Is it a good idea to add a second layer of shingles?
Your roof isn’t looking so good, and you may be tempted to add a second layer of shingles. It sounds easier than a full roof replacment, but read on to discover why that may not be a great idea.
4 Potential Problems From Installing Shingles Over Shingles
Adding a second layer of shingles to an existing roof is not a good idea. While it can be less expensive than removing and replacing the roof, adding roofing layers can create more problems later, resulting in other types of damage and premature roof failure. Some reasons why we do not advise adding layers of shingles are:
- Weight. Shingles are a heavy, durable roofing material that the rafters and sheathing of your home must support. Many homes are designed with a specific roof weight load, and exceeding it with a second layer of shingles can put significant pressure on your home’s framing.
- Mold Growth. Layering shingles over shingles creates a heat-and-damp-trap underneath the top (new) layer of roofing. This can cause deterioration of the roof’s substrate and cause problems with the wood roof decking. Algae and mold can also spread out onto the top layer and cause damage to the entire roof system, shortening the lifespan of the roof significantly.
- Hidden Leaks. An extra layer of shingles does not create extra waterproofing. The ultimate waterproofer on your roof is the underlayment (aka felt). If additional felt is not added, the roof is still prone to leak. When it does, finding the source of the leak may be impossible due to multiple roof layers being present.
- Appearance. Roofs with layers of shingles are commonly stricken with waviness in the shingle lines, which is an unappealing side effect of adding layers. Shingles are designed to be installed over a firm, flat nailable surface.
The Pros and Cons of Adding a Second Layer of Shingles
When it comes to roofing, there are a lot of different factors to consider. One major decision is whether or not to add a second layer of shingles.
This option has pros and cons, depending on the individual situation. Some property owners choose to add a second layer of shingles to save money on the overall roofing project. However, this can be more costly in the long run, as the additional weight can stress the underlying structure and lead to premature leaks. In addition, it can be difficult to match the new shingles exactly to the existing ones, leading to an uneven appearance.
There are some situations where adding a second layer of shingles makes sense. For example, if the original roof was installed incorrectly or is otherwise in poor condition, a second layer can help to correct these problems. In addition, if the property owner wants to make a major change to the roof’s look (such as switching from asphalt shingles to tile), the second layer of shingles can provide a smooth surface for the new material.
Ultimately, whether or not to add a second layer of shingles is a decision that should be made on a case-by-case basis. Property owners should consult a qualified roofing contractor to determine the best option for their situation.
Additional Shingles Will Harm the Roof
When it comes to protecting your home from the elements, your roof is your first line of defense. That’s why it’s important to make sure your roof is in good condition, and that includes having the right number of layers of shingles. While it may seem like adding a second layer of shingles would provide extra protection, in reality, it can actually do more harm than good.
The additional weight of the shingles can stress the underlying structure of the roof, and the nails used to secure the shingles can loosen over time and cause the shingles to become detached. In addition, shingles are designed to shed water, so if they are installed over an existing layer of shingles, they will trap moisture against the roof and cause premature deterioration.
For these reasons, most roofers recommend against adding a second layer of shingles. When it’s time to replace your roof, it’s best to start from scratch with a new layer of shingles.
It Can Decrease the Home Value and Shorten the Roof’s Life Span
Adding a second layer of shingles is never a good idea. On top of the visual imperfections it creates, which can decrease home value, it can shorten the lifespan of your roof. That’s the last thing you want. Shingles aren’t designed to have anything on top of them, let alone an entire layer of shingles, so they’ll degrade quickly.
Heat and moisture will get trapped between the layers, which will damage them and also cause the inside of your house to get hotter during the summer and more prone to leaking during the winter/wet months.
It Will Add Additional Costs With No Benefit
Adding a second layer of shingles is not a good idea, and I would not recommend it at all. Adding another layer traps more heat, thus affecting the whole temperature of the house, making it hotter than a single layer. Also, when there is more heat trapped in the roof, it can potentially damage the shingles sooner than later. This means you need to change them, and it is an additional cost. Finally, there is no benefit in adding another layer of shingle on, and you will only be causing problems on your roof.
This is a crowdsourced article. Contributors' statements do not necessarily reflect the opinion of this website, other people, businesses, or other contributors.