5 Decking Issues That Can Affect a Roof Overlay

A roof overlay is a special type of roof replacement where the old shingles are left in place and new ones are installed over the top. This is an excellent way to speed up roof installation and save money, but it isn't always the best option. Issues with the roof decking may mean that a complete teardown and full replacement are a better idea.

1. Sagging Roof Deck

Your roof planes should be straight, with no sagging along the main surface of the roof. There should also be no sagging along the ridgeline, which must be strong and level. Sagging indicates underlying damage or rot to the decking boards, which will necessitate the removal of the old decking and installation of new. 

2. Spongy Surface

Your roofer will walk the entire surface of the roof. They are checking for sponginess, where the roof seems to sink or feel springy beneath their feet. Roof decking in good condition will be firm and won't move. Spongy decking means moisture has seeped into the decking and caused water damage. Rot is often present, which will eventually cause the decking to fail if it is not replaced. 

3. Popped Nails

One or two popped nails may not be a huge issue on an older roof, as simple temperature fluctuations and drying out can cause a nail to pop. An extensive amount of popped nails, particularly over a small area, indicates that water has infiltrated the decking and caused it to swell. The swelling wood fibers push out the nails, or the nails may pop when the wood dries. Wood rot will soon follow if it isn't already present. 

4. Internal Water Damage

A good roofer will inspect your attic before recommending a roof overlay. They are looking for signs of leaks. These can include water spots on the ceiling, which is the underside of the decking, as well as mildew and mold. If any symptoms of a roof leak are found in the attic, then a full replacement is a better idea than an overlay, as the decking may need to be replaced or repaired before the new roof is put on.

5. Loose Flashing

The flashing around chimneys, vent stacks, and other roof top penetrations is there to guard against water leaks at the seam between the item and the shingles. If your roofer finds loose or missing flashing, there is a good chance that water has made its way under the shingles and caused damage to the decking beneath.

Contact a roof replacement contractor in your area if you need help assessing your roof.