Your asphalt roof may see plywood damage in the case of extreme weather, such as torrential rain and wind or unexpected snowfall. If shingles get ripped away, the plywood is then exposed to the elements and may need replacing. You may also have experienced a leak and realized that there's hidden damage. Follow these steps to inspect and replace your plywood.
Step 1: Separate Undamaged Shingles
This step will be unnecessary if the shingles on your roof have been blown away or already removed in some capacity. If they haven't, take your pry bar and gently loosen the shingles, starting with the row below the ones that have been damaged. Plywood is normally 8 feet long and broken up into smaller sections, so you will need to remove all the shingles in the area where new plywood will be placed.
You're not removing them, only separating them so you can remove the damaged shingles later. There will be cases where you can't exactly tell where the damage is, so you will have to work your way from the bottom. If you do know, just shift the layer underneath the damaged shingles and work in a circle.
Step 2: Remove Damaged Shingles
To remove the damaged shingles, hold the bottom left and right sides and pull downward, alternating directions. The movement should be going down toward you and going from left to right until you can pull out the shingle. Repeat this process until all damaged shingles have been removed.
Step 3: Pull Nails
After removing the damaged shingles, pull out the nails underneath. It's best to use a pry bar for this, as its flat surface will be less likely to damage any good shingles in the area than a hammer. If your roof is completely bare of shingles, you can use either tool.
Step 4: Remove Underlayment
Asphalt roofs are almost always laid over a felt underlayment, which is very easy to remove. A lot of times, simply removing the shingle will take off the felt, but if not, all you need to do is take out the nails and pull it off.
Step 5: Replace Plywood
Once you've determined how much plywood you will need, cut it to size. To remove the existing plywood, pull out the nails and gently tug it out of place. The new plywood should then be hammered into place.
Step 6: Apply Roofing Felt and Replace Shingles
Tack the roofing felt into place over the plywood with either a hammer or staple gun, and you're ready to replace the shingles. Make sure to use at least 6 nails for each shingle to get the best possible hold. Depending on the size of the replacement, you will need to place the shingles from the bottom up, and for a large area, work in a triangle shape from the bottom to the top.