Harrisburg PA RoofingDauphin & Cumberland counties

Homeowner question · Updated 2026-10-11

Tear off the old roof or shingle over it?

Pennsylvania's building code allows a second layer of asphalt shingles in some cases. Whether it is a good idea on your house depends on what is under the old roof, and that is hard to see without taking it off.

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What the code allows

Pennsylvania's Uniform Construction Code uses the International Residential Code for houses. Its re-roofing section lets a new layer of asphalt shingles go over an old one, but it requires the old roofing to come off first in several situations.

  • The roof already has two or more layers.
  • The existing roofing is water-soaked or has deteriorated so it can no longer support a new layer.
  • The existing roof is slate, clay tile or concrete tile.
  • The roof is wood shakes, in most cases.

Check with your township or borough

Municipalities around Harrisburg handle residential re-roofing differently. Some ask for a permit for any tear-off, some only when the decking or structure is involved, and some have their own limits on layers. Lower Paxton, Susquehanna Township, Camp Hill and Mechanicsburg each set their own process. See Pennsylvania roof permits for how to ask.

What a roof-over hides

The case for a full tear-off is mostly about what the crew can see once the old shingles are gone. On older Harrisburg, Steelton and Hershey houses, that is often where the surprises are.

  • Soft or rotted decking from years of small leaks, which gets replaced before anything new goes down.
  • Missing or worn-out ice barrier at the eaves, which matters on central Pennsylvania roofs every winter.
  • Rusted or patched flashing at chimneys, walls and valleys, which can be replaced properly only with the shingles off.
  • Old plank decking with wide gaps, common on pre-war houses, that may need new sheathing.

What you give up by roofing over

A second layer adds a lot of weight to the rafters. Shingles laid over a lumpy old roof tend to show every ridge and dip underneath, and they can run hotter because they sit on old asphalt rather than a flat deck. Many shingle makers also set stricter terms for products installed over an existing layer, so read the product paperwork before deciding.

When the time comes to replace a two-layer roof, both layers have to come off at once, which makes that future job bigger.

When a roof-over can make sense

A single layer of asphalt shingles that lies flat, with sound decking, good flashing and no history of leaks, is the usual candidate. Some homeowners choose it for a garage or a house they plan to sell soon. For a house you intend to keep, most roofers in the area recommend tearing off so the deck and the eaves can be inspected and done right.

Attic first

Before choosing, look at the underside of the roof from the attic. Dark stains, soft spots or daylight point toward a tear-off. See signs you need a new roof and attic ventilation and condensation.

Questions

+How many layers of shingles can a house in Pennsylvania have?

The residential code used in Pennsylvania allows at most two layers of asphalt shingles. If a roof already has two, the next replacement needs a full tear-off. Your municipality may be stricter.

+How can I tell how many layers my roof has?

Look at the edge of the roof at the gutter or a gable end from a ladder, or ask the roofer to check. Each layer shows as a separate thickness of shingle along the drip edge.

+Can metal roofing go over old shingles?

Some metal systems are designed to go over one layer of shingles, usually on battens or an underlayment. The same weight and decking questions apply. See [slate and metal roofs](/roofing-guide/slate-and-metal).

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