15December 2025
Every homeowner wants to save money on a roof replacement. When you see the estimate for a full tear-off, it is tempting to ask, “Can’t we just slap new shingles on top of the old ones?”
The short answer is: Yes, it is often legal in New Jersey. But just because you can doesn’t mean you should.
While an “overlay” (or reroofing) saves money upfront, it often costs double in the long run. As your local GAF-certified experts, T.A. Hughes III Roofing wants to explain why you should be careful if you plan to install a new roof over an old one in South Jersey.
The “Two-Layer” Law in New Jersey
Most building codes in NJ municipalities—from Cherry Hill to Washington Township—allow a maximum of two layers of roofing material on a home.
This means if your home already has two layers of shingles (which is common in older historic towns like Collingswood or Haddonfield), you must do a full tear-off. It is illegal and unsafe to add a third layer.
Quick Check: Go to the edge of your roof and look at the shingles from the side. If you see two distinct stacks of shingles, an overlay is not an option for you.
Why South Jersey Weather Makes Overlays Risky
Our climate is unique. We have intense summer heat and heavy winter snow. Here is why that matters for a two-layer roof:
- The Heat Trap: Asphalt shingles absorb heat. When you have two layers, the heat gets trapped between them. This “bakes” the new shingles from the bottom up, causing them to curl and crack years earlier than they should.
- The Snow Load: Winter storms in Burlington County can dump heavy, wet snow on your home. Two layers of shingles plus wet snow adds immense weight to your rafters, which can cause sagging in older homes.
- Hiding Algae: If your old roof has moss or algae (common in wooded areas), putting new shingles on top is like putting a bandage on a dirty wound. The fungus can continue to rot the wood underneath.
The 3 Hidden Dangers of Reroofing
Before you sign a contract for an overlay, consider these three risks:
1. You Can’t Fix What You Can’t See (Decking)
The most important part of your roof isn’t the shingle; it’s the wood deck underneath. If you do an overlay, we cannot inspect the plywood for rot or water damage. You might be nailing a brand new roof into rotten wood.
Learn more about why this layer matters in our guide: What’s Under Your Shingles?
2. It Kills Your Warranty
Top manufacturers like GAF offer their best warranties only on roofs that are installed on a clean deck. Because an overlay surface is lumpy, the new shingles won’t seal perfectly flat. This often reduces or voids the wind warranty coverage.
Read more: Roofing Warranties Explained
3. Future Resale Value
If you plan to sell your home, be careful. Home inspectors check specifically for multiple roof layers. A roof with two layers is a major “red flag” for buyers and can lower your home’s resale value.
Cost Comparison: Tear-Off vs. Overlay
The Overlay (Cheaper Now):
You save money upfront because there is less labor (no tearing off old shingles) and lower disposal fees (less trash to haul away).
The Tear-Off (Cheaper Later):
It costs more today, but it ensures your roof lasts 20–30 years. Plus, when an overlay eventually fails, you have to pay to remove two layers of shingles. This effectively doubles your labor costs in the future.
When Does an Overlay Make Sense?
We don’t want to say “never.” An overlay might be a valid option if:
- Your roof has only one layer currently.
- The roof deck is solid with zero spongy spots or leaks.
- Budget is your absolute top priority and you understand the roof lifespan will be shorter.
However, for most Camden and Gloucester County homeowners, a tear-off is the only way to guarantee a leak-free home.
Frequently Asked Questions
Q: How much money do you save by putting a roof over an old one?
A: You typically save about 20–25% upfront on labor and disposal, but you likely lose about 40% of the roof’s potential lifespan due to heat trapping.
Q: Does a second layer of shingles add insulation?
A: Minimally, but not in a good way. It mostly traps heat between the layers, which cooks the shingles and can actually make your attic hotter.
Q: How do I know if I have bad decking under my shingles?
A: Spongy spots when walking on the roof, sagging sections, or nails popping up are key signs. A professional inspection is the safest way to know for sure.
Get Honest Advice on Your Roof
Don’t cut corners on your home’s protection. A fresh start with a tear-off ensures your roof lasts for decades. Not sure how many layers you currently have?