut in the birdsmouth. Mark ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 47

Marking a Shed Roof Rafter Step #1 Draw a marking line on the rafter. This can be done by drawing along the blade of the square which is held even with the top side of the rafter on 2-inch by 4-inch rafter lumber. Place the square along the bottom side of the lumber if it is a 2 inch by 6 inch or wider member. Notice the pitch is a 2 – 10 slope. Multiples of the pitch ratio can be used with no loss in accuracy. 4 and 20 will be used in the example problem. Place the 4 inch mark and the 20 inch mark on the marking line and mark the lower plumb cut near the end of the rafter. Measure 8 inches over horizontally on the outside of the square and place a dot on the rafter even with the 8 inch mark. This locates the birdsmouth on the rafter. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 48

Marking a Shed Roof Rafter Step #2 Marking the birdsmouth Mark ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 49

Marking a Shed Roof Rafter Step #2 Slide the square up the rafter with the 4 inch and 20 inch marks on the marking line until the dot is just visible on the outside of the square. Place a line from the marking line to the lower edge of the rafter using a pencil. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 50

Marking a Shed Roof Rafter Step #3 Mark ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 51

Marking a Shed Roof Rafter Step #3 Continued Rotate the square, to place the blade facing toward the bottom of the rafter, and place the 20 inch mark and the 4 inch mark on the marking line. Slide the square until the upper edge of the square intersects the mark locating the plumb cut at the back of the birdsmouth. Draw a horizontal line from the back of the birdsmouth to the lower edge of the rafter. This marks the seat cut. Visually check to verify that the birdsmouth is wedge shaped with the seat cut line perpendicular to the plumb cut. All plumb cuts should be parallel. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 52

Marking a Shed Roof Rafter Step #4 Rafter length Mark here Rafter length ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 53

Marking a Shed Roof Rafter Step #4 Continued Shed rafter length is determined by multiplying the square reading, length per foot of run, times the building run in feet. Square Reading x Run = Rafter Length (inches) Measure the distance from the rear corner of the lower plate to the rear corner of the upper plate with a tape measure. This distance is the length of the rafter from one birdsmouth to the other. Mark this distance on the marking line at the upper end of the rafter using a pencil dot on the marking line. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 54

Marking a Shed Roof Rafter Step #4 Continued Mark the upper birdsmouth at the dot marked on the rafter. Arrange the square on the rafter with the blade end facing the top end of the rafter and the 4 inch and 20 inch marks aligned on the marking line. The tongue should be parallel with all plumb cuts. Slide the square on the rafter so the dot, top end of rafter length, is just visible and draw horizontally from the marking line to the bottom edge of the rafter. This line represents the seat cut for the top end of the rafter. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 55

Marking a Shed Roof Rafter Step #5 Marking the top birdsmouth Mark ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 56

Marking a Shed Roof Rafter Step #5 Continued Rotate the square, blade facing the center of the rafter, and place the 4 inch and 20 inch marks on the marking line. Slide the square on the rafter until the tongue, parallel to all plumb lines, intersects the point on the marking line that indicates the inside corner of the upper plate. Draw a line on the rafter at this point marking the plumb cut for the upper birdsmouth on the rafter. Visually check to be certain that all plumb lines are parallel and the horizontal lines are parallel. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 57

Marking a Shed Roof Rafter Step #6 Marking the upper overhang Mark ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 58

Marking a Shed Roof Rafter Step #6 Continued Use the 2 inch and 10 inch marks representing the rise and run of the rafter and slide the square until these inch marks are along the upper edge of the rafter. The overhang for this building is 8 inches from the outside of the plate/stud. This distance plus the width of the plate/stud, 3.5 inches, will determine where to mark the top end of the rafter. (8” + 3.5” = 11.5”) The overhang for this building should be 11.5 inches from the rear of the upper plate. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 59

Marking a Shed Roof Rafter Step #6 Continued Slide the square along the marking line keeping the 4 and the 20 aligned on the marking line, until the distance from the plumb cut of the upper birdsmouth is just visible at the 11.5 inch mark on the square. Draw a plumb line across the rafter marking the upper plumb cut. The upper plumb cut should be plumb and parallel with the lower plumb cut. ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 60

Parts of a Building Rafter Plate Sill The footing, foundation, sill, and stud wall are the supporting structure for the roof (rafters). Foundation Footing ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 61

Prepared by Dave Wilson This set of images was drawn by the Department of Agricultural Engineering, University of Illinois. It may be used to supplement “Using the Carpenter’s Square,” U3009a, available from ITCS Instructional Materials. Prepared by Dave Wilson QUIT ITCS Instructional Materials College of Agricultural, Consumer and Environmental Sciences University of Illinois at Urbana-Champaign 62 GJA