Can You Roof Over Existing Shingles?
Are you thinking about reroofing your home? You might wonder if you can install new shingles over existing ones. It’s a common question with a complex answer. Roofing over existing shingles is tempting if you want to save money and time. However, before you start this roofing project, there’s a lot to know.
I’ve worked in roofing for over 20 years and have seen good and bad reroofing jobs. It’s more complicated than installing shingles on top of old ones. There are more factors to consider when redoing your shingle roof.
Let’s discuss why you might consider a roof over existing shingles. People mainly do it to cut costs. Removing an old roof requires a lot of work, increasing roof replacement costs. You also must deal with the waste. Reroofing might seem like a good shortcut, but there are better choices.
In many cases, it creates more problems later. I’ve seen people who thought they were saving money, but it ended up costing them more because of reroofing issues. So, what should you know before you install a roof over existing shingles? Let’s find out.
Is Reroofing Right for You?
Before assuming reroofing is a good idea, determine if it’s possible. Consider a few key factors:
The Condition of Your Existing Shingle Roof
Your current roof must be in good condition for reroofing to be possible. If you have curling shingles, cracked shingles, or missing shingles, a complete replacement is better.
Number of Existing Layers
Most building codes only allow for two layers of roofing. If you already have two, you’ll need to remove everything before adding another roof. This is for safety, as too many layers add too much weight to your roof structure.
Roofing Materials
You can only roof over existing shingles if you currently have asphalt shingles. For other materials like wood tiles or slate, you’ll need to remove the old layer before installing shingles.
Pros and Cons of Installing Shingles Over Existing Shingles
If you’ve determined that reroofing is an option, it’s time to weigh the benefits and drawbacks.
Pros Cons
Lower initial cost Shorter lifespan of new roof
Faster installation Can’t inspect or repair the deck
Less mess and waste May void manufacturer warranties
Added insulation Potential for trapping moisture
The Cost of Roofing Over Existing Shingles
Let’s discuss finances, as that’s usually why homeowners consider reroofing. Installing new shingles over old ones can usually save about 25% on labor costs. That’s significant.
But while you might save upfront, you could spend more overall. A roof over existing shingles usually lasts less time than a brand new roof. You might save $2,000 now, but is it worth it if you must replace your roof in 15 years instead of 25?
The Time Needed to Install Roof Over Existing Shingles
Reroofing is faster than removing and replacing your existing roof. A typical home might require one or two days for reroofing versus three to five days for a complete replacement. This could be important if you’re short on time.
But faster isn’t always better. Rushing the job leads to mistakes, which can be costly when it comes to your roof. It’s better to spend more time and ensure the job is done correctly and appropriately for your specific roof than to rush it and have problems later on.
The Process of Installing a Roof Over Existing Shingles
If you choose reroofing, here’s what to expect:
- Inspection: Your roofer will thoroughly inspect your current roof to look for soft spots, leaks, or other damage that needs to be addressed.
- Preparation: They’ll repair or replace damaged shingles to create a smooth roof surface.
- Installation of Underlayment: The roofers will install a layer of underlayment over your existing shingles to prevent moisture.
- Installing Shingles: Next, they install the new shingles over the old ones, using long nails to penetrate through to the roof deck.
- Flashing and Ventilation: The roofers will install flashing around chimneys, vents, and other roof penetrations. They also need to ensure adequate ventilation to prevent moisture buildup.
It seems simple, but a lot can go wrong if it’s not done right. That’s why hiring experienced and professional roofers is critical if you choose reroofing.
Potential Problems with Roofing Over Existing Shingles
Reroofing has many potential problems, and these are some of the most common ones I’ve encountered:
Trapped Moisture
This is the biggest concern. Moisture trapped between the old and new shingle layers leads to rot, mold, and leaks. I once saw a home where the owners had reroofed about five years earlier.
When I removed both layers, the plywood decking was rotten because of moisture. The homeowners needed their entire roof structure replaced.
Weight of Shingles
An extra layer of shingles is heavy. While most homes can handle the weight, it’s risky, especially in areas with heavy snowfall or severe thunderstorms.
Uneven Surface
Over time, your original shingles develop dips and bumps. When new shingles are installed over them, the imperfections show through, affecting how the new roof looks and performs.
Shorter Lifespan
A roof over existing shingles usually doesn’t last as long as a new roof installed on a clean deck. This is because the heat trapped between the layers makes the new shingles deteriorate faster. You’ll need to replace your roof sooner, which is another cost to factor in.
When to Avoid Reroofing
While reroofing is a good idea in some instances, you shouldn’t do it in other situations like:
- Your current roof has significant damage or leaks.
- The roof deck is sagging or rotting.
- You live somewhere with high winds or hurricanes.
- Your home already has two layers of roofing.
- You plan on staying in your home long-term.
A complete tear-off and replacement is the better choice in these cases, even though it’s more expensive. It allows for inspection and repair of the roof deck, proper installation, and a longer-lasting, better-performing roof.
FAQs About Installing Shingles Over an Existing Roof
Is it a good idea to install new shingles over old ones?
It depends on your existing roof’s condition, local building codes, and your plans. Consult a professional roofer before making a decision.
Is it cheaper to put new shingles over old ones?
Yes, initially. Doing this saves you about 25% on labor costs compared to removing the old shingles. However, you’ll likely pay more long-term due to potential issues and the shorter lifespan.
How do you reshingle a roof over existing shingles?
A roofer will inspect and prepare the existing roof, install the underlayment, and then lay the new shingles. It’s best to hire professionals to ensure it’s done correctly.
Can you install a roll roof over existing shingles?
Installing roll roofing over existing shingles is possible, but it’s not ideal. Roll roofing is better for low-slope or flat roofs and won’t protect well when installed over existing shingles on a standard-pitched roof.
Conclusion
Take your time deciding whether to roof over existing shingles. While it might save money in the short term, it’s not always the best long-term solution for your home. A full tear-off and replacement is better, though more expensive upfront. It allows you to inspect the roof deck and ensures proper installation, creating a longer-lasting, better-performing roof. But every situation is different.
If your current roof is in good condition, you’re on a budget, and you plan to move soon, reroofing might be a good idea. The key is to hire a trustworthy roofing contractor to assess the situation and offer honest advice. Get several opinions before deciding.
Your roof protects your home from the elements. Whether you roof over existing shingles or get a new roof, make an informed choice to protect your home for years to come.
