If the sheathing is properly gapped then the gaps can close causing the shingles spanning the gap to buckle.
Moving roofing shingles up to roof.
Replace the area where the shingle was removed with another shingle of similar weight and color.
Your roof is what keeps you protected.
Both step shingling and racking will yield a watertight roof.
When plywood or osb sheathing picks up moisture it expands.
After completing a column the roofer can go back down to the eave edge of the roof and start laying the next column of shingles.
Take your utility knife or a putty knife and gently push it underneath the shingle to pry it free.
The shingles will roll up like a ball in front of the fork.
Remove shingles in a 2 to 3 ft wide section as you work down the roof.
Should you decide to go with the old roof and do end up removing any of the old shingles make sure that you apply a layer of 30 pound roofing felt before you begin laying any new shingles.
How to get shingles on your roof easily.
Push the shingles down to the roof jacks.
To move a roof shingle use a claw hammer to remove the roof nails.
This saves a lot of time moving shingle bundles and a lot of back strain.
Pull the shingle from its place and move it to the side.
The most common cause appears to be movement in the roof sheathing with changes in moisture levels.
In cases where the damage is extensive removing the old roofing shingles completely is advisable.
Continue tearing off the shingles and underlayment until you reach the roof jacks then start over at the top of the roof.
Not only that the shingles can be piled just to the side of the column being laid.
It provides you with peace of mind knowing that you and your family are safe from rain snow hail wind heat and cold.