Roof Replacement Guide
Can You Put a New Roof Over Old Shingles in New Jersey?
Sometimes, but not if the roof already has two layers. New Jersey's residential building code does not allow a new covering over a roof that already has two or more layers, over slate or tile, or over a roof that is water soaked or too deteriorated to serve as a base. Even where a second layer is allowed, a full tear-off is usually the better job.
Roofing over existing shingles is called a roof recover, or an overlay. It skips the tear-off, which is why it comes up when people get a replacement estimate. Whether it's legal on your house is a code question with a clear answer, and whether it's a good idea depends on what is under the shingles you can see.
What the New Jersey code says about roofing over old shingles
New Jersey uses the International Residential Code, New Jersey edition, as the one- and two-family dwelling subcode of its Uniform Construction Code. Section R908.3.1.1 lists when a roof recover is not allowed. You cannot add a new covering when:
- the existing roof or covering is water soaked, or has deteriorated to the point that it is not an adequate base for more roofing
- the existing covering is slate, clay, cement or asbestos-cement tile
- the existing roof already has two or more applications of any type of roof covering
Plenty of older North Jersey houses were already roofed over once, and on those a third layer is out. The old layers come off. The town building department enforces this through the permit, so it isn't something a contractor gets to waive.
How to tell if your roof already has two layers
From the ground it's often hard to say. Look at the edge along the gutters and the rakes: a thick, stacked edge, or shingle tabs that look lumpy across the whole roof, can mean there's a layer underneath. A roof that looks wavy, or shows an older shingle shape peeking out at the edges, is another hint.
An inspection settles it. A roofer can check the layer count at an edge or a vent without damaging anything, and it should be written down. When you compare estimates, look for the number of layers each one plans to remove, because two quotes built on different layer counts are pricing different work.
Two-family homes deserve a second look. Where two owners share a ridge, each half may have been roofed at a different time by a different contractor, and the count can differ side to side.
Why a full tear-off is often the better choice anyway
Even when the code would allow a second layer, there are good reasons to take the old roof off first.
The big one is the deck. Rot and soft plywood hide under shingles, and a recover just covers them again along with whatever caused them. A tear-off exposes the deck so bad sheets get replaced before the new roof goes on. One customer, Jamil Frans, put it this way in a Google review: "During the tear-off, they discovered that the foundation of my roof was damaged and needed to be fully replaced, not just the shingles."
Flashing and underlayment get redone too. Leaks tend to start at chimneys, walls, valleys and vents, and laying new shingles over old flashing carries those weak points forward. With the roof stripped, the crew installs new underlayment, ice and water shield and flashing as one system.
New shingles also follow the shape of what's under them, so over curled or cupped shingles the surface stays uneven.
And warranties. Shingle manufacturers publish their own installation requirements, and some warranty options depend on how the roof went on. Ask which written warranty applies to the system being proposed.
Our own roof replacement work is a full tear-off, not an overlay. We take off the old covering, inspect the deck and replace soft sheets at a per-sheet price you agree to in advance.
Does removing extra layers change the estimate?
It can. Each layer adds labor and disposal, so two layers to remove is more work than one, which is why you want the layer count before you compare numbers. Roof size, pitch, deck repairs and the material you pick all shape the estimate as well. Our roof replacement cost page goes through those factors.
Questions to ask before you sign
- How many layers are on the roof now, and how did you check?
- Is this a full tear-off down to the deck?
- If you find bad decking, how do you document it and how is it priced?
- Which flashing, underlayment and ventilation items are in the scope?
- Who pulls the permit and schedules the inspection?
- Which written warranty covers the installed roof?
Not sure the roof needs replacing at all? Start with a roof inspection, or read our guide on whether to repair or replace your roof.
Four Seasons Roofing and Construction replaces roofs in Clifton and nearby North Jersey towns. We file the permit and schedule around the town inspection, and you get a written, itemized estimate after we've been up on the roof and photographed it.