How to Raise a Roof Pitch When Reframing the Roof

Obtain all necessary building permits and check local regulations about roofing requirements. Rent a big dumpster for old roofing and get ladders or scaffolding to use in removing it. Take off the old shingles, decking and other roof covering with pry bars and hammers to expose the existing rafters. Remove the rafters without damaging the wall caps where they are fastened.

Cut new rafters according to the desired pitch, measured in inches per foot of run from outer wall to peak. Make the new pitch conform to snow loads and other factors; a typical pitch in most of the United States will be 5/12 to 7/12, meaning a rise of 5 to 7 inches per foot of run. Go to a 5/12 if converting from a flat or low-slope, to a 7/12 or higher to gain attic space.

Mark the new rafters with a framing square, pencil and tape measure. Put the point of the square at the end of a rafter board. Set the inch mark on the square's tongue for the chosen pitch, 5-inch for a 5/12, for example, at the top of the board with the 12-inch mark on the wide blade aligned at the top of the board. Draw a line down the angle on the tongue at the end of the board for a top or plumb cut.

Determine the length needed with the "length of common rafters" table on the blade. Look under the pitch inch-mark, 5 for a 5/12 roof, which will show 13, meaning each rafter must be 13 inches for every foot of run. Find the run by dividing the width of the roof in two.

Multiply the differential times the run; a 5/12 pitch with a 12-foot run on a 24-foot wide roof, for instance, will require a rafter 156 inches long from peak to wall. Measure that distance with a tape measure on the rafter board and draw a 1-inch vertical line up into the bottom of the rafter. Measure 3 1/2 inches up toward the top cut and connect that point with the top of the vertical line to form a triangle to fit on the wall top.

Add any overhang for an eave on the edge of the roof and draw another angle, the reverse of the top cut; put the square point at the top of the board and repeat the alignment. Cut all those angles with a circular saw and use that rafter as a pattern to cut all other rafters. Find the number needed by dividing the length of the roof by 24 and multiplying by 2; a 24-foot long roof, for instance, will require 10 pairs of rafters or 20 rafters in all.

Go back to the plumb cut, measure 3/4 inch down the board and draw another angle identical to the original to create space for a ridge board between rafters.

Use a ladder to mark the wall caps and ridge board for rafter locations. Measure 1 1/2 inches in from the end wall and draw a line to mark the first rafter spot. Measure 23 1/4 inches in and mark the outside line for the second rafter. Measure 24-inch spaces based on that line to mark other rafter locations to the other end of the roof.

Set the first pair of rafters at the end of the roof. Nail the triangles to the wall cap with 16d framing nails and a hammer, two nails on one side, one on the other. Let the rafter tops lean together. Use a level to set the rafters plumb and brace them with 2-by-4 supports nailed to the rafters and to stakes in the ground.

Place another pair of rafters at the other end of the roof the same way. Set the ridge board in place between the rafter pairs, lifting it from the bottom so rafter tops will help hold it. Make sure it is level and nail the end rafters to the ridge board. Install other rafters in pairs down the roof on the marked spots. Make sure each rafter pair is plumb and the ridge board stays level.

Add hurricane clips on each rafter where it meets the wall cap. Nail these to the wall cap and the rafter with 8d galvanized nails, two nails on each end of the clip.