How to Replace Roof Sheathing

What You'll Need
Pry bar with flat end
Work gloves
Safety goggles
4-foot pry bar
Reciprocating saw
Circular saw
Measuring tape
Chalk line
3/4 -inch exterior plywood
Galvanized roofing nails
Scaffolding or extension ladders
Building paper

Roof sheathing is typically made from plywood and is attached to the top edge of roof trusses as well as rafters. They tie the roof together, but they also help to support the roof materials. Over time, roof sheathing can be damaged and need to replaced. Damage can occur from excess water as well as bad storms. You can install roof sheathing yourself, but the project is difficult. Follow the steps below to complete this project on your own.

Step 1 – Marking the Work Area

Determine which section of roof sheathing to remove, and build your scaffolding to that area. If your home is one story, use extension ladders instead. When you and your assistant are on the roof, move to the end of the area to remove. Give your assistant one end of the chalk line and have him walk to the other edge of the area to remove. Snap the chalk line to mark off one section of the perimeter of the roof sheathing to remove. Repeat this 3 more times for each area to create a rectangular section to remove.

Step 2 – Accessing the Roof Sheathing

To uncover the roof sheathing, you need to remove the shingles. Use the flat pry bar to do this by running the flat end under the shingles and leveraging them up. Take away all of the shingles along with the wrap underneath until you uncover the plywood. Take the time to also remove any roofing nails that may still be in the wood.

Step 3 – Remove the Roof Sheathing

The roof sheathing needs to be cut in order to be removed. Put on your safety goggles and work gloves as you will be using the reciprocating saw. Use the saw to cut along the perimeter from which you removed the shingles and wrap. Remove the wood from the roof, using the longer pry bar to assist you. When you are done, the rafters of the home will be exposed. Toss the waste material to the side.

Step 4 – The New Roof Sheathing

The roof sheathing you are replacing needs to be sized to fit the open area. Use the tape measure to measure the area for the new roof sheathing. Transfer these measurements to the ¾-inch exterior plywood. Place the plywood on the sawhorses, and then cut it to the measurements. 

Put the new roof sheathing in place, making sure it fits snugly and rests on the rafters. Nail it in place by putting one nail every 6 inches, making sure the head of the nail is flush with the wood. Apply new roofing wrap, trimming it and then nailing it down. Install new shingles that match the old ones. Place the new shingles under the old ones to overlap them, and then nail in place. Continue in this manner under new shingles are installed.