Water is your roof’s number one enemy. Since roof decking is made from wood and wood composites, it is especially prone to rotting and water damage when incessantly exposed to prolonged or excess moisture.
Ice dams are problematic because they cause water to pool and then it starts to flow back up the roof against the grain. Now the water leaks from the roof into the building envelope as well as the ceiling and walls. This will often lead to rotted roof decking, rafters as well as exterior and interior wall framing and sheathing rot.
As the water starts to dam up behind the ice ridge and because shingles are designed to repel water down a roof, water backing up can quickly get under the shingles and pour into the house. Water is very good at finding cracks and leaks to penetrate especially when it is just sitting there pooling.
Water will often leak down within the wall frame where it dampens wall insulation and causes it to drop off leaving uninsulated voids at the top of the wall. Energy dollars are again drained, but more significantly, moisture gets caught within the wall cavity between the exterior plywood sheathing and interior vapor barrier.
The result is stinking, unstable, rotting wall cavities. Structural framing supports can decay. Metal fasteners may corrode, losing integrity. Now your shingles need to be removed in the impacted areas and the rotted-out roof decking needs to be removed.
Rotted roof decking can’t be repaired. It must be fully replaced. The longer you let it remain, the more problems it can create, leading to costly repairs. While replacing a roof is an expensive undertaking, it’s less costly in the long run than also replacing stained drywall, waterlogged framing, and joists, or a water-damaged electrical system.
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