3 Common Problems In Winter Leading To Roof Damage

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Winter brings a new set of potential problems for a roof. While we’ve discussed a few of these in in an earlier article on protecting your roof from snow damage, we’ll dig a bit deeper here.

1) Snow accumulation

Our location in the Pacific Northwest generally means less snow that other parts of the country. We’re less concerned about the weight or accumulation of snow, though it can be a concern, especially if you have a flat roof. 

There is little to nothing you can do to prevent snow accumulation. The biggest concern with accumulation is the weight and your best ‘defense’ is to make sure your roof can handle it. We’re not talking about testing the roof to see how much it can support. It’s about making sure any weak posts in the roof decking are identified and repaired BEFORE there is additional weight on it, testing its limits.

With heavy, wet snowfalls being less common here, our primary focus is water infiltration and damage to the roof itself.

2) Water infiltration

Small leaks can become larger ones in the winter. While rain will run off and drain away, snow stays put until it melts. Once it does, the run-off is slow. This allows more time for water to find a hole and work its way into it. While water getting in is a serious problem, the potential for that water to freeze the real problem. Water expands when it freezes. Over time, especially if the wood decking or rafters have already been damaged by moisture intrusion, the freezing will further damage the substructure to a point of allowing more water inside. 

Freezing water can just as easily damage roofing shingles by getting into small cracks.

Wind. While not restricted to winter, the Pacific Northwest gets more, and stronger winds in the winter months. Winds have a way of driving water into places it may not otherwise reach – being blown up a roof or pushed into normally sheltered crevices or under shingles and flashing if anything is loose. 

Wind can have the same effect as snow. It can drive rain against or into the roof, eaves, and valleys slowing the run-off. Compounding this, it can force water into existing holes – more than can be absorbed into the wood and later dry out. Wind has a way of ‘creating leaks’ a homeowner never knew existed, or make ones known, worse.  

Ice build-up. Potentially worse than snow accumulation is ice accumulation. With wind and temperatures which can hover at or slightly above freezing all day and trees preventing any sun from warming the roof surface, water freezing on a flat or low-pitched roof is possible. 

Even without cracks in shingles, flashing, or chimneys, damage as water freezes and expands is possible. Asphalt shingles are very susceptible. Water can freeze under them and between the tabs causing the to lift or crack. Long-term, freezing makes them more brittle and at risk for damage from wind and damage from contact (tree branches falling and walking on them). 

Water getting in isn’t the only concern. Water being trapped is as well.

3) Condensation 

Condensation is the change of water from its gaseous form (water vapor) into liquid water. It generally occurs in the atmosphere when warm air rises, cools and looses its capacity to hold water vapor. ~ Department of Atmospheric Sciences (DAS) at the University of Illinois at Urbana-Champaign.

Warm air inside our homes (thanks to turning on the heat to keep warm) rises. As it does, it will come in contact with the roof line. If allowed to get trapped against the roof (inside an attic), the roof, being much cooler will cause the warm air to condense. The result is trapped moisture which can lead to rot and mold. 

While not directly a roof issue, condensation can result in damage to the joists and decking creating long-term problems and expensive repairs.


Be prepared

We cannot prevent weather, snow, rain, wind, and temperatures, from affecting our roofs. We can, however, take measures to limit the damage they create by being preemptive.

Routine maintenance. Most issues from water filtration come from existing damage. Winter, cold, snow, and ice, can create new problems but are more likely to make existing ones worse. Routine maintenance and repairs done promptly are the best method for limiting the havoc winter can do to your roof.

Insulation, ventilation and air barriers. 

  • Insulation will help reduce warm air from contacting cold surfaces reducing the risk of condensation 
  • Ventilation is critical as moisture is also present in the air. Moisture diffusion is possible – moisture moving from one space to another, or into and out of a substrate (your walls, roof decking) – without airflow. However, without air the rate at which it occurs rather slow. Air transported moisture is far more substantial and important source of moisture movement. 

    Proper ventilation will help remove excess moisture preventing it from being trapped where damage can occur.

  • Air barriers, as the name implies, are designed to prevent air from moving between spaces. With no air movement, the risk of moisture moving is significantly reduced. Properly located and installed air barriers will minimize moisture damage. The use of vapor barriers, especially permeable ones, allow moisture which does work it’s way in a path to escape. 

    A roof leak will allow water into the decking. A good vapor permeable membrane will allow that moisture to move into the attic, where, if there is proper ventilation, it can be removed from the space. Without the vapor permeable membrane and proper ventilation, the moisture would be trapped against the roof resulting in long-term damage and expensive repairs.

Winter creates several unique concerns for our roofs and living spaces.

We cannot prevent the forces of nature from reaching us, but we can limit the impact on our roofs and homes with a few preemptive measures.

This starts with inspections and maintenance


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