Puddling water is often considered a problem that only affect flat roofs, but even sloped roofs can suffer from water collection. If you notice puddles on a sloped shingle roof, you can be relatively sure that there is something else wrong with the roof that is causing the problem.

1. Decking Damage

The decking is the plywood sheathing that makes up the main surface of the roof to which the shingles are then attached. If moisture damages the decking, it can swell and warp, which then results in an uneven roof surface that could hold puddles of water. Warped decking must be replaced, as water damage on wood cannot be effectively reversed.

2. Aging Shingles

Cupping is an issue that affects older shingles that are beginning to fail. The name comes from the cupped shape that develops as the edges of the shingles begin to curl up. Once this occurs, each cupped shingle can hold a puddle of water, which will drain off slowly on even the steepest of roof pitches. Replacing the roofing shingles is the best repair option, as cupping indicates that all of the shingles are reaching the end of their working lifespan.

3. Bowed Supports

Every pitched roof features at least one ridgeline, although hipped roofs and those with complicated designs my have several ridgelines. There are also additional ceiling joists that help support the roof decking and the roof itself. If these ridgelines and joists suffer damage or become warped, they can bow and cause sections of the roof plane to dip lower so that puddles collect. Replacing the supports is required.

4. Weight Stress

Too much weight on a roof can cause parts of it to bow, thus leading to puddling when the water can't drain properly. Weight can be a result of snow and ice that has accumulated on the roof, or it may be from debris from fallen branches or moss growth. Cleaning off the roof may fix the problem, but the underlying structure should be assessed by a roofer to ensure there is no permanent damages.

5. Shingle Obstructions

Obstructions can get beneath the shingles, lifting them up so that a little dam is created that can cause puddling. Ice dams are common in winter, particularly on poorly insulated and ventilated roofs. Moss can also grow beneath a shingle and lift it to form a dam, which can be repaired by having the moss cleaned from the roof and anti-moss zinc strips added to the shingles.

Contact a roofing repair service if you notice water puddling on your sloped shingle roof.