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How Improper Ventilation Can Damage Your Roof

You may have heard that roofing shingles can be fried from the buildup of heat that occurs when insufficient ventilation is present. But practically every other part of your roof can be damaged by this problem as well. Here’s how.

1. Rafters and Sheathing

In addition to heat, excess condensation builds up in the attic when there’s not enough ventilation. This condensation can sometimes occur only at night, but if there’s a lot of moisture in the air, your roof’s underside could be wet all day long.

Your roof’s rafters and sheathing are both typically made of wood, making them vulnerable to water damage such as rot and fungus growth. The sheathing, also known as the roof deck, is often made of plywood. These types of sheathing are made up of many individual strands or sheets of wood, which can come apart when exposed to water.

Although rafters tend to be solid wood beams, they too can swell in the presence of condensation. Not only does this make the entire surface of your roof deck and rafters a great place for mold growth, but it also encourages certain types of termites called dampwood termites to infest your house. As the name implies, this type of termite seeks out water-damaged wood.

2. Insulation

Condensation doesn’t just collect on the underside of your roof and stay there. It can actually drip down all over the attic insulation, which causes a number of additional problems. First of all, the water fills in the air gaps inside the insulation, making it much better at conducting heat and much worse at insulating.

Secondly, depending on what type of insulation you have, this can create a haven for mold growth. Although fiberglass insulation is typically resistant to mold and mildew, the paper coating often wrapped around the insulation batts is organic material that mold will love.

3. Fasteners

The roofing nails used to hold your shingles on can suffer from moisture damage as well. These fasteners can become rusty when excess moisture is present. Some types of roofing nails are more vulnerable to this issue than others; for example, electro-plated roofing nails will likely rust faster than hot-dipped nails.

As you can imagine, having the nails that secure your shingles rust through is bad news. While you can’t easily change the type of fasteners used in your roof, you can keep the condensation to a minimum to prolong the life of these fasteners.

4. Underlayment

Excess moisture can cause roofing felt, also known as underlayment, to expand and wrinkle. This causes little ridges that are visible from the outside of your roof where the wrinkles push shingles up slightly. Unfortunately, you can’t fix this issue by drying out the underside of the roof; the wrinkles will simply dry in position and remain fixed in that shape.

This problem can occur either directly after re-roofing, if the roofers used roofing felt that had too much moisture in it or installed the roof during wet weather. But it can also occur when the felt absorbs water from beneath over a period of time because your attic is too moist.

As you can see, keeping your roof dry and well-ventilated is critical not just for longer shingle lifespans, but for the health of your underlayment, roof deck, rafters, roofing nails, and even insulation. Check for signs of poor roof ventilation, such as high attic temperatures, moisture on the underside of the roof, and high AC usage.

If you think your roof has a ventilation problem, you should have it looked at right away before serious damage can occur. Check our website to learn more about our services and call today if you’d like a free estimate from A&W Custom Carpentry and Roofing.

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