Sheathing a roof involves the process of installing exterior grade plywood or
OSB waferboard to the roof rafters or trusses. The required plywood or OSB
thickness will depend upon your local building code requirements, but typically
it ranges from 3/8th to 3/4th inch thick.
How Much Roof Sheathing is Required
Measure the number of square feet of roof and divide by 32. There is 32 square
feet in a 4x8 sheet of plywood or OSB. Then multiply this number by 1.15 and
round up to the next hole number to determine the number of sheets to buy and to
allow for an extra 15% of waste.
Tools Required for Sheathing a Roof
To sheath a roof you will need a chalk line, tape measure, claw hammer, circular
skill saw and some ladders. I also highly recommend a nail gun and compressor.
Sheathing a roof requires a great deal of nailing and a nail gun can really help
to speed up the process as well as save on the forearm muscles.
Installing Roof Sheathing
First, the sheathing should be installed perpendicular to the roof rafters or
Second, sheath a roof one slope at a time. Third, sheathing should be
installed starting at the eaves (outside edges) of the roof and then working your
way up towards the roof ridge. However, before installing the first course of
sheathing check to make sure that the roof rafter tails (outside ends) are
straight. If they are not, snap a chalk line along the length of the eaves near
the very edge of the roof rafter/truss tails to make sure you have a straight
and perpendicular line to begin your first course of sheathing.
You can then trim each roof rafter tail relative to the snapped chalk line
using your circular skill saw.
When installing the roof sheathing panels, make sure that they are installed so
that their ends line up over the center of each roof rafter or truss so that you
have a nailing surface for fastening abutting panels.
When it comes to fastening the roof sheathing panels to the roof
rafters/trusses, typically nails should be applied every 6 inches along the
edges of the panels, and every 12 inches in the center field of the panels.
This said, hold off nailing the vertical edges of the panels until you have
installed the adjacent panels. This way you can flex the rafters if necessary to
center them up underneath the abutting roof sheathing panels. Once you have
checked that the roof rafters are centered underneath the abutting panels, you
can then nail them into place. There are also metal clips that you can use to
help fasten abutting roof sheathing panels together.
It is important that each adjacent row of roof sheathing be staggered so that
vertical seams do not line up directly over one another. To do this, simply cut
a sheet of plywood or OSB into two 4x4 sections. Start the second course of
roof sheathing panels with one of the 4x4 sections. Then continue to work
across the width of the roof with 4x8 panels. Alternate with full and half
sheets as you continue to work your way up the roof line.
Photo by Mark Donovan
When you near the far end of each course of roof sheathing you can either
immediately trim the board to the proper length, or hold off and trim all the
panels at once. Trimming all of the panels at once typically is the most
efficient way. Simply snap a chalk line from the eave to the ridge along the
outer edge, set your saw blade on your circular skill saw to the proper
thickness, and cut away the excess sheathing.
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Continue to work your way up towards the ridge by installing one course of
sheathing panels after another. Again alternate starting each new course with
full and half width panels to make sure adjacent panel vertical seams do not
line up directly over one another. When you near the roof ridge, rip saw plywood
/ OSB panels accordingly to complete the sheathing. However, leave about a 1
opening at the top of the ridge to allow for air to exit the roof. Ridge vent
will be installed over this gap to prevent water infiltration into the attic
To complete the roof sheathing, repeat the process on the remaining roof slopes.
For help on Shingling Your Home's Roof, see HomeAdditionPlus.coms
Asphalt Shingle Roofing Bid Sheet.
Asphalt Shingle Roofing Bid Sheet
help to ensure
your roof won't end up with a blue tarp over it and a dumpster sitting in your
yard for weeks
as you wait for the roofing contractor to come back and finish roofing your
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