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Shingles Over Shingles: Should You Install a New Roof Over the Old One?
When the time comes to replace a roof, many homeowners are surprised to learn that they might have another option besides a complete tear-off. That option is installing shingles over shingles, a process known as a roof overlay. Instead of removing the old shingles and starting from scratch, this method involves placing a second layer of shingles directly over the existing ones.
This might sound like an easy solution—and in some cases, it is—but installing a second layer of shingles is not always the best choice. There are advantages, drawbacks, safety considerations, building code issues, and long-term implications that every homeowner should understand before deciding to move forward with this approach.
This comprehensive guide explores everything you need to know about putting shingles over shingles. Whether you’re looking to save time and money or just wondering what the pros and cons are, this guide will give you a complete picture of what’s involved.
Table of Contents
- What Does “Shingles Over Shingles” Mean?
- Why Do Homeowners Consider This Option?
- Pros of Installing Shingles Over Shingles
- Cons and Risks of Overlaying Shingles
- Structural Considerations Before Starting
- Building Codes and Legal Restrictions
- Roofing Warranties and Manufacturer Guidelines
- How Overlaying Affects Ventilation and Insulation
- Roofing Materials That Work (or Don’t Work) With Overlays
- Step-by-Step Overview of a Typical Overlay Installation
- Visual and Curb Appeal Factors
- Real Cost Comparison: Overlay vs Tear-Off
- Environmental Impact of Both Options
- How to Decide What’s Right for Your Roof
- When a Full Tear-Off is Non-Negotiable
- FAQs About Shingles Over Shingles
- Final Thoughts
1. What Does “Shingles Over Shingles” Mean?
The phrase “shingles over shingles” refers to the process of installing a second layer of asphalt shingles directly on top of the existing layer. This practice is legal in many areas and has been around for decades. It’s generally used as a cost-saving or time-saving alternative to a full tear-off, where all the old shingles and underlayment are removed before new roofing materials are applied.
Overlaying is typically only done with asphalt shingles, the most common roofing material in North America. Metal, wood, or tile roofs are not suited for this method. In fact, even some types of asphalt shingles or older materials can complicate an overlay job.
2. Why Do Homeowners Consider This Option?
There are a few reasons homeowners and even some roofing contractors propose the shingles-over-shingles method:
- Cost Savings: Labor and disposal costs for tearing off old shingles can be significant. Skipping that step can reduce total project costs.
- Speed: An overlay can be completed more quickly, with fewer steps involved.
- Less Mess: Without demolition, there’s less debris, noise, and disruption around the property.
- Temporary Fix: For those planning to sell their home soon, an overlay can offer a fast cosmetic improvement without a huge investment.
While these reasons are appealing, they don’t tell the whole story. For some homes, overlays make sense. For others, they can create bigger problems down the line.
3. Pros of Installing Shingles Over Shingles
Let’s start with the potential benefits of this method. Under the right conditions, it can be a practical approach.
1. Lower Costs
Avoiding a tear-off eliminates the labor required to remove old shingles and dispose of them. This can save $1,000 to $2,500 or more, depending on roof size and local labor rates.
2. Quicker Installation
Roofing crews can complete the job faster since they don’t have to remove the old materials or prepare the roof deck from scratch.
3. Less Waste
Shingles aren’t going into landfills if they’re left in place. Environmentally-conscious homeowners may see this as a small advantage.
4. Less Intrusive
No tear-off means less noise, fewer nails, less debris, and shorter job duration. For families living in the home during the project, that’s a real bonus.
4. Cons and Risks of Overlaying Shingles
While the benefits may sound appealing, the drawbacks are important—and potentially more costly in the long run.
1. Can Hide Existing Damage
An overlay does nothing to address problems like:
- Leaking flashing
- Rotting or soft roof decking
- Mold or mildew under the shingles
If issues exist beneath the surface, they’re simply buried, not fixed.
2. Added Weight
A new layer of shingles adds significant weight—about 2.5 to 3 pounds per square foot. For a 2,000-square-foot roof, that’s an extra 5,000 to 6,000 pounds your structure needs to support. Older homes may not be designed for this.
3. Reduced Lifespan
Overlay roofs typically don’t last as long. Because heat gets trapped between the layers, shingles may deteriorate faster. Lifespan reductions of 20–30% are not uncommon.
4. Void Manufacturer Warranties
Most asphalt shingle manufacturers do not warranty shingles installed over existing layers. If you overlay and something goes wrong, you’re on your own.
5. Poor Aesthetics
An overlay may not lay flat, especially if the old shingles are curled or uneven. This can create a bumpy or wavy appearance that detracts from your home’s curb appeal.
5. Structural Considerations Before Starting
Before adding a second layer, your roof should be evaluated by a professional. Important structural concerns include:
- Decking integrity: Must be solid, with no rot or soft spots.
- Load-bearing capacity: Must support additional weight.
- Ventilation system: Must be capable of venting a roof with added insulation and shingle layers.
If your roof has already had an overlay in the past (i.e., it’s a second overlay), most local codes will prohibit a third layer.
6. Building Codes and Legal Restrictions
Most local building codes allow one re-roof (overlay), but not more than two total layers of shingles. Any roof with three layers is typically deemed out of compliance and must be fully torn off before re-roofing.
Permits are usually required for a roofing job, even an overlay. Be sure to check with your local building departmentbefore proceeding.
7. Roofing Warranties and Manufacturer Guidelines
As mentioned earlier, many shingle manufacturers clearly state in their warranty documentation that installing new shingles over existing ones may void the warranty. That means if the product fails—whether due to heat damage, curling, or adhesion problems—you won’t be covered.
If you choose to overlay, verify what your product warranty covers. You may need to sign a waiver or accept reduced protection.
8. How Overlaying Affects Ventilation and Insulation
Trapping an additional layer of shingles over the old ones can create heat retention issues. Your roof gets hotter in the summer, and that extra heat can lead to:
- Accelerated aging of shingles
- Increased energy bills
- Higher attic temperatures
- More strain on HVAC systems
Also, inadequate ventilation increases the risk of condensation, which can rot your roof deck over time.
9. Roofing Materials That Work With Overlays
Overlaying is only suitable with certain materials.
Suitable:
- Asphalt shingles over asphalt shingles (in decent condition)
Not Suitable:
- Metal over shingles (requires specific framing)
- Wood shake (too uneven)
- Tile or slate (too heavy and brittle)
Even within asphalt shingles, the condition of the old layer matters. If the original shingles are:
- Curled
- Brittle
- Missing in spots
…then overlaying is not recommended.
10. Step-by-Step Overview of a Typical Overlay Installation
Here’s how the process usually goes:
- Inspection of existing roof
- Removal of ridge caps and vents
- Installation of underlayment (optional but recommended)
- Nailing new shingles over the existing ones, offsetting seams
- Reinstallation of ridge caps, flashing, and vents
- Final inspection
Overlay jobs may skip steps like replacing flashing or reworking vent systems, which is part of why they’re cheaper—but also riskier.
11. Visual and Curb Appeal Factors
While some overlay jobs look acceptable, others clearly show imperfections:
- Uneven lines
- Bumps where old shingles are damaged
- Wrinkled ridge lines
- Visible dips in decking
All of these can reduce home value and make it harder to sell your property in the future.
12. Real Cost Comparison: Overlay vs Tear-Off
Let’s compare cost on a 2,000-square-foot roof 440-235-3124
