Tear Off the Old Roof or Shingle Over It? A Massachusetts Guide

What the code allows

Massachusetts bases its residential building code on the International Residential Code. Its re-roofing rules allow a new layer of asphalt shingles over one existing layer in some cases, and require a full tear-off in others.

• The roof already has two or more layers
• The existing roofing is water-soaked or too deteriorated to support a new layer
• The existing roof is slate, clay tile or concrete tile
• The existing roof is wood shakes, in most cases

Either way, the job generally needs a building permit, and the building department may have its own views. See permits and licenses.

What a roof-over hides

On older houses in Springfield, Chicopee and Holyoke, the case for tearing off is mostly about what can be seen once the old shingles are gone.

• Soft or rotted decking from slow leaks or attic condensation
• Missing or failed ice barrier at the eaves, the main protection against ice dams
• Rusted or tarred-over flashing at chimneys and walls
• Old plank decking with wide gaps, or wood shingles still underneath

A roof-over leaves all of that in place. The ice barrier is a particular concern in western Massachusetts: the code calls for it at the eaves, and it has to be applied directly to the deck.

What you give up by roofing over

• Extra weight on the rafters, which matters under a heavy snow load
• New shingles that show every bump and dip in the old layer
• Shingles that may run hotter sitting on old asphalt
• A bigger job next time, when both layers have to come off together
• Possible limits on the shingle maker's coverage for products installed over an existing layer

When a roof-over can make sense

A single, flat-lying layer of asphalt shingles over sound decking, with good flashing and no leak history, is the usual candidate. Some owners choose it for a detached garage or shed. For a house you plan to keep, most roofers around Springfield recommend tearing off so the deck, ice barrier and flashing can be done properly.